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112785

3701662

On Furfuraniline and Furfurtoluidine

537

542

Proceedings of the Royal Society of London

John Stenhouse

fla

6.0.4

http://dx.doi.org/10.1098/rspl.1869.0092

proceedings

http://corpora.clarin-d.uni-saarland.de/surprisal/6.0.3/?id=112785

10.1098/rspl.1869.0092

http://www.jstor.org/stable/112785

Chemistry 2

Chemistry 1

Chemistry

VIII . C On Furfuraniline and Furfurtoluidine . " By JOHN STENHOUSE , LL. D. , F.R.S. Received May 19 , 1870 . In an epistolary communication to Mr. H. Watts *I stated that " The most abundant and economical source of furfurol is in the preparation of garancin by boiling madder with sulphuric acid . If the wooden boilers , in which garancin is usually manufactured were fitted with condensers , furfurol might be obtained in any quantity without expense . Furfurol is also produced by boiling any kind of madder with solution of sulphate of aluminium . Crude furfurol , whether obtained from madder , bran , sawdust , or any other of its usual sources , is always contaminated with another aromatic oil , which I called metafurfurol . This has a higher boiling-point , and oxidizes more readily than furfilrol , so that by repeated rectification almost the whole of it is converted into a brown resinous matter , which remains in the retort . It is owing to the presence of this impurity that crude furfurol so rapidly changes its colour when kept , the metafurfurol not only being itself decomposed , but superinducing the oxidation of the furfurol . A much simpler and more effective method , however , of purifying furfurol from this substance consists in digesting it for some hours with very dilute sulphuric acid , to which small quantities of acid potassium chromate are added from time to time ; this effectually destroys the metafurfurol and other impurities , so that the furfurol which distils over after being separated from the water and dried over fused chloride of calcium has a constant boiling-point of 161 ? C. It has a much more agreeable odour than before , is nearly colourless , and may be exposed to the air under a layer of water for months , without any considerable increase of colour . Its refractive index for the D line at 20 ? C. is 1'520 t. Action of Fue furol on Aniline Furfuraniline . Twenty years ago +I stated that when aniline was added to furfurol , the mixture acquired a rose-red colour , which it communicated to the skin , and likewise to paper , linen , and silk , but that these rapidly lost their colour , becoming of a brownish yellow , even when light was excluded . I was unable , however , to obtain this red substance in a crystalline state . In 1860 the subject was again examined by M. Jules Persor ? , who dissolved aniline in acetic acid , and then added an excess of aqueous solution of furfurol ; after some time a deep red viscid mass was deposited on the sides of the vessel , which communicated to silk and wool a fine but very fugitive red colour . Ile was not more fortunate than I had been in obtaining this substance in a crystalline state . A few months ago I resumed the investigation of this subject , and although I was unable to obtain definite compounds either by the action of furfurol on aniline itself or on its salts when in a pure state , yet when furfurol was added to a strong alcoholic solution of aniline hydrochlorate containing an excess of aniline a deep red colour was produced , and in the course of a few minutes the mixture solidified to a crystalline mass of a fine iridescent purple colour . Ann. Chem. Phar . lxxiv . 282 . tI am indebted to the kindness of Messrs. T. acnd I. Smith , of Edinburgh , for the greater portion of the furfurol employed in this investigation . This firm has long been in the habit of manufacturing it for preparing furfurine for medical purposes . + Ann. Chem. Pharm. lxxiv . 282 . ? Rep. Chem. App. 1860 , p. 220 . Dr. J. Stenhouse on 538 [ June 16 , Furfuraniline hydrochlorate.-The best method of preparing this salt was to dissolve 46 parts aniline and 65 parts aniline hydrochlorate in 400 parts of warm alcohol , and then add 48 parts furfurol , likewise dissolved in 400 parts spirit ; after the solutions were thoroughly mixed , they solidified in the course of a few minutes to a mass of crystals of the salt . When cold , these were thrown on to a filter , freed from the mother liquor by means of a vacuum filter , and washed with a small quantity of coloured spirit . They were then readily obtained in a pure state by recrystallization from boiling spirit . The substance analyzed was dried in vacuo . I. '207 grm. substance gave *488 grm. carbonic anhydride and '120 grm. water . II . '158 grm. substance gave '372 grm. carbonic anhydride and '082 grm. water . III . '228 grm. substance gave '103 grm. argentic chloride . IV . '282 grm. substance gave '128 grm. argentic chloride . V. '0448 grm. substance gave '003773 grm. nitrogen . Theory . I. II . II . IV . V. Mean . C01= 204 64-05 64-30 64-21 ... ... ... ... ... . . 64-25 H19= 19 5-97 6-44 5-77 ... ... ... ... ... . 6-10 02 32 10-05 ... ... ... ... ... ... ... ... ... ... N2 28 8-79 ... ... ... ... ... ... 8-42 8-42 l 35-5 11-14 11 ... ... . . 11-18 11-23 ... ... 11-20 318-5 This corresponds nearly to the formula C , H18 O2 N2 , C1 H. It is insoluble in benzol , bisulphide of carbon , and water , but is slowly decomposed when boiled with the latter . It is soluble in boiling spirit , and crystallizes out on cooling in small needles of a fine purple colour , which acquire a metallic lustre on drying . The crystals are permanent in dry air when light is excluded , but are readily decomposed when boiled with dilute acids or alkalies . Furfuraniline nitrate.-This is prepared in a manner similar to that employed for the hydrochlorate : 23 parts aniline and 39 of nitrate were dissolved in 200 parts warm spirit , and 24 parts furfurol in 200 of spirit added . The mixture , on being allowed to stand some time , became a semisolid crystalline mass , which was purified in the same manner as the corresponding hydrochlorate . I. '289 grm. substance gave '628 grm. carbonic anhydride and *157 grm. water . C1 , =204 -1 =19 N , =42 0 , = 80 345 Theory . 59-13 5051 12-17 23-19 100-00 TL 59'28 6'04 This nitrate is therefore C , 1118 N2 O , NO3 tI . It resembles the hydrochlorate in its properties , but is much more soluble in boiling spirit , and forms larger crystals . Furfuraniline sulphate.-When 23 parts aniline and 35 of its sulphate were dissolved in 3000 of boiling alcohol , and 24 parts of furfurol in 200 of boiling spirit added , the mixture became deep red , and on cooling deposited minute purple needles of the furfuraniline sulphate , contaminated , however , with colourless crystals of aniline sulphate . When an attempt was made to separate these by crystallization from alcohol , the furfuraniline salt was mostly decomposed , with formation of aniline sulphate , which crystallized out . Furfuraniline oxalate.-When aniline oxalate of aniline and furfurol were dissolved in spirit , as in the preparation of the salts above described , the solution became of a deep red colour , but did not yield crystals of oxalate of furfuraniline , only oxalate of aniline and a dark red tarry matter being produced . Furfuraniline . In order to obtain this base , a salt of furfuraniline ( the hydrochlorate or nitrate ) was ground up to a paste with water and strong aqueous ammonia added , the whole being intimately mixed until the purple colour disappeared , giving place to a pale brown . Warm water was then added until the liberated base became soft and plastic , so that it could be needed in successive quantities of warm water , in order to remove the ammoniacal salts and free ammonia . The base , as thus prepared , has much the pale brown glossy appearance of stick lac , and , like it , can be drawn out into strings when soft . It is insoluble in water , but very soluble in ether and alcohol , and when hydrochloric acid is added to a strong spirituous solution it becomes deep red , and solidifies in a few moments to a mass of the purple crystals of the hydrochlorate . The base decomposes , however , very rapidly when exposed to the air , or when boiled with alcohol , and will then no longer yield crystalline salts with acids . The same effect takes place , but more slowly , in a vacuum . Action of FuSfurol on Toluidine Furfurtoluidine . When alcoholic solutions of toluidine and furfurol were mixed , there was no immediate change ; but after standing some time they acquired a red colour : asin the corresponding reaction with aniline no crystalline sabstance was produced . Furfurtoluidine hydrochlorate.-The method employed to obtain this salt was similar to that used in preparing furfuraniline hydrochlorate : 12 parts toluidine hydrochlorate and 9 parts crystalline toluidine were dissolved in 150 parts hot spirit , and 8 parts of furfurol dissolved in 150 parts spirit added ; the mixture acquired a deep-red colour , and on cooling became a mass of minute acicular crystals closely resembling in appearance the furfuralinine salt . It was purified by recrystallization from boiling alcohol , dried in vacuo , and analyzed . [ June 16 , 540 Dr. J. Stenhouse on I. *232 grm. substance gave *562 grm. carbonic anhydride and '135 grm. water . Theory . I. Cl1 = 228 65-80 66-07 H2,3= 23 6-64 6'47 02 = 32 9'24 ... . N2= 28 808 . C1 = 35 5 10'24 ... . 346-5 100-00 This corresponds to C , , H11 02 N2 , C1 I. Furfurtoluidine nitrate.-This was prepared in a manner similar to the hydrochlorate , substituting the equivalent proportion of toluidine nitrate : 14 parts toluidine nitrate and 9 parts toluidine were dissolved in 100 parts hot alcohol , and 8 parts furfurol in an equal quantity ( 100 parts ) of spirit added ; after standing some time the nitrate crystallized out in deep purple needles . When purified and analyzed it gave the following numbers : I. '160 grm. substance gave 355 grm. carbonic anhydride and -098 grm. water . Theory . I. C19 =228 61'12 60-52 1123= 23 6-17 6-81 0= 80 21-45 ... . N3 = 42 11-26. . 373 100-00 It has therefore the composition C11 H22 N , NO , I-I . Furfurtoluidine.-The salts of furfurtoluidine , when treated with ammonia solution , were decomposed in a manner similar to that already described under the head furfuraniline , but not quite so readily . The crude free furfurtoluidine , when digested with ether , dissolved , and on filtering the solution , distilling off the ether , and drying the residue in a vacuum over sulphuric acid , the base was obtained as a brown amorphous mass , which is brittle and easily reduced to powder . It is not as fusible as furfuraniline , and is far less readily decomposed . A carbon and hydrogen determination of the freshly prepared base , purified by ether and dried in vacuo , gave the following results : I. '243 grm. substance gave -660 grm. carbonic anhydride and '159 grin . water . Theory . I. C1== 228 73-54 74-08 122= 22 7-11 7'27 02 = 32 10'32 . N2= 28 9-03 310 100-00 This corresponds pretty nearly with the formula C9 , , H22 , 0 , N , . Both furfuraniline and furfurtoluidine resemble rosaniline in giving beautifully coloured salts , whilst the bases are nearly colourless , or of a pale brown colour . Furfurnaphthylamzine.-VWhen an alcoholic solution of furfurol was added to a similar solution of naphthylamine it immediately became of a red colour , which is as fugitive as the one obtained from aniline , but much duller . Several attempts were made to prepare crystalline salts of this compound , but without success , only dark-coloured resinous substances being obtained . Several other typical bases were also tried , but without any results . These were quinidine , coniine , sparteine , and theine . It appears , therefore , from these experiments , that it is only the bases of the aromatic series which combine with furfurol to yield these peculiar-coloured salts in a crystalline state . I cannot conclude this paper without acknowledging the very efficient aid I have received from my assistant , Mr. Charles Edward Groves , in the preceding investigation .

112786

3701662

On Parasulphide of Phenyl and Parasulphobenzine

542

543

Proceedings of the Royal Society of London

John Stenhouse

fla

6.0.4

http://dx.doi.org/10.1098/rspl.1869.0093

proceedings

http://corpora.clarin-d.uni-saarland.de/surprisal/6.0.3/?id=112786

10.1098/rspl.1869.0093

http://www.jstor.org/stable/112786

Chemistry 2

Reporting

Chemistry

IX . E'On Parasulphide of Phenyl and Parasulphobenzine . " By JOHN STENHOUSE , LL. D. , P.R.S. , &c. Received May 27 , 1870 . When sulphideofphenyl , C6H5 } S , was passed several times in succession 6 5 . through an iron tube filled with nails and heated to low redness , a considerable amount of carbonaceous matter was deposited , and a portion of the sulphide was converted into an isomeric compound , which I propose to call Parasulphide of Phenyl . In order to obtain this substance from the dark-coloured distillate which collected in the receiver when sulphide of phenyl was submitted to the action of heat in the manner above described , it was transferred to a copper retort and distilled . The clear dark-yellow oil was then cooled for several hours in a freezing-mixture , when a considerable quantity of a white crystalline substance separated in nodules ; this is freed from undecomposed sulphide of phenyl by thoroughly draining it on a vacuum filter . It can readily be purified by repeated crystallization from boiling alcohol , in which it is rather soluble . I. '197 grm. substance gave *557 grm. carbonic anhydride and *092 grm. water . II . *166 grm. substance gave ? 473 grm. carbonic anhydride and '077 grm. water . III . *200 grmo substance gate '254 grm. barium sulphate . IV . *218 grm. substance gave '276 grm. barium sulphate . 542 [ June 16 , Theory . I. II . III . IV . Mean . C , = 144 77-41 77-13 77'73 ... . 7743 H1O = 10 5-38 5'19 5'15 ... . 517 S= 32 17-21 ... . 17-43 17-37 17-40 186 10000 This corresponds to the empirical formula C12 H1o S. Parasulphide of phenyl crystallizes from alcohol in small white needles , which melt at 94 ? C. , and can be distilled at a very high temperature . It is insoluble in water , but rather soluble in bisulphide of carbon , ether , and benzol . Parasulphobenzine.-When parasulphide of phenyl was digested for several hours with dilute sulphuric acid and acid chromate of potassium , it was gradually converted into a new substance , having a much higher melting-point , so that the completion of the oxidation was readily observed by the entire disappearance of the fused parasulphide . The crude parasulphobenzine was then collected , well washed with water , and purified by two or three crystallizations out of boiling alcohol . I. *194 grm. substance gave -470 grm. carbonic anhydride and *075 grm. water . IT . '347 grm. substance gave '843 grm. carbonic anhydride and -138 grm. water . Theory . I II . Mean . C12=144 66-06 66-09 66-27 66-18 Hl-= 10 4-58 4-30 4-42 4-36 S= 32 14'68 02= 32 14-68 100-00 These carbon determinations correspond with the formula C12 IH1o SO ' ; it has therefore the same percentage composition as the sulphobenzine obtained by the oxidation of sulphide of phenyl * . Parasulplobenzolene melts at 230 ? C. , is soluble in boiling alcohol , from which it crystallizes on cooling in the form of long white shining needles . It is insoluble in water , soluble in benzol , ether , and carbon disulphide . It dissolves readily in warm sulphuric acid , forming a colourless solution , and does not blacken even when heated to the boiling-point of the acid . Water precipitates it unchanged . It is also soluble in hot strong nitric acid without change , and crystallizes out on cooling . r Proc. Roy . Soc. vol. xiv . p. 351 . 2s2 1870.1 543

112787

3701662

On a Method of Graphically Representing the Dimensions and Proportions of the Teeth of Mammals

544

546

Proceedings of the Royal Society of London

George Busk

fla

6.0.4

http://dx.doi.org/10.1098/rspl.1869.0094

proceedings

http://corpora.clarin-d.uni-saarland.de/surprisal/6.0.3/?id=112787

10.1098/rspl.1869.0094

http://www.jstor.org/stable/112787

Anatomy 2

Tables

Anatomy

X. " 1 On a Method of graphically representing the Dimensions and Proportions of the Teeth of Maammals . " By GEORGE BUSK , F.R.S. Received May 20 , 1870 . Of all the hard parts of animals , the teeth , more especially for palkeonltological purposes , undoubtedly afford the most constant and the most generally available characters . Any plarn , therefore , by which the study and ready comparison of these organs may be facilitated and simplified cannot fail to be of some use to the zoologist and paleontologist . Having myself found the method I am about to describe convenient in many instances , more particularly in the case of fossil mammals , I have been led to believe , by the representations of several to whom it has been communicated , that it might be found useful by others , and consequently , though at first sight but a triflinrg matter , worthy of a place in the ' Proceedings ' of the Society . The characters afforded by the teeth are derived from their number , proportions ( absolute and relative ) , and pattern . In many cases the pattern of the teeth must undoubtedly be taken into account ; but in a very great number it will be found that the number and proportions , more particularly of the premolars and molars , are sufficient for the purpose of diagnosis , or , at any rate , that a knowledge of these particulars alone will reduce the necessity for further comparison within a small compass . A good illustration of this is afforded in the smaller Felidse , in which , owing to their high specialization , the pattern of the teeth is in the main so very closely alike as to render it of very little assistance in diagnlosis , though not altogether . The statement of the particulars above mentioned , in words or figures when numerous comparisons are needed , is tedious and laborious to both writer and reader ; and even in the most carefully arranged tables it is difficult without close attention to perceive at once differences which though minute are , from their constancy , important and in fact necessary for the diagnosis of nearly allied forms . My plan may be termed one for the graphic or diagrammatic representation of the absolute and relative or proportional dimensions and number of the premolar and molar teeth , or of those constituting the molar series , and which have appeared to me in most cases sufficient for the purpose in view . But of course the incisors and canines might be included in the scheme if thought requisite . The method in which these " odontograms " are prepared will be at once obvious on inspection of the accompanying examples . Each horizontal line in the figures , which represent the maxillary and mandibular molar series of a species , corresponds to a single tooth , whose extreme length or antero-posterior diameter is indicated by the extent of the lighter shade , and its extreme breadth or transverse diameter by the darker shade . Both dimensions are , of course , measured from the same base-line . The respective measurements , which may be taken with a pair of sharppointed caliper-compasses , having been pricked out upon the equidistatit horizontal lines , the points showing the length and breadth of each tooth are connected by straight lines , and a sort of figure is thus obtained which , in nearly all cases , will be characteristic of the genus or family , and in many instances sufficient to determine the species also . In some cases , as for instance in Canis and Viver ra , the odontograms are at first sight so nearly alike that recourse must be had to the pattern of the teeth in addition , as before alluded to . In order to render figures of this kind easily comparable inter se , it is necessary that they should be drawn upon some common scale for the distance between the horizonal lines . This is , of course , entirely arbitrary , all that is requisite being that it should not be too great nor too small . The aceompanying odontograms are drawn upon a scale of '25 inch= 6'35 mnm . , which appears convenient for the purpose ; and is suitable for all teeth of the dimenisions that readily admit of this mode of definition , that is to say , which are neither too large , as those of the Elephant , nor too small , as in the smallest mammals . Moreover , if the figures are drawn upon ruled paper , the actual measurement of the size of the teeth can be read off at sight ; and with this object I have employed paper ruled to a scale of -05 inch . The examples selected to show the application of the method above described have necessarily been limited to a very few . They include figures of the delntition of the Lion and Tiger , taken from the largest specimens of each species I have as yet met with ; but they afford a fair illustration of the way in which even a slight specific difference is brought out , and which , in the case of these animals , is almost confined to the lower teeth . The three odontograrns of the genus Ursus represent the mean dimensions and proportions taken from numerous instances of each species , and they show at a glance the differences between them . In these the small anterior premolars have been purposely omitted to save space . The odontograms of Hycena are of the same kind . The dentition of the genus Canis is exemplified by instances taken from the Wolf to the Fennec Fox , or from the largest to the smallest species , in order to illustrate the uniformity of the generic type throughout ; and amongst these forms , two will serve to show how the method may be used in palseontological research . Plate IX . fig. 13 represents the dentition of the fossil Fox described by Messrs. Durand and Baker from the Siwalik HIills , and fig. 14 that of the existing Canis bengalensis , which would thus appear to be the close representative of its ' supposed miocene progenitor , a resemblance which further comparison of the skulls only serves to render still more obvious . The other fig , ures are introduced merely to indicate the variety of forms produced in this way from the measurements of the teeth Qf different genera . DESCRIPTION OF THE PLATES . PLATE VIII . PLATE IX . Fig. 1 . Felis leo ( max . ) . Fig. 10 . Canis lupus . 2 . ligris ( max . ) . 11 . aureus . 3 . -jubata ( mean ) . 12 . vulpes . 4 . Ursus ferox ( mean ) . 13 . bengalensis ( fossilis ) . 5 . arctos ( mean ) . 14 . ( body ) . 6.maritimus ( mean ) . 15 . zerda . 7 . IHyena crocuea ( mean ) . 16 . Sus scrofa ( ferus ) . 8 . brunnea ( mean ) . 17 . domesticus . 9 . striata ( mean ) . 18 . Egqcus caballus .

112788

3701662

Note on the Spectra of Erbia and Some other Earths

546

553

Proceedings of the Royal Society of London

William Huggins

fla

6.0.4

http://dx.doi.org/10.1098/rspl.1869.0095

proceedings

http://corpora.clarin-d.uni-saarland.de/surprisal/6.0.3/?id=112788

10.1098/rspl.1869.0095

http://www.jstor.org/stable/112788

Atomic Physics

Chemistry 2

Atomic Physics

XI . " Note on the Spectra of Erbia and some other Earths . " By WILLIAM HUGGINS , LL. D. , F.R.S. Received May 26,1870 . Bahr and Bunsen have shown* that erbia , rendered incandescent in a Bunsen 's gas-flame , gives a spectrum of bright lines in addition to a brilliant continuous spectrum . As they were unable to discover the bright lines in the flame beyond the limits of the solid erbia , they suggest that the light which is dispersed by the prism into bright lines is emitted by the solid erbia , which substance therefore appears to stand alone , as a remarkable exception , among solid bodies . Bahr and Bunsen found the spectrum of bright lines to coincide very nearly with the absorption spectrum of some compounds of erbium . A few weeks since , when in Ireland , I made the observation that the spectrum of the ordinary lime-light contains bright linest . Dr. Emerson Reynolds , Director of the Laboratory of the Royal Dublin Society , kindly undertook to make experiments to ascertain from the position of the lines if they were due to the cylinder of lime , or to impurities contained in it . Upon my return to town I made the following experiments ; shortly after commencing them I received from Dr. Reynolds the account of his experiments , which , with his permission , I have added to this note . Erbia.-A few months since I received , through the kindness of Dr. Rooscoe , F.R.S. , a few grains of nitrate of erbia , which he had procured from a trustworthy source . I followed Bunsen 's method of placing it with syrupy phosphoric acid upon a platinum wire . The erbia , obtained by this method in a finely divided state , was then submitted to the heat of the oxyhydrogen blowpipe . In all the experiments described in this paper hydrogen alone was first turned on , and the effect of the heat of the flame on the substance under examination observed with the spectroscope . Oxygen was then admitted slowly , and the effect of the increased heat carefully noted . With the flame of hydrogen alone , the lines represented in the map 4 + +9 -S 4+ _ . _.f _K + ... ._ -qff-ml+ 44-4 t W4 44=4 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~fT -I , 1= : + 24:-1 r4 T+-L|+~~~~~~~t r I44-~~~..ilt A -L_rLI -i ; r'l7J'~ ? % --s ' ~~~~~~~~~~~~~~~~~~~~~~~~~~~~i I i[ & trtrq ( t7 m+ t-S L4t+$S t44+- < -+4-r44---4-4 > -S-'4aX-tl OOEXOY00f ! tet tit- ; r 41 , l 2 , . > .j WW t=t+ > W : > mtt : : > .:lzE4 r r_h:~~~~~~~~~~~~~~~~~~.I ve 1u Si- . _~t 1§ 4 §§j g4= ' ? t-11__ 44 0 ; tl X , 1L eg~~~~~~~~~~~~ te +i4+e + 9i 1L . ; I1_ , LA . IX rti . l14^ tA L. Il-i , l , %i 11 ) } . , ,Xt,.1 ) t4:IL , f ... _l..1.s1 . i~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ lLA-aS ' XoA a-oS Aog aH~~~~~ which accompanies Bahr and Bunsen 's paper were seen , but the lines were more distinct when a small proportion of oxygen was admitted . With the full proportion of oxygen , the light from the glowing erbia was more intense , but the lines were not so well seen . Even with the intense heat of the oxyhydrogen flame I was unable to trace the lines beyond the limits of the solid erbia , though the line of sodium could be seen for some distance from the erbia . I found , however , that the lines appeared more distinct , in consequence , probably , of their being brighter relatively to the parts of the continuous spectrum where they occur , when the slit was directed from the side upon the gas immediately in front of the glowing part of the erbia . The spectrum of bright lines obtained by means of the oxyhydrogen flame agreed more completely with the absorption spectrum represented by Bahr and Bunsen ( No. 2 in their diagram ) than the spectrum of bright lines figured by those observers ( No. 3 ) . The most important differences occurred in the band in the red , which showed two points of greatest brightness , thus forming a double line with a little outstanding light , and the line in the green at 65 of the scale , which was double , precisely as the corresponding absorption-line is represented in spectrum No. 2 of the diagram . Lime.-The experiments were made with the cylinders of lime prepared for use with the oxyhydrogen blowpipe , and also with pieces of pure caustic lime , but there was no sensible difference presented in the spectroscope . The bright lines consisted of a double line in the green , and several bands in the orange and red , which were found to form a spectrum identical with that which is produced when chloride of calcium is heated in the flame of a Bunsen 's burner . When the spectroscope was directed to a point in the flame a little above the incandescent portion of the lime , the lines appeared beyond the bright continuous spectrum , showing that they are not produced by the white-hot solid lime , but by the luminous vapour into which a portion of the lime has been converted by the heat of the flame . Magnesia.-The commercial heavy oxide of magnesium was made into a paste with distilled water , and formed into a small pellet upon the end of a platinum wire . The pellet of magnesia was slowly dried , and then placed in the oxyhydrogen flame . I was surprised to see a spectrum of bright lines precisely similar to that which is produced by lime . Chloride of magnesium , when introduced into the Bunsen flame , gave a similar spectrum . I record these results as the oxide and chloride were those sold as pure . I found afterwards that a very small trace of lime may be detected in magnesia by means of the oxyhydrogen flame . I then took metallic magnesium , which I had found by the spectroscope to be nearly pure , and formed from it magnesia and chloride of magnesium . When this magnesia , formed into a small ball upon a wire , was sub jected to the oxyhydrogen flame , two bright bands were seen in the green . One of these was found to be coincident with the triple line of Fraunhofer 's b , which distinguishes magnesium , and the other with a group of bright lines which is seen between b and F , nearly in the position of the brightest double line of nitrogen , when metallic magnesium is burnt in air . The chloride formed from magnesium , when introduced into the Bunsen flame , gave the same bands , but the more refrangible band was exceedingly faint . When an induction-spark was taken from a wire covered with cottonwool soaked with a solution of the chloride , the lines at b and the more refrangible group were seen . If the heating-power of the spark be increased by the introduction of a Leyden jar , the band between b and F becomes scarcely distinguishable , while the lines peculiar to metallic magnesium are much more intense . When a spark is taken between electrodes of the same specimen of magnesium from which the chloride was formed , no trace of this band was detected . Baryta.-When pure caustic baryta is subjected to the heat of the oxyhydrogen flame , a brilliant spectrum is seen identical with the wellknown spectrum which presents itself when chloride of barium is heated in the Bunsen flame . Baryta furnishes a larger quantity of vapour than lime and magnesia , and therefore the lines could be traced to a greater distance from the solid baryta . Strontia.-Pure strontia was fused into a large bead upon a platinum wire . When this bead was heated by the oxyhydrogen flame , the same spectrum of bright lines presented itself as is seen when chloride of strontium is placed in the flame of a Bunsen 's burner . Zirconia , -One of the small pellets of zirconia prepared in France for use with the oxyhydrogen blowpipe was found to give no trace of bright lires . This great fixity of zirconia as compared with lime is in agreement with the inalterability of the substance under the action of the oxyhydrogen flame . Allumina.-Pure alumina treated in the same way as the magnesia gave a continuous spectrum only , without any trace of bright lines . Glucina.-Glucina gave a bright line in the red , which I found to be due to potassium . Glucina , therefore , appears not to form vapour of any kind under the heat of the oxyhydrogen blowpipe . Titanic acid gave a continuous spectrum without lines . Oxide of uranium a continuous spectrum without lines . Tungstic acid a continuous spectrum without bright lines . Molybdic acid a continuous spectrum without bright lines . Silica ( precipitated ) a continuous spectrum without bright lines . Oxide of cerium a continuous spectrum without bright lines . The question presents itself as to the nature of the vapour to which the bright lines are due in the case of the earths , lime , magnesia , strontia , and baryta . Is it the oxide volatilized ? or is it the vapour of the metal reduced by the heat in the presence of the hydrogen of the flame ? The experi ments show that the luminous vapour is the same as that produced by the exposure of the chlorides of the metals to the heat of the Bunsen gasflame . The character common to these spectra of bands of some width , in most cases gradually shading off at the sides , is different from that which distinguishes the spectra of these metals when used as electrodes in the metallic state* . Roscoe and Clifton have investigated the different spectra presented by calcium , strontium , and barium , and they " suggest that at the lower temperature of the flame or weak spark , the spectrum observed is produced by the glowing vapour of some compound , probably the oxide , of the difficultly reducible metal ; whereas at the enormously high temperature of the intense electric spark these compounds are split up , and thus the true spectrum of the metal is obtained . In none of the spectra of the more reducible alkaline metals ( potassium , sodium , lithium ) can any deviation or disappearance of the maxima of light be noticed on change of temperature " . 4 As the experiments recorded in this paper show that the same spectra are produced by the exposure of the oxides to the oxyhydrogen flame , Roscoe and Clifton 's suggestion that these spectra are due to the volatilization of the compound of the metal with oxygen is doubtless correct . The similar character of the spectrum of the bright lines seen when erbia is rendered incandescent would seem to suggest whether this earth may not be volatile in a small degree , as is the case with lime , magnesia , and some other earths . The peculiarity , however , of the bright lines of erbia , observed by Bahr and Bunsen , that they could not be seen in the flame beyond the limits of the solid erbia , deserves attention . My own experiments to detect the lines in the Bunsen gas-flame , even when a very thin wire was used , so as to allow the erbia to attain nearly the heat of the flame , were unsuccessful . The bright line in the green appears , indeed , to rise to a very small extent beyond the continuous spectrum , but I was unable to assure myself whether this appearance might not be an effect of irradiation . It is perhaps worthy of remark that the chlorides of sodium , potassium , lithium , caesium , and rubidium give spectra of defined lines which are not altered in character by the introduction of a Leyden jar , and which , in the case of sodium , potassium , and lithium , we know to resemble the spectra obtained when electrodes of the metals are used . Now all these metals belong to the monad group ; it appeared therefore interesting to observe the behaviour of the other metal belonging to this group . Chloride of silver when introduced into the Bunsen flame gave no lines . The chloride was then mixed with alumina , which had been found to give a continuous spectrum only , and exposed to the oxyhydrogen lame , but no lines were visible . When , however , the moistened chloride was placed on cotton and subjected to the induction-spark without a jar , the true metallic spectrum was seen , as when silver electrodes are used . The behaviour of silver , therefore , is similar to that of the other metals of the monad group . Now the difference in basic relations which is known to exist between the oxides of the monatomic and polyatomic metals would be in accordance with the distinction which the spectroscope shows to exist in the behaviour of the chlorides ; the chlorides of the polyatomic metals would be more likely to split up in the presence of water into oxides and hydrochloric acid . In the case of some of the oxides and chlorides , one or more of the lines appeared to agree with corresponding lines in the metallic spectra ; it may be , therefore , that under some circumstances , as in the case of magnesium burning in air , the metallic vapour and the volatilized oxide may be simultaneously present . Dr. Reynolds'sY Experiments . " After you observed the occurrence of two bright lines in the spectrum of the light emitted by incandescent lime , you recollect we identified these as belonging to calcium . At the time we supposed that these lines were produced by the ignition of the vapour of some volatile calcium compound probably present as an impurity in the sample of limes used in the experiments . If this explanation was found to be true for lime , the bright lines seen in the spectrum of erbia might possibly be accounted for in a similar manner . In order to examine the matter fully , I arranged the experiments described below . " I selected two oxides for comparison with erbia , viz. lime and magnesia . As it seemed desirable to prepare these oxides in precisely the same manner as the erbia , some calcium and magnesium nitrates were made chemically pure to ordinary tests , and then used in the preparation of the respective oxides . " Tile oxyhydrogen flame was employed as the chief source of heat . The hydrogen was made from zinc and sulphuric acid in the usual way , and the oxygen from potassium chlorate . As both gases are certain to be contaminated with traces of acids , I took the precaution of passing each gas through a long tube filled with fragments of solid potassium hydrate . If this plan were not adopted , the traces of acid which would find their way into the hydrogen or oxyhydrogen flame might produce volatile compounds with the earths , and so lead to mistakes . " 1 . Experiments with Magnesia.-A loop of stout platinum wire was moistened with syrupy phosphoric acid , and some magnesium nitrate made to adhere . The nitrate was then heated in the hydrogen flame , and a residue of magnesia obtained . No lines were observed in the spectrum of the light emitted by the incandescent earth , and when the latter was in . 550 [ June 16 , tensely heated in the oxyhydrogen jet only a continuous spectrum was seen* . " 2 . Experiments with Lime.-A platinum wire of the same thickness as the last was moistened with the phosphoric acid , some calcium nitrate was then taken up in the loop , and heated in the hydrogen flame until a residue of lime was obtained . At the outset the calcium-spectrum was observed , but the light speedily gave only a continuous spectrum . The lime and loop of wire were kept well enveloped in the hydrogen flame for nearly half an hour in order to ensure the complete decomposition of the nitrate . During this time no lines could be detected on the background of the continuous spectrum , or in the spectrum of the flame surrounding the lime . More hydrogen was now turned on and oxygen slowly admitted , the liglt being examined with the spectroscope during the time . When the proportion of oxygen had reached a certain point , faint traces of the two brightest Ca lines appeared on the bright background , and the intensity of these lines increased with the amount of oxygen admitted up to a definite extent . When a certain proportion of oxygen was exceeded , the lines became less distinct . The best results were obtained when the hydrogen was decidedly in excess of the oxygen in the flame , that is to say , more than in the proportion of 2 : 1 . " When the slit of the spectroscope was pointed in such a way that only the light from the flame surrounding the incandescent lime entered the instrument , all the Ca lines and bands were observed with great ease without a continuous spectrum . On looking at the mantle of flame with the naked eye it was easy to perceive a reddish tinge . I next maintained the small fragment of lime at the highest temperature its supporting wire was capable of resisting for three hours ; at the end of this time the Ca lines were as strongly marked as before , and the lime on the wire had very appreciably diminished in amount . The same results were obtained when no phosphoric acid was employed to attach the calcium nitrate to the wire in the first instance . " Again , a piece of well-burned quicklime , of very small size , was heated alone on a platinum wire for more than an hour , and the bright Ca lines were seen during the whole time . " From the results of these experiments , we must draw the conclusions ( ) that when lime is sufficiently heated the light which it emits is derived in part from the incandescent solid , and partly from ignited vapour ; ( 2 ) that lime is either volatile as such , or that in the first instance it suffers reduction by the excess of hydrogen in the flame , the luminous vapour of calcium then giving its own peculiar spectrum . " 3 . Experiments with Erbia.-The specimen of erbium nitrate which you kindly gave me was attached to a platinum loop with syrupy phosphoric acid as usual , and decomposition of the salt effected in the plain hydrogen flame . After heating for a short time in this way , the chief green line of erbia became visible , but seen upon the continuous spectrum . Oxygen was now turned slowly into the flame . As the temperature rose , two of the other bright lines of the earth were seen . The best observations were made when the oxyhydrogen flame had hydrogen in excess , and the erbia was kept in such a position that it was very strongly ignited . The erbia lines were most distinctly seen when the slit of the spectroscope took in the light from the extreme edge of the incandescent solid . When the bright lines were best observed , the continuous spectrum was relatively faint . Again , when the slit was made to cut the edge of the ignited bead of the earth , the strong green line of erbia was seen to extend to a very small but appreciable distance above or below ( as the case might be ) the continuous spectrum . I could only observe this for the strong line . I failed to get any trace of lines in the spectrum of the flame beyond the incandescent erbia . " The erbia was next heated in the oxyhydrogen flame to the maximum temperature that the wire would bear for three and a half hours , but the green line was seen to be just as strongly marked at the end as at the beginning of the experiment . The bulk of the erbia was so much reduced by this treatment , that I have now scarcely a trace left . " From the results of these experiments , I think we must conclude ( 1 ) that the light emitted by incandescent erbia is derived chiefly from the ignited solid , but that the bright lines observed in its spectrum have as their source a luminous vapour of extremely low tension at even the highest temperature of the oxyhydrogen flame ; ( 2 ) that this interrupted spectrum belongs either to erbium or to its oxide . " If these conclusions are true , it follows that erbia is not an exception to the ordinary law . " It would appear that in these experiments three substances have been employed , varying in their degree of volatility . At the temperature of the oxyhydrogen flame magnesia appears to be less volatile than lime ; but I am in doubt what relative volatility to assign to erbia , since its spectrum of bright lines can be seen when the earth is heated in the plain hydrogen flame , and yet at the much higher temperature of the oxyhydrogen jet the volume of luminous vapour does not appear to materially increase . " Finally , we have yet to learn whether or not in all these cases reduction of the oxide precedes volatilization ; if reduction takes place , the luminous vapour . must be that of the metal . The settlement of this question would no doubt be very difficult . But I rather incline to the view that the vapour whose spectrum is obtained on igniting these earths is that of the metal ; for I find that the bright lines are most easily observed when hydrogen is present in excess in the oxyhydrogen flame . Moreover , the actual amount of matter volatilized . on very prolonged heating is really very

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On the Values of the Integrals\#x222B;\lt;sub\gt;0\lt;/sub\gt;\lt;sup\gt;1\lt;/sup\gt; Q\lt;sub\gt;n\lt;/sub\gt;, Q\lt;sub\gt;n\lt;sup\gt;\#x2032;\lt;/sup\gt;\lt;/sub\gt;, d\#x3BC;, Q\lt;sub\gt;n\lt;/sub\gt;, Qn\lt;sup\gt;\#x2032;\lt;/sup\gt; being Laplace's Coefficients of the Orders n, n\lt;sup\gt;\#x2032;\lt;/sup\gt; with an Application to the Theory of Radiation. [Abstract]

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J. W. Strutt

abs

6.0.4

proceedings

http://corpora.clarin-d.uni-saarland.de/surprisal/6.0.3/?id=112789

http://www.jstor.org/stable/112789

Formulae

Fluid Dynamics

Mathematics

XII . " On the Values of the Integrals Q , Q , , Q , , d , Q , , Q , g , being Laplace 's Coefficients of the Orders n , n ! , with an application to the Theory of Radiation . " By the Hon J. W. STRUTT , Fellow of Trinity College , Cambridge . Communicated by W. SPOTTISWOODE , F.R.S. Received May 17 , 1870 . ( Abstract . ) These integrals present themselves in calculations dealing with arbitrary functions on the surface of a sphere which vary discontinuously in passing from one hemisphere to the other . When n , n ' are both even or both odd , the values of the integrals may be immediately inferred from known theorems in which the integration extends from -1 to + 1 , or over the whole sphere ; otherwise a special method is necessary . In the present paper a function of two variables is investigated , which , when expanded , has for coefficients the quantities in question . As an example of the method , the problem is taken of a uniform conducting sphere exposed to the heat proceeding from a radiant point . It will appear at once that the heat received by any element of the surface is expressed by different analytical functions on the two hemispheres-a source of discontinuity which renders necessary a special treatment of the problem . The solution is afterwards generalized to meet the case of a sphere exposed to any kind of radiation from a distance . One remarkable result not confined to the sphere is , that the effect of a radiation which is expressed by one or more harmonic terms of odd order is altogether nil , with the single exception of the term of the first order .

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Note on the Construction of Thermopiles

553

556

Proceedings of the Royal Society of London

Earl of Rosse

fla

6.0.4

http://dx.doi.org/10.1098/rspl.1869.0097

proceedings

http://corpora.clarin-d.uni-saarland.de/surprisal/6.0.3/?id=112790

10.1098/rspl.1869.0097

http://www.jstor.org/stable/112790

Electricity

Measurement

Electricity

XIII . " Note on the Construction of Thermopiles . " By the EARL or RossE , F.R.S. Received June 14 , 1870 . Although in the measurement of small quantities of radiant heat by means of the thermopile much may be done towards increasing the sensibility of the apparatus by carefully adjusting the galvanometer and rendering the needle as nearly astatic as possible , there must necessarily be some limit to this , and it therefore appears desirable that the principles on which thermopiles of great sensibility can be constructed should also be carefully attended to . With the view of obtaining a pair of thermopiles of greater sensibility and of more equal power than I had been able to procure ready made , I made a few experiments with various forms of that instrument , and I was led to the conclusion ( one which might have been foreseen ) that the sensibility of the thermopile is much increased by reduction of its mass , and more especially by a diminution of the cross section of the elements . To obtain a clear idea of the problem before us , which is , how to construct the thermopile so that , with a given amount of radiant heat falling on its face , the greatest current may be sent through the galvanometer , let us consider the thermopile under two different conditions:1 . With the circuit open . 2 . With the circuit complete . In the first case , when radiant heat falls on the face of the pile , the whole mass of metal rises in temperature , the rise being greatest at the anterior face , and less and less as you approach the other end . This rise of temperature will increase till the heat radiated from the anterior face , together with that which traverses the depth of the pile and is radiated from the posterior face , is just equal to that radiated to the anterior face at that moment , or when 7c ( t +t')= Jt + ( t-t ' ) = Q , where ( t , t ' ) are respectively the temperatures of the anterior and posterior face , s , 1 the cross-section and depth of the pile , c proportional to the mean conductibility of the material of the pile , ( Q ) the quantity of heat falling on the pile in a unit of time , and ( k ) a constant . Let us now suppose the circuit completed , and we shall have , in addition to the above , two causes operating to reduce the temperature of the anterior face , the abstraction of heat by the electric current , and proportional to that current =LI , where I is the intensity of the current and La constant , then there will be equilibrium when c4(t+tt)+LI= t-+ 1 ( t-t)+ LI-Q . It is quite clear therefore that if Q be constant , I will become the larger the smaller the other two terms become ; and therefore as long as the first term continues small compared with the remaining terms , and the resistance in the pile is very small compared with that in the rest of the circuit , we shall increase the intensity of the current by every reduction of the cross-section of the elements of the thermopile . There is another point which , though less important , cannot be entirely lost sight of , namely , that the more we reduce the mass of the anterior face and adjacent parts of the pile , the more rapidly will the temperature rise to its state of equilibrium , and therefore the more convenient will it be for use where the needle is liable to disturbances from various causes , and where consequently the more speedily the needle can be brought to rest , the more accurately will its observed motion be a measure of the radiant heat falling at that moment on the face of the pile . Let us now compare the case of a single pair of small cross-section with a metal disk soldered to the junction of the two bars , and of suffi554 [ June 16 , cient size to catch all the radiant heat required to be measured , with that of a pile of ( n ) pairs , each of equal dimensions with those of the single pair , the area of face being the same in the two cases . By increasing the number of elements from one to n , we increase the number of solderings in that proportion ; consequently the average I1 amount of heat reaching any soldering is n as great as that reaching the soldering of the single pair ; therefore , if the same percentage of the total heat be lost by conduction , the total electromotive force is the same in the two cases . But inasmuch as the total cross-section of metal to conduct the heat away from the anterior face is n times as great in the pile as in the pair , and the resistance of the pile is n times as great as that of the pair , the pile will be inferior in power to the pair , unless these two causes of inferiority are counterbalanced by the loss due to the greater average distance to the soldering from the points where the heat reaches the face , in the case of the pair , than that of the pile of n pairs . The experiments already referred to were made with three different thermoelectric pairs . These consisted each of a pair of bars of bismuth and an alloy of twelve parts of bismuth and one part of tin of different thicknesses , of about equal lengths in each case , and soldered about inch apart upright , on disks of sheet copper of 2 inch diameter . A slip of wood was placed between the two bars , to protect them from injury , and to which they were fixed with thread . The three piles were compared with a pile of four elements , made by Messrs. Elliott , and the deviation due to the latter being taken equal to unity , the following deviations were obtained for the three thermo-pairs : Weight of Weight of Deviation . Metals employed . disk face . two bars . I. 8 grains 42 grains '676 Bismuth , antimony . II . 41 , , 6 , , 1*35 Bism uth tin 12 tin 1JA heavy and a light pile were also compared , taking the interval between raising and depressing the screen , first =2 minute , and then =2 minutes ; and it was found that , in the first case , Deviation due to light pair _= 2 . Deviation due to heavy pair and , in the second case , Deviation due to light pair =29 Deviation due to heavy pair 1870 . ] 55o so that the light pair arrived rather more rapidly at the condition of equilibrium than the heavier pair . Although the above experiments are far less complete than I could have wished , they are sufficient to show that the sensibility of thermopiles may be considerably increased by diminution of the section of the bars composing them ; whether they may be with advantage reduced to a greater extent than I have already done I cannot say , but I am inclined to think that they may . I have ascertained from Messrs. Elliott that the alloys used by them in the construction of thermopiles , at the time when I received mine from them , were 32 parts of bismuth +1 part of antimony , and 14of bismuth +1 part of tin . If allowance be made for the substitution of the first of these two alloys for pure bismuth , the difference between Elliott 's pile and the pairs II . & III . will be rather greater . The pile by Messrs. Elliott , if made of the same metals as I employed , would have been reduced in power from 1 to 0'9 . The construction of thermo-couples , on the plan I have described , is comparatively easy . In about two hours I was able to make one , and in more experienced hands their construction would be still easier . An experiment was made with one of the piles to ascertain whether , when the heat was not directed centrally on the pile , much diminution of power would take place . There was less deviation in consequence of the increase of the mean distance which the heat had to travel before it reached the soldering ; but I believe that this defect might be remedied , probably without diminution of the power of the pile , by increasing the thickness of the face , and leaving the dimensions of the bars the same . 556

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Obituary Notices of Fellows Deceased

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Proceedings of the Royal Society of London

nws

6.0.4

proceedings

http://corpora.clarin-d.uni-saarland.de/surprisal/6.0.3/?id=112791

http://www.jstor.org/stable/112791

Biography

Reporting

Biography

OBITUARY NOTICES OF FELLOWS DECEASED . JEAN VICTOR PONCELET , Foreign Member of the Royal Society , was born at Metz on the 1st of July , 1788 . After having studied Mathematics for two years at the Lycee Imperial of Metz , he was admitted to the & cole Polytechnique , where he remained till 1810 , his studies in the meanwhile having been interrupted by a serious illness . ie then entered the ecole d'Application of Metz as Sublientenant of Engineers , and left it in March 1812 , in order to assist in constructing the defensive works of Ramekens in the island of Walcheren . His first engineering work here was the erection of a casemated fort in a very limited time , on a peat soil , without having at his command proper materials for a foundation . In the month of June 1812 he was called away to take part in the Russian campaign , and joined the invading army at Vitepsk . On the 18th of August he reconnoitred Smolensk , exposed to the fire of the garrison , and afterwards took an active share in the battle fought the same day . On the 19thhe was employed in throwing bridges over the Dnieper below Smolensko , under the fire of the Russian batteries on the opposite bank of the river . Deceiving the enemy by an ostentatious display of preparations for crossing at a particular spot , he succeeded in constructing bridges at other points better protected from the Russian fire . During the retreat from Moscow , at Krasnoi , not far from Smolensko , seven thousand French soldiers under the command of Ney , without artillery , encountered twentyfive thousand Russians with forty-five pieces of artillery , under Prince Miloradowich , on the 18th of November , 1812 . In this battle Poncelet charged the Russian batteries at the head of a column of sappers and miners ; his horse was killed under him , and he was taken prisoner . After a painful four months ' march through snow , half naked and ill fed , in a season when mercury was repeatedly frozen , he arrived at Saratoff on the Volga . In April 1813 , on recovering from an illness brought on by the hardships he had endured , he resolved to occupy his unwelcome leisure with the study of descriptive geometry . But his recollections of the teaching of Monge , Carnot , and Brianchon had been totally effaced by the privations and sufferings he had undergone . Without books to aid him he was obliged , with much labour , to construct bit by bit the elementary propositions required for the line of research he was desirous of following . The results of his labours at this time were afterwards published in Gergonne 's 'Annales , ' from 183 7 to 1821 ; and the original manuscripts , written at Saratoff , were published in 1862 . On the conclusion of peace in June 1814 , he quitted Saratoff for France , where he arrived in September of the same year . From 1815 to 1825 , as Captain of Engineers , he superintended the construction of machinery in the arsenal of Metz . From 1825 to 1835 he was Professor of Mechanics ; and while he imparted to the young officers clear ideas of mechanical science , capable of immediate practical application , he delivered , at the suggestion of Baron Dupin , gratuitous evening lectures on geometry to the artisans of the place , and thereby contributed largely to the establishment of those courses of public lectures that have brought the most fertile results of scientific research within the grasp of the whole nation . In addition to these labours he wrote his 'Traite des Proprietes Projectives des Figures ' ( 1822 ) , 'Cours de Mecanique applique aux Machines ' ( 1826 ) , and many memoirs on Geometry and Applied Mechanics in Gergonne 's and Crelle 's journals . HIe also invented a drawbridge with a variable counterpoise , and an undershot water-wheel with curved buckets , now known throughout Europe by the name of Poncelet 's wheel , which nearly doubles the useful effect of a given water-power . He was promoted to the rank of Chef de Bataillon in 1831 , and became a Member of the Institute in 1834 . From 1835 to 1848 he was on the Committee for constructing the Fortifications of Paris , and was successively appointed Professor of Mechanics at the Sorbonne and at the College de France ; became Lieutenant-Colonel in 1841 , Colonel in 1844 , and General of Brigade on the 19th of April , 1848 . A few days later he was appointed Governor of the Ecole Polytechnique , a post which he held till 1850 . During the troubles of June 1848 , placing himself at the head of the pupils of the Ecole Polytechnique , he led them through the barricades to the Luxembourg , where they formed a guard of honour for the protection of the Provisional Government . For this important service General Cavaignac appointed him to the command of the National Guards of the Department of the Seine . I-e was also elected a Member of the Constituent Assembly . As President of the Scientific Commission sent to the English Exhibition of 1851 , he drew up a Report on the progress of the Arts involving the application of Science during the last half century . Besides the works already mentioned , he wrote a large number of Memoirs and Scientific Reports in the Memorial du Genie , les Avis du Comite des Fortifications , and the Comptes Rendus . He was Grand Officier of the Legion of Honour , Chevalier of the Prussian Order " Pour le Merit , " Corresponding Member of the Academies of Berlin , St. Petersburg , Turin , and of many other learned Societies ; his election as Foreign Member of the Royal Society took place in 1842 . After a long and painful illness , he died in Paris on the 23rd of December , 1867 . NATIANIEL BAGSHAW WARD , F.R.S. , F.L.S. , who died on June 4th 1868 in his 77th year , was a sonnd practical botanist , and was especially known as the inventor of the closely glazed cases for the growth of plants , which bear his name . When quite young he evinced a taste for natural history and made his little collections of plants and animals . A voyage to Jamaica when he was thirteen years old , and the contemplation of the luxuriant vegetable life of that island , inspired him with an ardent love for the science of botany . He was educated to the medical profession , and for many years of his life was engaged in its practice in the east end of London . His leisure time , however , was devoted to the study and cultivation of plants ; and his house in Wellclose Square was conspicuous for the vegetation which surrounded it . But the deleterious atmospheric influences to which it was exposed subjected him to continual vexation and disappointment ; and the only way in which he could maintain a fluctuating appearance of freshness and verdure was by bringing back a renewed supply of plants on the occasion of any visit to nursery grounds or the country . In the summer of 1829 , a solution of his difficulties presented itself . IIe had placed the chrysalis of a moth in some mould in a glass bottle covered with a lid , in order to obtain a perfect specimen of the insect ; after a time a speck or two of vegetation appeared on the surface of the mould , and turned out to be a fern and a grass . His interest was excited ; he placed the bottle in a favourable situation and found that the plants continued to grow and to maintain a healthy appearance . On reflecting upon the matter , he found that the conditions necessary to the life of the plants were maintained , and deleterious agents , as soot , noxious gases , drying winds , &c. , were excluded . The first Wardian case gave rise to numerous others ; and in two or three years the success of the plan was satisfactorily demonstrated . In 1836 Mr. Ward wrote upon the subject to the late Sir W. Hooker ; and the letter was published in the Companion to the Botanical Magazine for May of that year . In 1838 Mr. Faraday lectured upon the " cases " at the Royal Institution ; and subsequently Mr. Ward himself explained his plan at various Societies and at Meetings of the British Association . In 1842 the first edition of Mr. Ward 's work on " The Growth of Plants in Closely-glazed Cases " was published ; and a second edition appeared a few years later . It was soon recognized that Mr. Ward 's method was susceptible of various valuable applications , of which the following maybe noticed:--I . The growth of plants in the dwellings of all classes , in town as well as country . 2 . The transport of plants to and from different countries : the tea-plant and the cinchona-tree have by means of the Wardian cases become established in India . 3 . For purposes of philosophical investigation . 4 . To the study and conservation of animals : the Vivaria were first established as a modification of the cases by Mr. Ward himself . When residing at Wellclose Square , Mr. Ward gave frequent microscopical soirees . Out of these sprang the Microscopical Society in 1840 , Dr. Bowerbank and the late Messrs. Quekett and Jackson having also taken part in its foundation . Hle was elected a Fellow of the Royal Society in 1852 . In 1856 , a large number of friends combined to recognize Mr. Ward 's services by having his portrait painted by J. P. Knight , R.A. , and placed in the meeting-room of the Linnean Society . The estimation in which the subject of this notice and his scientific services were held by those best capable of forming an opinion , will be shown by the following extracts from a letter written by Dr. Hooker to the editors of a scientific journal:"During the whole period that I knew Mr. Ward , and , I believe , for a many years before , his hospitable house , first in Wellclose Square , and afterwards at Clapham Rise , was the most frequented metropolitan resort of naturalists from all quarters of the globe of any since Sir Joseph Banks 's day . His unpretending entertainments were frequent , for many years periodic , and often weekly . On these occasions his many scientific friends flocked to see himself , his live plants , and the many specimens , instruments , and preparations he had collected to instruct and entertain them ; and on such occasions it was that many a country and colonial naturalist was introduced for the first , and too often for the last time in his life , to some of the most eminent naturalists in Europe . " Of the value of that contrivance which justly bears his name , the Ward 's case , it is impossible to speak too strongly ; and I feel safe in saying that without its aid a large proportion of the most valuable economic and other tropical plants , now cultivated in England , would not yet have been introduced . " " Of even more consequence was the application of these cases to town gardening , whereby he has afforded to the denizens of this metropolis far greater and purer pleasures than all artists , house-decorators , &c. have contributed ; for a primrose placed in flower under a bell-glass at Christmas in a London drawing-room will charm when a Raphael does not , and will charm none the less when a Raphael charms also . " " In the memory of all who knew him , Mr. Ward will live as a type of a genial , upright , and most amiable man , an accomplished practitioner , and an enthuiastic lover of nature in all its aspects . " MR. ROBERT PORRETT was born on the 22nd September 1783 . His father held the office of Ordnance Storekeeper in the Tower , and resided there ; and the son , having early shown an aptitude for such a situation , was employed as his father 's assistant , and , succeeding him in his appointment , eventually rose to be chief of the department . His official work , not being of an engrossing nature , left him leisure to apply his intelligent and inquiring mind to scientific pursuits , especially to chemistry ; and inasmuch as he received a medal from the Society of Arts for a chemical discovery in 1809 , he was probably at the time of his death the oldest representative of experimental chemistry in this country . In fact he was a worker in chemistry before the introduction of the atomic theory , and was among the first to apply the new doctrine to the verification of chemical analysis . Mr. Porrett 's earliest researches were on hydro-ferrocyanic and hydrosulphocyanic acids , of which he was the discoverer . The investigation of the constitution of these acids ( which he named ferruretted and sulphuretted chyazic acids ) and of their salts forms the subject of various papers which he contributed between 1809 and 1819 to the ' Philosophical Transactions ' and other scientific publications : they are as follows:-"On Prussic and Prussous Acid , " Trans. of the Soc. of Arts , vol. xxvii . 1809 , p. 89 ; " On the Nature of the Salts termed triple Prussiates , " &c. , Phil. Trans. 1814 , p. 527 ; " Further Analytical Experiments relative to the Constitution of the Prussic , of the Ferruretted Chyazic , and of the Sulphuretted Chyazic Acids , and on that of their Salts ; together with the application of the Atomic theory to the analysis of these Bodies , " Phil. Trans. , 1815 , p. 220 ; " On the Anthrazothion of Von Grotthus , and on Sulphuretted Chyazic Acid , " Thomson 's Annals of Philosophy , vol. xiii . ( 1819 ) p. 356 ; " On the Triple Prussiate of Potash , " Ann. Phil. vol. xii . p. 214 , which contains a discussion of his own analyses of " ' ferruretted chyazic acid , " and that of Dr. Thomson , published in a previous part of the same volume ; " On Ferrochyazate of Potash , and on the Atomic weight of Iron , " Ann. Phil. vol. xiv . 1820 , p. 205 . In 1813 Mr. Porrett was engaged with Messrs. Wilson and Rupert Kirk in an investigation of chloride of nitrogen , with a view chiefly to the examination of the physical properties and chemical composition of that dangerously explosive compound , and the discovery of safe and suitable processes for preparing it . In 1816 he communicated to Thomson 's Annals of Philosophy , vol. viii . p. 74 , an account of " Two Curious Galvanic Experiments , " in which he showed that a fluid is made to pass against gravity by the electric current through a membrane from the positive to the negative pole when the conducting wires of a battery are connected with water placed at different levels on each side of the membrane . The fact so discovered by him is by German writers generally associated with his name as " das Porrettsche Phanomen . " He also described the increase of action which is produced in an exhausted voltaic battery by removing a portion of the fluid , whereby the still moist plates are exposed to the action of the air . In 1817 he made some " Observations on the Flame of a Candle , " which were published in the 'Annals of Philosophy , ' vol. ix . p. 337 . After an interval of twenty-six years , he again , in 1846 , at the age of sixty-three , took up chemical investigation , and contributed , in conjunction with the late E. F. Teschemacher , a paper " On the Chemical Composition of Gun Cotton " ( Memoirs of the Chemical Society , vol viii . 1845-1848 , p. 258 ) . His last paper " On the existence of a new Vegeto-Alkali in Gun Cotton , " for which he proposed the name of Lignia , was read before the Chemical Society on December 21st of the same year , and is printed in the Memoirs , vol. iii . p. 287 . While devoting his leisure time principally to chemistry , Mr. Porrett also occupied himself with antiquarian pursuits , especially the study of ancient arms and armour , for which his residence in the Tower afforded favourable opportunity . He retired from official duty in 1850 , after a service of 55 years . On that occasion his long and useful service was honourably recognized by his superiors , and he received most gratifying expressions of regard and attachment from his subordinate officers . He was a Fellow of the Astronomical and Antiquarian Societies , and one of the original members of the Chemical Society ; his election into the Royal Society was in 1848 . He died on the 25th November 1868 , at the age of 85 . CARL FRIEDRICH PHILIPP VON MARTIUS , Foreign Member of the Royal Society , was born on the 17th of April , 1794 , at Erlangen , where his father , Ernst Wilhelm Martius , was Court Apothecary , and Ionorary Professor of Pharmacy in the University . The family is said to have come from Italy , but had for several generations been settled in Germany . After a careful and judicious training at home , for which he was indebted chiefly to an intelligent and accomplished mother , young Martius received his general education in the school and the gymnasium of his native town . From his father he had inherited a taste for Natural History ; and under the tuition of Professors Richter and Besenbeck , of the Gymnasium , he acquired a well-grounded knowledge of classical literature ; so that a good foundation was laid for that well-balanced general mental culture of which the fruits are conspicuous in his writings . When not quite sixteen years of age , he entered the University of Erlangen . His main object was the study of medicine , but he also followed his early bent towards Natural History , and especially Botany . The Botanical Professor of that day was Schreber , who had himself studied under Linneus ; but Martius 's attachment to the science was greatly fostered and promoted by the friendship of the brothers Nees von Esenbeck , then his fellow students , who afterwards rose to eminence as botanists . From the elder of the brothers Martius also received a tincture of the then prevalent " ' Natur-Philosophie , " which may be perceived to colour his earlier writings ; but its influence seems to have been but transient . In March 1814 he was promoted with distinction to the degree of Doctor of Medicine , and published his inaugural dissertation under the title " Plantarum Horti Academici Erlangensis Enumeratio , " a critical catalogue of plants arranged according to the Linnean system . An event had happened some time before which decided Martins 's future career . The Academy of Sciences of Munich , on the death of Schreber , sent to Erlangen two of its members , Schrank and Spix , to acquire his botanical collections for the Academy ; and these naturalists , having seen the promise of future excellence evinced by the young man , invited Martius to apply for admission into the " Institution of Eleves , " then existing in the Academy , in which the pupils had the advantage of following out the higher study of selected branches of science under the auspices of the Academy and the immediate guidance of certain of its members . Through the prospect thus set before him , the wish which Martius had already entertained of devoting himself entirely to botany , became a settled resolution . After going through the prescribed trials , he was in May 1814 received among the Eleves of the Academy , and appointed , under the direction of Schrank , now advanced in years , to be assistant in the management of the Botanic Garden at Munich , with an annual salary of 500 florins . Two years later he was advanced to the rank of " Adjunct of the Academy , " an order which no longer exists , having been abolished , together with the Institute of Eleves , by King Louis in 1827 . Martius not only laboured zealously in the superintendence of the Garden , but made frequent excursions through Bavaria and the adjacent regions for the study of the indigenous flora ; and it was on one of these occasions that he made the friendship of Hoppe , the Director of the Botanic Garden of Ratisbon , and began with him a scientific correspondence which was longenduring . At this time he published the 'Flora Cryptogamica Erlangensis ' ( Norimbergi , 1817 ) , which contained the results of his first independent researches , and met with high approval from his fellow workers in the science . His earnest devotion to study , his conspicuous talents , and his untiring activity , could scarcely fail to earn for him the regard of his older academical colleagues , such as Schrank , Schlichtigroll , Scenmmerring , and the Conservator General von Moll-all of them men fitted to produce a beneficial influence on his mental development . In like manner he attracted the kindly notice and favourable consideration of the King Maximilian Joseph I. , who , being a great lover of plants , paid frequent visits to the Garden under the welcome guidance of the young superintendent ; and this had an important effect on his future fortune . This enlightened prince had for some time entertained the project of sending a scientific expedition to America ; and as the Emperor of Austria was about to send out scientific explorers to Brazil in the retinue of the Archduchess Leopoldina , who was about to sail for that country as the bride of the Crown Prince of Portugal , afterwards the Emperor Don Pedro I. of Brazil , King Max. Joseph availed himself of the opportunity offered to him of sending out two Bavarian naturalists on that occasion . The choice fell on Spix as Zoologist , and Martius as Botanist , who was selected by the king himself . After but a brief time allowed for equipment , the two travellers sailed from Trieste on the 2nd of April , 1817 , with the imperial cortege , and , after touching at Malta , Gibraltar , and Madeira , arrived at Rio Janeiro on the 15th of July . There they parted from the Austrian savans , and set out on their own journey . It is unnecessary here to trace the course of their travels ; suffice it to say that , after traversing the vast territory of Brazil in various directions , and ascending the River Amazons and its tributary the Hyapura as far as the confines of Peru and New Granada , they arrived at Para on their return journey on the 16th of April , 1820 , three years after they had sailed from Europe . From Para they were conveyed to Lisbon in a Portuguese ship of war , and reached Munich on the 8th of December , 1820 . This expedition , irrespective of the sea voyage , extended over nearly 1400 geographical miles , and for months led through the most inhospitable and dangerous regions of the New World . Both explorers , however , escaped without any important disaster on the road , and they had the rare good fortune to preserve and bring home their collections complete and un injured . The material fruits of the expedition consisted of about 6500 species of plants , the majority dried ; but several living species , as well as seeds , were also brought home . The zoological collections ( to which Martius contributed also on his solitary voyage up the Iyapura ) numbered 85 species of Mammals , 130 of Amphibia , 350 of Birds , 1 16 of Fishes , 2700 of Insects , 80 of Arachnoids , and 80 of Crustacea . The species , especially the plants , are represented , many by numerous , and all by well-preserved specimens . On their return home , the king nominated the travellers Knights of the Order for Civil Merit ; and Martius received the appointment of ordinary member of the Academy of Sciences , and second conservator of the Botanic Garden . In consequence of this expedition , the direction of Martius 's future scientific activity was decided . Brazil was thenceforward the country to which he devoted the greater part of it . Before everything else his energy was centred on the flora of Brazil . The first work made public relative to the Brazilian expedition was the Narrative of the Journey . It appeared in 1823-31 , in three quarto volumes , accompanied by an atlas . The compilation of this work was originally entrusted conjointly to both travellers by Maximilian Joseph I. ; but Spix did not long survive the completion of the first volume , and so it happened that by far the greater portion of the work proceeded from Martius 's unaided pen . Of course in the ' Narrative of Travels ' natural products are treated of more or less in detail ; but it could not be occupied with the special discussion and elaboration of scientific matter . This was reserved for a separate work , which appeared contemporaneously in a magnificent series of volumes . In the first place Martius undertook only the botanical section , and Spix the zoological ; but , on account of the death of the latter in 1826 , when he had only worked up the mammals , the birds , and a part of the amphibia , the continuation of this part of the work also fell upon Martius . He acquitted himself of the task in the most satisfactory manner , having secured the assistance of Agassiz , Andreas Wagner , and Pertz , for the actual work , whilst he acted as editor . The publication of the botanical treasures took the form of a selection of the most interesting novelties . The Phanerogamia , or flowering plants , were illustrated in the 'Nova Genera et Species PlantarumBrasiliensium ' ( 3 vols.fol . , Munich , 1823-32 ) , and the Cryptogamia in the 'Icones Selectee Plantarum Cryptogamicarum Brasiliensium , ' 1 vol. , 1827 ) . The first volume of the former work was prepared by Martius 's colleague , Zuccarini , the remainder entirely by Martius , except the chapter in the 'Icones Selectee ' on the internal structure of Tree-Fern stems , from the pen of Hugo von Mohl-a chapter that served to enhance the value of the work in the highest degree . In these publications not only were many new and highly remarkable plants made known ( more than 400 species and more than 70 genera ) , but they were also so fully and lucidly described that botany received an essential enrichment . A practised and quick sight for natural affinities , a happy gift of combination-in short , an essentially " systematic tact , " placed Martius in the rank of the first botanists of his time . A third work was taken in hand by Martius in 1823 , and , indeed , the one with which his name will be most closely and enduringly connected . This was the Monograph of Palms , ' Historia Naturalis Palmarum ' ( 3 vols . imp . fol. , Munich , 1823-50 ) . The peculiar richness of Brazil in Palms , the beauty of Brazilian forms , and the honour likely to accrue from a new and comprehensive work on this group of plants induced Martius to concentrate his attention upon them immediately after his arrival in Brazil . The fulfilment of this great undertaking cost twenty-eight years of labour and research . For the matters with which he was less conversant , Martius obtained the cooperation of distinguished colleagues . The chapter on the anatomy of palms was written by H. von Mohl ; the fossil palms fell to the share of F. Unger ; and Sendtner and A. Braun contributed to the morphology . But by far the greater part came from the pen of Martius himself , notably : the chapter on the geographical distribution of palms , in which Martins enunciated his views on phyto-geography in general ; and the whole of the third volume , containing descriptions of all known palms , systematically arranged , and forming in itself an almost complete monograph of the family . The scientific merit of this work was universally acknowledged . Not only was the ? special knowledge of palms thereby greatly extended , but the science of botany in general was signally promoted ; and it may be said , in the words of a great naturalist , that , " so long as palms are known and palms are grown , the name of Martius will not be forgotten . " The last great work by Martius to which we can refer on this occasion is the ' Flora Brasiliensis . ' He had made an attempt , in conjunction with Nees von Esenbeck , to publish such a work on a small scale , but soon abandoned the idea ; but in 1839 , encouraged by Prince Metternich , he planned a far more ambitious publication , in conjunction with the celebrated Viennese botanist Endlicher . The groundwork of it was to consist of an entirely new and scientific elaboration of all the accessible materials brought together from Brazil , accompanied by numerous plates , thus forming a splendid systematic whole . To comprehend in some degree the magnitude of such an undertaking , it must be remembered that the flora of Brazil numbers almost five times as many species as that of the entire area of Central Europe . It was plain that the carrying out such a work could be accomplished only by the joint labours of many scientific men ; and Martins was fortunate enough to obtain the services of the most eminent German and foreign botanists for this purpose . The Emperor Ferdinand I. of Austria , and the Emperor Don Pedro II . of Brazil , and also King Louis of Bavaria took the work under their special patronage . After Endlicher 's death in 1849 , Fenzl , his successor in office , supplied his place , as co-editor with Martius . At first the work proceeded slowly , on account of the novelty and costliness of the undertaking ; but since the year 1850 , in consequence of the increased interest taken in it by the Brazilian Government , it has gone on more rapidly , and has now reached the 46th part . The completion , which Martins so longed to see , has been entrusted to his friend Dr. Eichler . It was one of Martius 's last cares to take the needful steps to ensure its continuance ; so that we may reasonably hope to see this noble monument of German industry in science brought to a close . Even now the parts that have appeared form the most comprehensive work in botanical literature yet published . Nearly 10,000 species are described , and these are illustrated by more than 1100 folio plates . It is evident that the editing and publication alone of so enormous a mass of matter is a performance worthy of the highest acknowledgment ; but Martius 's merit was by no means limited to that . True , of all the monographs published , two only were by Martius ; but then he supplemented nearly all the others by valuable explanations on the geographical distribution and the medicinal , technical , and economical importance of the several plants . He also contributed a series of characteristic plates representing the vegetation ( 'Tabulae Physiognomicse ' ) , accompanied by masterly definitions , in elegant Latin . He also contributed maps of the floral districts , routes of travel , &c. Several of the monographs in the 'Flora Brasiliensis ' are esteemed as masterpieces ; for in many cases the men who wrote them had previously devoted years of study to the respective groups . The mere enumeration of Martius 's other writings would fill a long space , for there are more than 150 separate works . Among these may be specially mentioned his 'Beitrage sir Ethnographie und Sprachkunde Braziliens ' as evidence , besides what appears in the narrative of his travels , that he devoted himself to other objects in Brazil besides the study of its natural history . Reverting to the main facts of Martius 's life , we left him in 1820 , just after his return from Brazil , when he was nominated ordinary member of the Academy , and second conservator of the Botanic Garden . For some years his position remained unchanged . When , however , in 1826 , King Ludwig I. ascended the throne , and the University of Landshut was removed to Munich , he was appointed Professor of Botany in that institution ; and six years later , upon the retirement of the aged Schrank , he received the post of first conservator . With the exception of occasional journeys to England , France , Holland , &c. , he discharged almost uninterruptedly the duties of both appointments until 1854 . In 1840 he was elected Secretary to the Mvathematical and Physical Class of the Munich Academy , and continued in the office till the time of his death . With a budget of only 4500 florins , Martius succeeded , with the assistance of the highly meritorious gardener Weinkauff , in making the Botanic Garden a model establishment . The Garden had just been rearranged with great care , and partially replanted , when in 1854 , by the erection of a glass building for an industrial exhibition , the beautiful plan was marred . Martius , who had vainly remonstrated against this intrusion , ceased to interest himself in the garden ; and his principal occupation thereafter was the publication of the ' Flora Brasiliensis . ' Whatever the world could offer in acknowledgment of his merits Martius received . He was elected member of nearly all the academies and learned bodies in , Europe , and kings and emperors honoured him with the most distinguishing marks of favour . His election as Foreign Member of the Royal Society was in 1838 . He rejoiced in the esteem and friendship of his most distinguished contemporaries ; and plants and animals , and even a mountain ( Mount Martius in New Zealand ) , were named in his honour . But the most gratifying expression of homage and veneration was presented to him on the 30th of March , 1864 , the 50th and jubilee anniversary of the day on which he was invested with the degree of Doctor . His friends caused a medal to be struck , with the inscription , " Palmarum patri dant lustra decem tibi palmam . In Palmis resurges . " And on the 15th of December , 1868 , the remains of the departed were lowered into their last resting-place bedecked with Palm-leaves . GE , NERAL THOMAS PERRONET THOMPSON was born at Hull , on the 15th of March , 1783 , the eldest of three sons of Thomas Thompson , Esq. , a merchant and banker of that town , and for several years M.P. for Midhurst . His mother was the grand-daughter of the Rev. Vincent Perronet , vicar of Shoreham in Kent , a Swiss Protestant by descent , and one of the few clergymen of the Church of England who joined John Wesley at the commencement of his mission . The youth 's early education was received at the Hull grammar school , under the Rev. Joseph Milner , author of the " Ecclesiastical History ; " and in October 1798 he entered Queen 's College , Cambridge , where in due time he took his B , A. degree with the honour of Seventh Wrangler-no bad start in life for a boy under nineteen . In 1803 he sailed as a midshipman in the 'Isis ' of 50 guns , the flagship of Vice-Admiral ( afterwards Lord ) Gambier , on the Newfoundland station , and was shortly after put in charge of a West-Indiaman recaptured in the mouth of the Channel , and ordered with other prizes to Newfoundland , where she arrived , the only one that had stuck by her convoy through those foggy latitudes . In the following year he received information of having been elected to a Fellowship at Queen 's , " a sort of promotion , " he remarks , " which has not often gone along with the rank and dignity of a ? midshipman . " Trafalgar , for which he saw Nelson embark on board the 'Victory ' at Portsmouth in September 1805 , closed the prospect of active service in the navy , and in 1806 he joined the " old 95th Rifles " as a second Lieutenant , and was among the prisoners captured , together with General Crawford , by the Spaniards in the Convent of San Domingo , in Whitelock 's attack on Buenos Airs , on the 5th July , 1807 . After his liberation and return to England he was sent in the spring of 1808 , at the age of twenty-five , as Governor , to Sierra Leon , through the influence of Mr. Wilberforce , an early friend of his father 's . Here his efforts to put down the Slave Trade , which secretly existed under the name of " apprenticeship , " marked the man who ever after stuck " closer than a brother " to the dark-skinned races of the earth . " There was no time for hesitation " ( he wrote long afterwards ) . " Of two things he must do one , either withdraw under the pressure of the acknowledged danger of meddling with a dishonest system , or push forward for the present abatement of the mischief , with the almost certainty of being abandoned by the government at home . " He chose the latter , and was recalled . When the official documents connected with his proceedings were subsequently required for discussion in Parliament , reply was made that they could not befound . After marrying , in 1811 , Anne Elizabeth , daughter of the Rev. Thomas Barker , of York , he joined the 14th Light Dragoons in Spain as Lieutenant , and was present at the actions of Nivelle , Nive , Orthes , and Toulouse , for which he received the Peninsular War-medal with four clasps . During the campaign of 1814 he was taken off regimental duty and attached to the staff of General ( afterwards Sir Henry ) Fane , of whose kindness and ability be preserved a grateful recollection . " Some old dragoons , discharged on eightpence a day , " he writes of himself , " may remember that he was a careful leader of a patrol , a good look-out on picquet , could feel a retiring enemy , and carry off a sentry for proof , as well as another , a great hater of punishment , and a man of very small baggage , consisting of something like a spare shirt and an Arabic grammar . " His youngest brother , Charles , B.A. and Travelling Bachelor of Queen 's , and Lieutenant and Captain in the 1st Foot Guards , was killed in action at Biarritz , in the South of France , on the 12th December , 1813 ; and the survivor , in the irresistible desire of seeing his face once more , had him taken up a few days after and reinterred in the garden of the Mayor of Biarritz , where he rests among the strawberry beds with two other officers of the same regiment , -over whose graves the gallant Frenchman has placed a stone with an appropriate French inscription . This striking incident was commemorated by the muse of Amelia Opie , who on this occasion felt as a friend , a relative , and a poet . Promoted at the peace of 1814 , Captain Thompson exchanged into the 17th Light Dragoons , serving in India , where he improved his knowledge of Arabic , which he had begun to study as a subaltern of dragoons in Spain . Arriving at Bombay in 1815 , he soon after served in the Pindarry campaign , and had charge of the outposts of the force under Sir William Grant Keir , whom he accompanied in 1819 as Arabic interpreter to the expedition against the Wahabees of the Persian Gulf . In this capacity he assisted at the reduction of Ras al Khyma and other places on the coast , and had a prominent part in negotiating the treaty with the defeated tribes , the most remarkable article in which was the declaring the Slave Trade to be piracy ; the earliest declaration to that effect in point of time , though the American one reached England first ( see " Exercises , " vol. iv . p. 29 ) . When the main body of the expedition returned to Bombay , he was left in charge of Ras al Khyma with 1100 men , Sepoys with a detachment of European artillery , and was eventually ordered to demolish the town , and withdraw the troops to the island of Kishme on the Persian coast . A misunderstanding having arisen between the Bombay Government and the Arabs of Al Ashkerch on the coast of Oman , who had plundered certain boats , the former sent an order to Captain Thompson to act against them from Kishme in the event of their clearly appearing to be piratical , but to address a letter to them previously to any attack being made . This attempt at negotiation failing through the murder by the hostile tribe of the messenger bearing the letter , the injunction to communicate appeared to be fulfilled and answered . Few will see any alternative but to execute the orders to act ; and military men will comprehend the duty of acting with decision under the circumstances which had arisen . Landing at Soor , on 4he Arabian coast , forty-six English miles from the town of the hostile tribe of Beni Bou Ali , Captain Thompson 's small force of 320 Sepoys and four guns was joined by the Imam of Maskat with 2000 men of his own . The force of the enemy was reported to be 900 bearing arms . On the 9th November , 1820 , as the column was toiling through the sand , the hostile sheik , Mohammed Ben Ali , advanced to the attack , sword in hand . What followed is best described in Captain Thompson 's own words , written in a private letter the next day:- " The Arabs made the guns the point of attack , and advanced upon them . The instant I heard a shot from the light troops , which showed the Arabs to be in motion , I ordered the Sepoys to charge with the bayonet . Not a man moved forward . I then ordered them to fire . They began a straggling and ineffectual fire , aided by the artillery , the Arabs all the while advancing , brandishing their swords . The Sepoys stood till the Arabs were within fifteen yards , when they turned and ran . I immediately galloped to the point where the Sepoys were least confused , and endeavoured to make them stand ; but they fired their musquets in the air and went off . The Imam 's army began a fire of matchlocks , and went off as soon as the Arabs approached . I rode to the Imam and found him wounded . The people just ran like sheep . I saw some of the European artillerymen , and ran to endeavour to make them stand ; but they were too few to do anything . " In the midst of the megle the writer was struck on the shoulder by a matchlock ball , which passed through coat and shirt , grazing the skin , as he used to say , " like the cut of a whip . " The loss of the force in men and guns was most severe , " as must always be the case , " he observes , " when troops wait to be attacked with the sword and then give way . " The remnants were at length rallied at the town of Beni Bou Hassan , about three miles from the scene of action , and after repulsing a night attack , were led back overland to Maskat by Captain Thompson in person , eight days after the fight . Another expedition was quickly sent from Bombay . The town was taken , and the defenders were conveyed as prisoners to Bombay , where , at the meeting between the captive sheik and his original assailant , they agreed heartily on one point , that it would have been a happy thing for both if the letter , lost by the murder of the messenger , had reached its destination . A court-martial followed , as usually happens in cases of disaster , however undeserved . he was 'honourably acquitted " of the two graver charges affecting his personal conduct , and only " found guilty " of so much of the remainder as , in the opinion of the Court , warranted a reprimand for " rashly undertaking the expedition with so small a detachment , " and for " having addressed an Official Report to Government , in which , from erroneous conclusions , he unjustly and without foundation ascribed his defeat to the misbehaviour before the enemy of the officers and men under his command . " The Report alluded to is in the Supplement to the ' London Gazette ' of the 15th and 18th May , 1821 ( copied in the 'Times ' of the 19th ) , and may be usefully compared with the finding of the Court . Their position no doubt was painful , as standing between the incensed Bombay Government and its unsuccessful officer ; and it was difficult to reconcile the logic of facts with a natural regard for the wounded feelings of the Company 's service . The wars of Affghanistan , Sind , the Punjab , and the Mutiny had not taken place to prove the inferiority of Sepoys to a hardier race ; and Indian public opinion was slow to believe anything to their disadvantage . Under these circumstances , and viewed by the light of subsequent experience , the result of the trial was alike honourable to the Court and to the accused ; but it nearly broke his heart at the time , and left traces for life on his mind and spirits . Yet it is characteristic of his generous disposition that he retained no prejudice against the Sepoys as a body ; and when they were punished , as he thought , with undue severity after the mutiny , his voice and pen were vigorously exerted in their behalf . In 1822 , his regiment being ordered home , Captain Thompson returned with his wife and child by the Red Sea , Cosseir , Thebes , the Nile , Cairo , and Alexandria , through Italy and France . The " overland route " of that day was a very different undertaking from what it is now ; and the voyage , performed in country vessels , was protracted by contrary winds , so that more than a year was consumed in reaching England . In 1827 he was promoted to a Majority in the 65th Regiment , then in Ireland , and in 1829 to an unattached Lieutenant-Colonelcy of Infantry . His subsequent promotions bore date , Colonel 1846 , Major-General 1854 , Lieutenant-General 1860 , and General 1868 . And now , after his return to England , commenced the literary and political portion of his life . To the first number of the 'Westminster Review ' he furnished the article on the " Instrument of Exchange , " the result of eleven years ' continuous study . In 1829 he became virtually the sole proprietor ; and beginning with the article in support of Catholic Emancipation , of which 40,000 copies were dispersed under the title of the " Catholic State Waggon , " he continued to write at the rate of three or four articles per number , making upwards of a hundred in all , till the Review was transferred in 1836 . In 1825 he wrote , to serve the Greek cause , two pamphlets in modern Greek and French on the service of outposts , and on a system of telegraphing for field service . In the following year he published the 'True Theory of Rent , ' in support of Adam Smith against Ricardo and others ; in which view he was borne out by Say . And in 1827 , eleven years before the Anti-Corn Law League was formed , and when he was only a Major in a marching regiment , he published his celebrated ' Catechism on the Corn Laws , ' a work which went through many editions , and to which Mr. Cobden always acknowledged the obligations of the Free Trade cause . " For breadth of principle , " says a generous political opponent , " humorous and telling illustration , a strong racy Saxon style , there is nothing in Cobbett superior to this little pamphlet . " He was elected a Fellow of the Royal Society in 1828 . The following year he wrote " Instructions to my Daughter for Playing on the Enharmonic Guitar ; being an attempt to effect the execution of correct harmony , on principles analogous to those of the ancient Enharmonic . " He followed this up by the construction on the same principle of an Enharmonic Organ , which was shown at the Great Exhibition of 1851 , and " honourably mentioned " in the Reports of the Juries . In 1830 he published 'Geometry without Axioms , ' being an endeavour to get rid of Axioms , and particularly to establish the Theory of Parallel Lines without recourse to any principle not founded on previous demonstration . The work went through several editions , with successive amendments , but attracted more attention in France than here ; and an accurate translation was published by M. Van Tenac , Professor of Mathematics at the Royal Establishment at Rochefort , and subsequently attached to the Ministry of Marine at Paris . In 1830 he also published a pamphlet on the 'Adjustment of the House of Peers , ' which obtained the remarkable compliment of being republished in Cobbett 's Register . The same year , at the invitation of Jeremy Bentham , he edited the Tenth Chapter ( on military establishments ) of his " Constitutional Code , " and wrote the notes and " ' Subsidiary Observations " at the end . In 1834 he published at Paris , in answer to the Enqudte , or Commercial Inquiry then carried on by the French Government , the " Contre-Enquete ; par l'Homme aux Quarante Ecus ; " in which the principles of commercial freedom were developed under a familiar form . In 1842 he collected all his writings in six closely printed volumes , under the title of " Exercises , Political , and others , " -a mine of literary , political , military , mathematical , and musical information . This was followed , in 1848 , by his ' Catechism on the Currency , ' the object of which is to show that the best currency is one of paper , inconvertible , but limited . The views set forth in this publication are embodied in a motion of which Colonel Thompson gave notice in the House of Commons on the 17th July , 1850 , and in a series of twenty-one Resolutions which he moved in the House on the 17th June , 1852 , and which were negatived . ( 3 Hansard , cxxii . 899 ) . His 'Fallacies against the Ballot , ' afterwards reprinted as a " Catechism , " first appeared in 1855 . At the general election in January 1835 , he polled 138 6 votes at Preston without being present . In June following he was elected , after a sharp contest , by a majority of five , for Hull , his native place , and was , as he expressed it , " laid down and robbed at the door of the House of Commons " to the amount of ? 4000 by a petition of which none of the charges were proved before the Committee . While in Parliament , both at that time and afterwards , he maintained a constant correspondence with his constituents , addressing them generally twice a week through local newspapers in short and pithy reports , which were republished under the title of " Letters of a Representative , " and " Audi Alteram Partem , " this last consisting chiefly of an indignant commentary on the measures taken to suppress the Indian Mutiny . He was also an active promoter of the abolition of corporal punishment in the army , and an opponent of the restriction of marriage with a deceased wife 's sister . Defeated at Maidstone by Mr. Disraeli in 1837 , and subsequently at Marylebone , Manchester , and Sunderland , he was elected in 1847 for Bradford , again defeated there in 1852 by six votes , and finally , in 1857 , returned without a contest . The dissolution of 1859 closed his career in Parliament , for which he never stood again , although he continued to write in various periodicals on public matters under the signature of " An Old Reformer , " and latterly as " A Quondam M.P. , " in strenuous defence of the Irish Church . As one of the leaders of the Anti-Corn Law League , the pioneer and fellow-labourer of Cobden and Bright , he will live in the grateful remembrance of many whose cheap loaf is due to the Father of Free Trade , " the literary soldier who wrote the 'Corn Law Catechism . ' " In person he was short , active , and well made , and in middle age might be , as he described himself , " stouter than would become a Light Dragoon ; " but he was capable of much fatigue , and insensible to irregularities of hours and seasons . Of his acquirements and ability the foregoing sketch may give some idea ; but only those who knew and loved him in private life can tell the depth of his learning , of his goodness , benevolence , and kindness of heart . After a life so long , so varied , and at times so stormy , his end came peacefully at Blackheath , early on the 6th of September , 1869 , in the 87th year of his age . He had written letters on various subjects , including his favourite Enharmonic Organ , up to the middle of the day before , in full possession of his mental and bodily faculties , and he may be said to have died , as he lived , pen in hand--"Qualis ab incepto . " He was followed by his children and grandchildren to Kensal Green , where he rests not far from an old friend and fellow reformer , Joseph Hume . In the list of Fellows lost to the Royal Society this year , the name THoMAs GRAHAM stands out with great prominence . Much as he was known , and widely , he was little seen in what may be called the social circles of scientific life ; and although we shall miss him and his work in a field which he alone seemed to cultivate and understand , and although his work must greatly influence science , and through it civilization , the public will not observe that any name of importance is absent on great occasions or in large meetings . He was born in Glasgow , in 1805 , Dec. 21st . His father was a merchant of that city , and gave him every opportunity of learning . Having attended the primary school , he went at nine years of age to the Grammar School for Latin and Greek under Dymock , for the usual term of four years , and under the rector , Dr. Crystal , for the finishing year . Then he went to the University , at an early age certainly , but such is the custom of the place . We hear of no great feats of scholarship in the Grammar School . Graham was too quiet to be brilliant . We hear of diligence , and that he occupied a seat in the first form , and got prizes for lessons as well as a prize every year for not having been absent for one day . The education at this school was sound , and it was not easy for a boy to leave it without some useful knowledge of the languages taught , as well as a very clear idea of the history and progress of the world . In college he remained for seven years before taking his degree of M.A. in 1826 . At that time the university was too much of a high school , but it was of course obliged to suit itself to the young who attended . It is clear that Graham had his whole time occupied at the best schools of learning around him , and many must still remember his teacher in chemistry , Dr. Thomas Thomson , and in physics , Professor Meikleham . -Iis attention seems to have at this time been devoted for the most part to physics and mathematics . When he had taken his degree , he was expected to enter on distinct professional studies . His father had designed him for the church , but his mind was bent on the study of science . A struggle took place between two strong wills , and caused him much misery for many years . Neither was accustomed to speak his mind , otherwise the great respect which each had for the other would have been discovered sooner for the good of both . This sorrow was softened to Graham by the great tenderness of his mother , to whom he was most devoted , and to whom he told , in a long series of confiding letters from Edinburgh , where he now went to study , all his doings and feelings . In these letters we are led to hope for a very full picture of the early manhood of Graham . It was at this time that he learnt isolation , and satisfied his love of sympathy by writing , so that he acquired a habit which never left him . It is in these notes , reaching up to his last illness , that we must look for all that he thought on scientific and other subjects ; and they , with his published papers , will constitute his true autobiography . Few stirring events happened to him ; his life , externally VOoL . XVII . b at least , was calm ; and equally calm was his mode of thinking , as evinced in his numerous scientific memoirs . He stayed in Edinburgh , studying with Dr. Hope , the well-known Professor of Chemistry , for two years , and there made the acquaintance and enjoyed the friendship of Leslie . Returning to Glasgow , he began to teach mathematics ; he then took a room for a chemical laboratory in Portland Street , and in this he gave lectures , for a very short time only , as he was Lecturer in the Aechanics ' Institute for the winter 1829-30 , having succeeded Dr. Thomas Clark , afterwards Professor in Aberdeen . In the latter year he was transferred to the Andersonian Institution , succeeding Dr. Ur , who went to London . Graham began in Glasgow with the good wishes of all who knew how laboriously he had studied . Ie was then 24 years old , but he had been known to scientific men for three years previously ; his earliest memoir bearing date 1826 , and one on diffusion of gases 1829 . He appeared extremely young , and like a boy beginning to teach . He was not fluent in speech ; there was a hesitation as if it were difficult to find the proper word ; and a quietness of demeanour which ( except for the little perceptible nervousness ) completely covered the great enthusiasm which kept him at constant work for forty years after that period . He remained in Glasgow lecturing and teaching in the laboratory till 1837 , and sending out diligent workers who have since shown themselves vigorous in the regions of science and its application to the Arts . In that year he went to London as Professor at the London University , now University College . HIe had his residence near it in Torrington Square , which he afterwards left for a house a few doors distant , at 4 Gordon Square , where he ended his days on the 16th of September , 1869 . In the College he was held in high regard by his pupils and colleagues . It is true that , as a lecturer , he had to contend with a want of natural fluency and with a feeble utterance ; but as he had always the clearest conception of the matter he was treating of , his manner of exposition , even of intricate subjects , was singularly clear and perspicuous , and the instruction imparted was well grounded and thorough , and was pervaded by the same philosophical spirit which guided him in his original investigations . In 1855 he ceased to be connected with the College , having succeeded Sir John Herschel as Master of the Mint . An occasional visit to Scotland to see his relationis , sometimes to Ballewin at Strathblane , a property which his father had left him , made up his chief journeys , and in later years he was afraid to go except in June or July . Iis chest , as indeed his whole constitution , was tender , and the accidental exposure to an open window in a warm August day brought on his final attack . Were it possible to write at present a correct accoul:t of Graham 's intellectual life , the space required would be too long for this occasion , and a short notice will be given of his principal papers only . His earliest memoir indicated in the ' loyal Society 's Catalogue ' is in Thomson 's I Annals of Philosophy , ' 1826 , " On the Absorption of Gases by Liquids . " He there reasons out the idea that gases are converted into liquids by mixing with or being absorbed by liquids , and that the phenomenon becomes simply that of two liquids mixed together . He concludes that gases may owe their absorption by liquids to their capability of being liquefied , and to the affinities of liquids to which they become in this way exposed . These two properties are considered to be the immediate or proximate causes of the absorbability of gases . It follows " that solutions of gases in liquids are mixtures of a more volatile with a. less volatile liquid . " He says also that it is a coincidence more than accidental that the gases which yielded to condensation in Mr. Faraday 's hands are , generally speaking , of easy absorbability . He objects therefore to Henry 's law , that the quantity of gas which water absorbs is directly proportionate to the pressure , because it is not likely that this law would have been spoken of had such gases as muriatic acid been employed , that being very readily absorbed , although there might be an approximation to such a law when the quantity of gas absorbed was inconsiderable . Graham illustrated the condensation and solution of a vapour in a liquid by supposing steam of the heat of 600 ? F. to be passed through sulphuric acid of 600 ? F. , when he doubted not immediate absorption and actual solution would take place , as if water and sulphuric acid were mixed at lower temperatures ; and yet the steam would be brought into the condition of a liquid which by ordinary cooling would have taken place only after nearly 400 ? diminution of temperature . So late as 1866 , speaking of the dialytic separation of gases through colloid septa , he is desirous of showing that the flow is not that of diffusion or of effusion , or of transpiration , but that of a liquid absorbed by one side and passed to the other ; and in 1868 he illustrates the passage of hydrogen through palladium by saying that it is analogous to liquid diffusion through a colloid . There are forty years between the beginning and end of this train of thought . This is a fair specimen of Graham 's habit of mind and of his perseverance . He seems to have begun life with an intense desire to know the inner structure of matter , stimulated to understand more than the atomic theory could give him , but nevertheless a true student of Dalton . Born in 1805 , when Dalton was preparing for the press the ideas he had already given in lectures , he seems to have been destined to begin a new line of work closely allied to that which Dalton had done . It is almost painful to think of the attempts of mankind to understand why bodies should have a definite composition , and Dalton 's simple idea of adding atom to atom not only made it appear possible , but showed why the contrary should be most improbable . Now it seems so simple that some men believe it was scarcely a discovery , whilst every chemist is slavishly bound to it in some form or other , unable either in practice or theory to escape ; and this point seems now to be true for all time . Still the simple b axiom , so to speak , was not a science ; and as one proposition after another arises out of it , the first idea itself appears grander and grander . Dalton , like Newton , used the term atom as meaninga particle which could not be divided by any force . But there seems no need to say that it could not be divided by the imagination or even by new forces , in which case it becomes the practical as opposed to the theoretical atom . Under the present chemistry there probably exists another which shall deal with the broken atom of our present science ; we do not know how many layers there may be under it . It is strange that Dalton 's idea was so purely mechanical , although illustrating a purely chemical act : there is no talk of obscure forces ; it is a movement like a carpenter 's , a fitting of pieces in the manner of a workman . Graham took up the subject in the same spirit , and seems to have during his whole life sought for nothing beyond the knowledge of the constitution of matter , and the mode in which the atoms or molecules move . His favourite word is molecule , not atom ; indeed he seems too guarded to use the latter in any ease of measurable movement . His destiny was to follow the progress of the molecule , and to show that there were movements in bodies which depended on that aggregration of atoms , whether ultimate atoms or not . Whilst Dalton showed the relative weights of the combining quantities , Graham showed the relative magnitude of groups into which they resolved themselves . Having discovered that solid bodies could be divided into two classes , colloid and crystalloid , and that the first consist of substances existing in great varieties of conditions , and apt to undergo long and remarkable progressive changes , he seems to have taught us the way to obtain many substances practically new , although nominally such as we have seen . Whilst one , the colloid , has power of motion in itself to a considerable extent , the other , the crystalloid , has power of motion in solutions , so that we are introduced to a series of new forces , the end of which is not in the faintest way foreseen . The door by which we enter these strange regions is found by a series of the most uninviting trials ; it seems to have been hidden under the most homely brushwood , and few would think of toiling so long in such a field . It may be well to go over some of his principal papers , and to observe how constantly he kept to these ideas whilst penetrating further into the subjects . In 1827 he observed that phosphate of magnesia effloresced very readily ; this , he argued , proved a weak affinity for water ; if weak , heat ought to destroy it , and so he found that it was thrown down anhydrous on boiling . lIe argues that it is only the hydrate that is soluble , properly speaking , in other cases also . This led him , in 1835 , to examine the hydrate , when he found that the tendency of phosphate of soda to combine with an additional dose of soda was connected with the existence of closely combined water . This induced him to separate the water of salts into two parts , crystalline and basic , the first being easily removed , the second requiring more than the boiling-point of water to remove it . This atom of water may be replaced by a salt , forming a class of double salts . Amongst the salts with basic water he puts sulphuric acid as sulphate of water , and an additional atom as equal to the atom of crystallization . In the same year he speaks of ammonia performing the function of water in compounds of copper . In 1836 he says that his " researches make it probable that the correspondence between water and the magnesian class of oxides extends beyond their character as bases , and that in certain subsalts of the magnesian class of oxides the metallic oxide replaces the water of crystallization of the neutral salt and discharges a function which was thought peculiar to water . " The inquiry was extended to the constitution of the phosphoric acids , and the amount of base taken up by them shown to be equivalent to the amount of water in the acid ; from this he passed to the arseniates . It is quite evident that he treated water as he treated metallic oxides ; indeed he speaks of metallic oxides performing the functions or taking the place of water . It was a distinct recognition of hydrogen as a metal in its place in salts , whilst his latest paper in 1869 endeavours to establish its specific gravity when combined with palladium as an alloy . This was one of the chains of discovery which , at an earlier period , led to the doctrine of substitution . It is still sound ; and although the water does not now hold the same place of honour in the phosphorus acids , the place is held firmly by the hydrogen , which takes its position as a metal . This idea cannot be regarded as originating with Graham ; Davy seems to have hinted it , and Dulong made it distinct ; but it was Graham whose careful experiments and cautious reasoning gave it consistency and force , although he himself did not actually adopt it in general teaching . Probably nothing tended so much to give hydrogen its present place as the inquiry into the constitution of the phosphates , and his explanation of the monobasic , bibasic , and tribasic acids . We have the first results of his experiments on diffusion in the Philosophical Magazine for 1829 . After giving various details of experiments he says , " It is evident that the diffusiveness of gases is inversely as some function of their density , apparently the square root of their density . " This is the conclusion he arrived at finally . The separation of gases by simple diffusion is shown to be practicable , and is there illustrated ; he mentions it as conceivable " that imperceptible pores and orifices of excessive minuteness may be altogether impassable ( by diffusion ) by gases of low diffusive power , that is , by dense gases , and passable only by gases of a certain diffusive energy . " Here we observe his wonderful caution : he will not say that the atoms or molecules may be too large , he will not say that the gas will not pass , but he says " impassable ( by diffusion ) . " *oo XXll In his paper read before the Royal Society of Edinburgh , Dec. 19th , 1831 , he goes more fully into his favourite subject , beginning with firmness . " It is the object of this paper to establish with numerical exactness the following law of the diffusion of gases . " " The diffusion or spontaneous intermixture of two gases in contact is effected by an interchange in the position of independent minute volumes of the gases , which volumes are not necessarily of equal magnitude , being in the case of each gas inversely proportioned to the square root of the density of that gas . " In this paper ( 1831 ) he also tried the speed with which gas passed through stucco under pressure . In 1846 Graham read to this Society a memoir " On the Motion of Gases . " There he showed what he called the effusion of gases into a vacuum through a thin plate ( - ? of an inch thick ) , " leaving no doubt of the truth of the general law , that differeint gases pass through minute apertures into a vacuum in times which are as the square roots of their respective specific gravities , or with velocities which are inversely as the square roots of their specific gravities , " and that " the effusion-time of air of different temperatures is proportional to the square root of its density at each temperature . " The remarkable results of transpiration are fully developed in his second paper ( June 21st , 1849 ) " On the Motion of Gases . " If a tube of a certain length be used to allow the escape of the gas , the velocities of the gases attain a particular ratio which remains constant with greater lengths and resistances . This ratio depends on a new and peculiar property of gases , which he called Transpirati6n . He considered that solids have many modes of showing their character , the varieties of structure being endless ; but gases could only show theirs in a few directions , and he believed that the ratios of transpirability would have a simplicity coinparable to that of the specific gravities , or even the still more simple relations of the combining volumes . As gases , compared with solids , are capable of small variation in physical properties , those characters which do show themselves may well be supposed to be the most deep-seated and fundamental with which matter is endowed . He adds , " It was under this impression that I devoted an amount of time and attention to the determination of this class of numerical constants which might otherwise appear disproportionate to their value and the importance of the subject . As the results , too , were entirely novel , and wholly unprovided for in the received view of the gaseous constitution , of which , indeed , they prove the incompleteness , it was the more necessary to verify each fact with the greatest care . " As examples , the density of nitrogen is 14 when hydrogen is taken as 1 ; but the transpiration velocity of hydrogen is exactly double that of nitrogen . The transpiration time of carbonic acid is inversely proportional to its density , when compared with oxygen . These results he believed to show " t the important chemical bearing of gaseous transpirability , and that it enmulates a place in science with the doctrines of gaseous densities and combining volumes . " This remarkable property of gases was viewed by Graham as a result of one of the initial endowments of matter , and in this search he showed his usual desire of approaching nearer than we had ever done to the actual constitution of the primitive molecule and practical atom . These inquiries on the motion of gaseous molecules led Graham to look at the motion of bodies in solution or " liquid diffusion . " The first paper was read in 1849 . the naturally connected this with his earlier experiments on the phosphates , and the amount of water held by them and phosphoric acid ; and he termed solubilities of substances weak and strong , as well as great or small . He supposed that this varying strength of solubility might arise from a greater or less diffusive power . Graham believed liquid diffusion to have an analogy to evaporation ; and as the squares of the times of equal diffusion of gases are in the ratio of their densities , so by analogy it might be inferred that the molecules of the several salts , as they exist in solution , possess densities which are to one another as the squares of the times of equal diffusion . Ie attributed the diffusion of substances in solution , like the transpiration of gases , to a fundamental property of bodies . The pith of the inquiry is thus stated:- " The fact that the relations in diffuision of different substances refer to . equal weights of these substances , and not to their atomic weights or equivalents , is one which reaches to the very basis of molecular chemistry . In liquid diffusion we deal no longer with chemical equivalents or the Daltonian atoms , but with masses event more simply related to each other in weight . Founding still upon the chemical atoms , we may suppose that they can group together in such numbers as to form new and larger molecules of equal weights for different substances ; or , if not of equal weight , of weights which appear to have a simple relation to each other . It is this new class of molecules which appears to play a part in solution and liquid diffusion , and not the atoms of chemical combination . " He seems glad to obtain the densities of a new kind of molecules , although knowing no more respecting them . One result is the formation of classes of equidiffusive substances ' ; these , again , led to a new mode of analysis in 1861 , and a new division of soluble bodies . It was observed that the power of diffusion of a solution of albumen was very small , 1000 times less than that of common salt ; and this fact led to an examination of numerous substances , when it was found that they divide themselves into two classes without respect to organic nature ; one is colloid , and includes gelatine and gelatinous silica , alumina , albumen , gums , sugar , starch , and extractive matter . The plastic elements of the animal body are found in this class ; and here Graham uses the word ( as , indeed , he uses all words ) in a very exact sense , that which has the power of forming . Continually seeking the origin of chemical action , he ascribes to bodies possessing this colloidal condition a dynamical character . They are slow in changing , but seem in a continual change . They possess energia , and may be the primary source of the force appearing in the phenomena of vitality ; and to these gradual colloidal changes may be referred the characteristic protraction of chemico-organic changes . These colloid bodies are very easily penetrated by the soluble crystalloid bodies to which they are opposed , and they form a medium also of separation or dialysis . This process of dialysis has a high value in the explanations it affords , and promises to afford , of many physiological phenomena . But these hitherto unknown and still obscure properties of molecules seem destined to lead us still further on ; and by presenting to us a nearer view of the fundamental phenomena , they give us an idea of the enormous magnitude of the structure under which they seem to lie . Graham believed that the rate of diffusion held a place in vital science not unlike the time of the falling of heavy bodies in the physics of gravitation . In a paper " ( On the Molecular Mobility of Gases , " June 18th , 1863 , he further compares several substances as to their facilities for diffusion , and defines clearly the effusion-rate and the transpiration-rate as distinct . A substance suiting the purpose of diffusion is graphite . He obtained by the graphite diffusiometer a separation of oxygen from the air , making a mixture with 2 per cent. additional of that gas . This led him to try another mode ; and by lengthening the surface and tube , he obtained 3per cent. more oxygen than in the atmosphere . This process he calls atmolysis . Trying diffusion without an intervening septum , he found that carbonic acid had proceeded half a metre length in seven minutes . The separation of gases was carried out much further , and described in a paper read June 21st , 1866 . Here he begins the use of caoutchouc , having been led to it by the experiments of Dr. Mitchell , of Philadelphia . He found that air drawn through sheet rubber contained as much as 41*8 oxygen , the theoretical speed being 40'46 , deduced from the passage of the separate gas . He is desirous of showing that in this case the flow is different from diffusion ; it is caused by an absorption of the gases , which are taken into the caoutchouc in a liquid state , and are then given out on the opposite side . This inquiry naturally led to an examination of the absorption by metals . Deville and Troost had discovered that platinum and iron absorbed gases when hot . Graham found hydrogen to pass through heated platinum 1'1 millim. thick at the rate of 489'2 cub. centimetres per minute on a square metre . Oxygen scarcely passed , and other gases tried did not pass . Wrought platinum took up 5'53 vols . of hydrogen , which , on cooling , were shut up or occluded in the mass . Fused platinum took only 0-171 vol. ; hammered platinum 2'28-3-79 . Palladium , however , was most remarkable , as it took up 643 vols . of hydrogen ; in a later paper the quantity is stated to be 935 vols . These gases were pumped out from the reheated , but could not be removed from the cold metal . Palladium cold , however , was found to take up hydrogen when it was used as the negative pole of a galvanic battery , and spongy palladium , which had absorbed hydrogen when heated , deoxidized some salts in the cold . Iron manufactured , or from telluric sources , was found to contain carbonic oxide . Silver , gold , copper , osmium-iridium took up little gas , and antimony no hydrogen . He divides the metals into crystalline and colloid . His paper of May 16th , 1867 , enters more fully into the subject , and shows that meteoric iron contains hydrogen , with the probability , if not certainty , that it was cooled in an atmosphere of that gas . Messrs. Huggins and Miller , as well as Father Secchi , had concluded that hydrogen is one of the gases shown on the spectrum of the fixed stars , and especially mentioned it as found with the unusual increased light of T Coronae in November 1866 . The actual handling of the gas brought from distant space was a strange experimental proof , and was remarkably characteristic of Graham 's peculiar inclination to place his work before his thought . He seemed to feel his way by his work . He was not able to impregnate iron with above one volume of hydrogen , whereas the meteoric iron contains at least three . He thinks this shows that it may have been absorbed under pressure . On May 22nd , 1868 , he showed that palladium took up 0 723 per cent. by weight of hydrogen ; and he inclines to believe that the passage of the gas through palladium is analogous to liquid diffusion through a colloid . As a private man , Graham led an uneventful life ; but no man has passed through the world more uniformly respected . Too retired , too quiet , his life appears to have a deep tinge of melancholy in it , notwithstanding its eminent success . Very intimate friends he had few out of the circle of the family of brothers and sisters , who were strongly attached to him , and to whom he was much devoted , being himself unmarried . As a scientific man , his claims were never disputed ; he was not called to assert his position , and he remained the undisputed head of his department . He received in early life ( 1834 ) the Keith Medal of the Royal Society of Edinburgh , and the Royal Medal of this Society in 1838 , and in 1862 the Copley Medal . He was made a Doctor of Civil Law of Oxford , Honorary Member of the Royal Society of Edinburgh , Corresponding Member of the French Institute and of the Academies of Berlin and Munich , and of the National Institute of Washington . His election into the Royal Society was in 1836 . On his appointment to the Mint , Mr. Graham laboured assiduously and successfully in acquiring a thorough knowledge of the technical work and financial relations of his office , and discharged his duties with much energy andjudgment . It is known that he brought about various reforms and economies in the working of the establishment ; but the service for which he will be chiefly remembered was the introduction of the new bronze coinage , which , besides substituting a more convenient medium of circulation than that in previous use , was attended with a pecuniary profit to the state of very large amount . An old and valued friend of Graham , Dr. A. W. Tofmann , then intimately associated with him , thus speaks of his administration of the Mint* : - " It would be difficult , within these narrow limits , to convey an adequate notion of the great and manifold activity exercised by Graham in the high office entrusted to him . The new chief of the Mint soon showed a vigilance , a knowledge of the work , an amount of industry and energy , and , when called for , an unsparing severity which astonished all , and especially some of the officials of the establishment . Such requirements had not heretofore been exacted , nor such control exercised . The new Master 's love of innovation , and his disturbance of settled arrangements ( for in such light was his action viewed ) , had to be resisted with every effort . The author of this sketch at that time held an office in connexion with the English Mint , and was therefore witness , though from without , of the struggle which Graham had to go through in his new position . It was years before he finally overcame these difficulties , and was enabled to return to his favourite study . " Graham , besides the memoirs mentioned and omitted here , wrote a system of chemistry . The second edition is still valuable ; it explained at a very early stage theories which are now general , although it did not actually adopt novel arrangements . The book is a masterpiece of clearness in arrangement and style , but it was written so slowly that the publisher said that to press him was like drawing his blood . The anxiety to be correct was painful . It gives a callness to all his writing , but really goes too far , as it rather represses the enthusiasm of the reader , and diminishes the force of the words . He may be said never to speculate till he has made experiments ; he seems to feel the forms with his fingers before he ventures to describe them ; but he reaches to utmost space in this manner more surely than others have done by the boldest imagination . He is , however , capable of the widest generalizations , and these he makes at times with surprising speed . When speaking of liquids , Graham has been quoted as saying that the rate of diffusion held a place in vital science not unlike the time of falling bodies in the physics of gravitation . We judge of the value of discoveries by the fruit they produce ; when we do so , it requires some time to judge fairly . Although there seems to us a boundless region opened up , it is not yet traversed ; perhaps he who opened it was best able to see its extent . By his experimental examinations of the motion of molecules , he has made a step which before was left to reason only ; and unless he can be shown to have made a mistake , we do right ( whilst associating him with other illustrious men of former times ) to connect him more closely with his most direct predecessor , Dalton . With such distinguished names , therefore , it seems just that we should , until the world shall teach us better , leave that of Thomas Grahanm.-R . A. S. MARIE-JEAN PIERRE FLOURENS , elected Foreign Member of the Royal Society in 1835 , was born at Maureilhan , near Beziers , Department of Heirault , in April 1794 . He studied Medicine at Montpellier , where he took his Doctor 's degree at the age of nineteen , and in the year following went to Paris . There he made the friendship of various eminent men , of whom are noted especially Chaptal and Frederick Cuvier , and devoted himself to the pursuit of Biological science , in which he soon attained reputation as a writer and original inquirer . His earliest and most important labours were directed towards the investigation of the functions of the nervous system , and on his experimental researches and writings on this department of Physiology , which continued afterwards to be his favourite pursuit , his scientific reputation may be said mainly to rest . The first fruits of these researches were made known in three Memoirs presented to the Academy of Sciences of Paris in 1822 and 1823 ; and subsequently published in an independent work entitled " Recherches Experimentales sir les proprietes et les fonctions du systeme nerveux dans les animaux vertebres . " Paris 1824 . Of this a second and greatly extended edition appeared in 1842 , containing the substance of Memoirs presented to the Academy since the publication of the first edition , with applications of the author 's doctrines to pathology and surgery , researches on the reunion of divided nerves , on the movements of the brain , on the pulsation of arteries , and on the effects of section of the semicircular canals of the ear also an extension of his previous inquiries to reptiles and fish . Following in the line of ialler , Zinn , Lorry , Saucerotte , Magendie , and others , Flourens endeavoured , by inflicting injuries experimentally on the encephalon and spinal cord , but especially by studying the effect of removal of definite portions of these organs , to assign the specific offices of the several parts of the cerebrospinal centre ; and whatever difference of opinion may prevail as to some of the physiological conclusions at which he arrived , it must be admitted that his experiments , which have for the most part been confirmed by later inquirers , have served in large measure as a basis of subseqruent reasoning on the subject . On his first coming to Paris Flourens became a writer in the Revue Encyclopcdique , ' and contributed articles to the 'Dictionnaire classique d'Histoire Naturelle , ' and in the course of his life published numerous papers on different anatomical and physiological subjects , besides that with which he was more enduringly occupied . The titles of these papers ( up to 1863 ) form a goodly array in the Royal Society 's Catalogue , to which we refer for details . The more notable of them are on the nutrition and growth of bone , on the structure of the skin and mucous membranes and on the epidermis and its appendages in man and animals , on the mechanism of Rumination , on vomiting in ruminants , and its non-occurrence in the Torse , on the vascular connexion of mother and foetus , &c. , while some are on questions of anthropology , comparative psychology , and natural history ; but although these writings are for the most part founded on actual observation and real work , it can scarcely be said that they rise above mediocrity . Flourens 's first and most important memoir on the nervous system became the subject of a commendatory and most instructive report by Baron Cuvier in 1822 , whose friendslip and favour he thenceforth enjoyed . Cuvier a few years after ( in 1828 ) entrusted Flourens ( as his deputy ) with the delivery of the lectures on Natural I-istory at the College of France , and two years later appointed him in like manner to give the lectures on Human Anatomy at the ' Jardin du Roi , ' in which appointment he was confirmed as Professor in 1832 . In 1835 he became Professor in the College of France . Thoutgh rising in fame , it was probably through Cuvier 's influence , more immrediately , that Flourens was in 1828 elected aM ember of the Institute , in succession to Bosc . In 1833 he was appointed one of the perpetual Secretaries , on the retirement of Dulong . In this latter capacity he furnished from time to time eloges of various distinguished members of the Academy deceased during his tenure of office . These productions of his pen , as well as his official reports and his writings generally , were highly esteemed for their literary merit , and no doubt led to the muchcoveted distinction he received of being elected into the Academy FranSaise in 1840 . While recognizing M. Flourens 's undoubted merits , we are nevertheless constrained to remark that , measured by them , his career as regards both social and scientific distinction , was singularly prosperous . Besides holding a hilhly influential position in affairs of science , he was elected a Member of the Chamber of Deputies for the Arrondissement of Beziers in 1837 , and in 1846 he was created a Peer of France . HIe still , however , retained his professorship , and suffered neither honours nor revolutions to interrupt his scientific work . In his latter years he was affected with softening of the brain , ending in general paralysis , to which he succumbed , at his country seat Mont Geron , in the Department of Seine at Oise , on the 6th of Decem:ber 1867 . HIe has left three sons . PETER MARK ROGET , M.D. , died on the 12th of September , 1869 , in his 91st year . For the last 54 years he had been a Fellow of the Society , and during 21 of these had filled the office of Secretary . The earlier events of his life belong to a former page of the world 's history , and to a generation that has passed away . He was born in London , in Broad Street , Soho , on the 18th of January , 1779 . His father , the Rev. John Roget , was a native of Geneva . When about 25 years old he came to reside in London , as Minister of the French Church in Threadneedle Street , founded by Edward VI . , and was , two years afterwards , united in marriage with Catherine , only surviving sister of the illustrious Sir Samuel Romilly , then a young man of about 20 , between whom and Mir . Roget a warm friendship had arisen , together with sentiments of the highest mutual esteem . The subject of the present memoir was the only son of this marriage . He had the misfortune to lose his excellent father very early in life . Not five months after his birth his parents were compel'ed to leave him in England and hasten to Geneva , on account of Mir . Roget 's declining health . Two years afterwards the child was brought to them by his uncle , Mr. iomilly , who was then studying the law ; and in two years more , under the same escort , the widowed mother returned to England with her son , and a daughter that had been born a few weeks only before the father 's death , wh-ich event happened in Maay 1 783 . In the following year the Rogets resided in Kensington Square , in the family of Mr. Chauvet , of Geneva , who kept a private school , where much of the character of parental intimacy was infused into the ordinary relations of teacher and pupil . Here the boy received the rudiments of education ; but he was no doubt mainly indebted for his early training to the devoted care of his mother , who was admirably qualified for the task , not only by her mental acqu-irements , but by a systematic habit of mind , which was inherited by her son in a marked degree . At a very early age , moreover , he began the practice of self-instruction ; and having conceived a strong taste for mathematical studies , which he pursued without aid or even encouragement from others , he soon made considerable progress in the elements of science . Although from time to time returning to Kensington , Mrs. Roget and her two children spent the greater part of the ten years next after her husband 's death in short sojourns in the provinces . 'This was an eventful period of history ; and , late in life , Dr. Roget remembered how , during a summer spent at Malvern , the news arrived of the taking of the Bastille , and how while at Dover they used to see the emigrants landing from France and thanking God for their deliverance . In the year 1793 , the mother with her two children took up their residence in Edinburgh , where Roget , then 14 years old , was entered at the University , which was then at the height of its fame . During the first two years of his residence there he attended the classes of Humanity ( Dr. Hill ) , Greek ( Mr. Dalzell ) , Chemistry ( Dr. Black ) , Natural Philosophy ( Greenfield ) , and Botany ( Dr. Rutherford ) . In the summer of 1795 his studies were agreeably varied by a tour in the Highlands , in company with his uncle Romilly and their attached friend Mr. Dumont , well known in connexion with the writings of Bentham , and as author of the ' Souvenirs sir Miirabeau . ' To the early guidance of the last-mentioned companion , who took a warm interest in his welfare , and was at especial pains to aid the cultivation of his intellect , Dr. Roget was wont to attribute the enlightened principles which governed his conduct throughout life . IIe entered the medical school in the ensuing winter , and attended during that and the two following years , the lectures d of Dr. Monro on Anatomy , Drs. Black and Hope on Chemistry , Mr. John Allen on the Animal Economy , Drs. Wilson and Gregory on the Practice of Medicine , Dr. Hamilton on Midwifery , Dr. Home on Materia Medica , Dr. Duncan and Mr. James Russell 's Clinical Lectures , and , to his especial interest and delight , those on Moral Philosophy , by Professor Dugald Stewart , from whom he received much kindness , and for whom he always expressed a peculiar regard . While thus diligently engaged , he was in the summer of 1797 prostrated for a time by a severe attack of typhus fever , which he caught in the wards of the Infirmary , and which nearly proved fatal . On the 25th of June , 1798 , he took his degree of M.D. , being then only 19 years of age . The subject of his thesis , which he dedicated to his uncle Romilly , was " 'De Chemicae Affinitatis Legibus . " In the same year he wrote a letter to Dr. Beddoes on the non-prevalence of consumption among Butchers , Fishermen , &c. , which is published in that writer 's Essay on the Causes &c. of Pulmonary Consumption , ' London , 1799 . After a summer and autumn spent in a trip to the Falls of the Clyde and the English Lakes , and a succession of visits to Dr. Darwin at Derby , Mr. Keir ( the Chemist ) near Birmingham , Dr. Beddoes at Clifton , and the Marquis of Lansdowne at Bowood , Dr. Roget came to London and continued his professional studies , first at Dr. Willan 's Dispensary in Carey Street , and shortly after as a pupil of St. George 's Hospital , where he attended Dr. Baillie 's lectures in the early part of 1799 . In that year he wrote a letter to Davy on the effects of the respiration of the then new gas ( oxide of azote , or nitrous oxide ) , which communication appears in Sir Humphry Davy 's 'Researches , ' published in 1800 . In October 1800 , Dr. Roget spent six weeks with Mr. Jeremy Bentham , who it is understood consulted him at that time upon a scheme which he was concocting for the utilization of the sewage of the metropolis . It may easily be imagined with how great an interest that most remarkable man was regarded by the young physician . In November he began to attend Abernethy 's lectures at St. Bartholomew 's -Iospital . At the end of the following year he went to Manchester on an engagement to travel with the two sons of Mir . John Philips of that town ; and it was while thus employed that he met with an adventure which he ever after regarded as forming the great crisis of his life . The peace of Amiens having thrown open the continent to English tourists , Dr. Roget and his two pupils spent about three months in Paris in the early part of 1802 , and thence proceeded in the summer to Geneva , having for their travelling companion thither Mr. Lovell Edgeworth , brother of the authoress Maria Edgeworth . There Dr. Roget found his old friend and preceptor Chauvet , and stayed for some time at his house . The succeeding winter was spent amidst the congenial society of Geneva , and in forming plans for a summer tour in Switzerland . These prospects were , however , suddenly dispelled by the news of the rupture of peaceful relations between England and France , of which country Geneva then formed a part . This was soon followed by Bonaparte 's celebrated order to arrest all the English then in France , and above eighteen years of age . On the first rumour which reached Geneva of this measure on the part of the First Consul , Dr. Roget determined to retire at once with his pupils into Switzerland ; but on attempting to do so discovered , to his dismay , that the most active measures had been taken to prevent their escape . Their only course was to submit . The two Philipses were passed as under 18 , but Roget was detained prisoner on parole . This state of things lasted for about six weeks ; and in the mean time fresh rumours reached Geneva of a contemplated deportation of the English prisoners into the interior . While Dr. Roget was considering what steps he should take under these circumstances , he suddenly received the startling intelligence that in about a week 's time all the English in Geneva were to be sent to Verdun , and that those in Switzerland were already arrested . Dr. Roget then , as a last resource , applied to the authorities for exemption from arrest , on the ground that he was entitled to the rights of a citizen of Geneva by virtue of his descent from Genevese ancestors . This claim was fortunately admitted ; and two days afterwards he saw the rest of the English , with poor Edgeworth among them , set out for Verdun . Dr. Roget and his young companions now lost no time in leaving the country , but a long detour had still to be made ere they could reach England . The French were rapidly extending their boundaries westward , and the travellers found it necessary to proceed by way of Stutttgart , Frankfort , Leipsick , Potsdam , Berlin , Lubeck , and Ifusum , whence they sailed for England , reaching Harwich on the 22nd of November . On the way the elder Philips fell ill of a fever , which detained them for two months at Frankfort . Dr. Roget thereby made acquaintance with the celebrated anatomist Soemmering , whom he called to his aid in attending the patient . In the spring of 1804 he repaired to Edinburgh with the intention of pursuing his studies , but was called from thence to Bath to attend upon the Marquis of Lansdowne , whom he accompanied to Hlarrogate , and afterwards to Bowood , as his private physician , remaining with him till the 11th of October . Being then in his 26th year , and desirous of establishing himself in practice , he took up his residence in Manchester , where , on the death of Dr. Percival , there appeared to be an opening in his profession . He was in the same month appointed one of the physicians to the Infirmary , an institution comprising a large Hospital and Dispensary , a Fever HIouse , and a Lunatic Asylum . Dr. Roget is regarded as having , in conjunction with his colleagues , Mr. Gibson and Mr. Hutchinson , laid the foundation of the Medical School in Manchester . In the winter of 1805-6 he gave with them , a joint course of lectures to the pupils of the hospital on Anatomy and Physiology , himself taking the latter subject and delivering eighteen lectures from 29th January to 31st March , 1806 . In the midst of this apparent devotion to pursuits for which he had shown so much natural taste , and which seemed to promise him success in life , he , strange as it may appear , accepted in November 1806 the appointment of private secretary to Lord Howick , then Secretary of State to the Foreign Department , and afterwards Earl Grey . le very soon , however , became conscious of a dislike for the service , and quitted it in a month , returning to Manchester , where he busied himself again in an occupation in which he was destined to rise to eminence . In the lectures he had already delivered he had introduced , in addition to the subject of Human Physiology , as already taught in the school , a comparative survey of the functions of animals , with a view to its forming a useful branch of general knowledge . Encouraged by this first attempt , he commenced , in January 1807 , a more popular course on the Physiology of the Animal Kingdom , at the rooms of the Philosophical and Literary Society . This Society numbered among its then members men of high distinction in science and general attainments . In its proceedings Dr. Roget took an active part , and he was one of its Vice-presidents . His lectures , fifteen in number , were delivered in the evenings twice a week , and were well attended and highly esteemed . Dr. Roget resigned his post at the Infirmary in October 1808 , and transferred the scene of his labours to London , where he established himself in the following January in a house in Bernard Street , Russell Square , and on the 3rd of March was admitted Licentiate of the Royal College of Physicians . He lost no time in commencing on a wider field , the career which had been indicated to him by his success in Lancashire . An opportunity soon offered itself . The Russell Literary and Scientific Institution had been opened in the preceding year under the management of a number of distinguished residents in the neighbourhood , including his uncle , then Sir Samuel Romilly , Mr. James Scarlett ( afterwards Lord Abinger ) , Mr. Francis IHorner , &c. ; and Dr. Roget and Mr. Pond ( the Astronomer Royal ) were chosen to inaugurate the first lecture season , in the spring of 1809 , by the delivery of two courses of twelve afternoon lectures , the one on Animal Physiology , the other on Astronomy . Dr. Roget 's course , repeated in the following year , proved to be the first of a long series on his favourite subject , which established for him a high reputation , in a career of more than thirty years ' duration as a public lecturer . It will be convenient here to give a list of these courses . Besides his lectures at Manchester in 1806 and 1807 , and at the Russell Institution in 1809 and 1810 , he lectured on the same subject at the Royal Institution in the spring of 1812 , 1813 , 1814 , 1822 , and 1823 ; at the London Institution in the spring of 1824 ; at the two last-named places concurrently in the spring of 1825 ; in 1826 , at the London Institution in the spring , and at the new Medical School in Aldersgate Street in the autumn ; and finally at the Royal Institution in the spring of 1835 , 1836 , and 1837 , as the first Fullerian Professor , to which chair he was nominated by the founder , Mr. John Fuller . In these courses , which numbered from ten to eighteen lectures each , his favourite arrangement of the subject was that which he had adopted in 1807 . After a general survey of Cuvier 's classification , he would treat , first , of the mechanical functions ; secondly , the chemical functions , circulation , respiration , and nutrition ; and thirdly those of the nervous system , and the intellectual faculties . At Aldersgate Street he also dealt with the function of reproduction and evolution . Sometimes , however , he divided his subject zoologically , and dealt separately with each class of animals . In his earlier lectures he made Hluman Physiology the basis of his comparison , which plan he appears to have gradually exchanged for that in which the interest rises as the scheme of nature is reviewed in successive stages from the lower to the higher orders of the animal kingdom . At the Royal Institution in 1825 and 1836 , and at the London Institution in 1826 , he confined himself to one department , namely , that of the External Senses . The introductory lecture at the Aldersgate School was published by Longman and Co. in 1826 , and of many of his lectures he furnished the abstracts published in the Literary Gazette . In all these discourses Dr. Roget kept in view what he had announced at Manchester as his leading object , namely , " to point out , on the plan pursued by Dr. Paley , those proofs of infinite wisdom and benevolence which are displayed in every part of the universe , but which are nowhere so eminently conspicuous as in the structure and economy of the animal creation . " In October 1809 he projected the foundation of the Northern Dispensary , which , with the cooperation of many influential neighbours , was opened in the following June , with Dr. Roget as its physician . The active duties of this office he performed gratuitously for the next eighteen years . In 1825 he was presented with a handsome piece of plate by the patron and governors . In 1810 he began to lecture on the Theory and Practice of Physic at the Theatre of Anatomy , Great Windmill Street , in conjunction with Dr. John Cooke , who two years afterwards resigned him his share of the undertaking . Dr. Roget then delivered two courses a year until 1815 . Among his colleagues there , were Sir Benjamin Brodie , Sir Charles Bell , Mr. Brand , and other leading men of science . In 1811 he was chosen one of the secretaries of the Medical and Chirurgical Society of London , of which he had been one of the earliest promotors in conjunction with his fiiends Drs. Marcet and Yelloly . In the same year he published a paper in the Medico-Chirurgical Transactions , vol. ii . p. 136 , on " A Case of Recovery froom the effects of Arsenic , with remarks on a new mode of detecting the presence of this Metal , " to which he afterwards added a note in vol. iii . p. 342 . In 1812 he wrote an article in the Edinburgh Review , vol. xx . p. 416 , on P. Huber 's ' Recherches sir les Moeurs des Fourmis Indigenes . ' I-e was also the writer of the Review in vol. xxv . p. 363 , of the same author 's 'Nouvelles Observations sir les Abeilles . ' While engaged in these avocations , as well as in professional practice , which about the year 1813 began to be considerable , Dr. Roget was not unmindful of his early passion for the exact sciences . Of Mathematics and Natural Philosophy he made a practical study ; and in the year 1814 he contrived a sliding-rule so graduated as to be a measure of the powers of numbers , in the same manner as the scale of Gunter , then in common use , was a measure of their ratios . It is a logo-logarithmic rule , the slide of which is the common logarithmic scale , while the fixed line is graduated upon the logarithms of logarithms . The consequence is that powers are read as easily as products are on the common rule , and the arrangement is such that high powers of quantities little exceeding unity , so much wanted in compound interest , statistics , &c. , are read off on a single setting . I-is paper thereon , which also describes other ingenious forms of the instrument , was communicated by Dr. Wollaston to the Royal Society , and read on the 17th of November , 1814 . It appears in the Philosophical Transactions for 1815 , p. 9 . It was through this communication that he gained admission to the Society . He was elected Fellow on the 16th of March , and admitted on the 6th of April , 1815 . The date of this epoch in his life is noteworthy in relation to the importance which he attached to his deliverance in 1803 from the clutches of Bonaparte . The year in which his paper was read was that of his young friend Edgeworth 's release . The manner in which the interval had been employed affords a measure of the loss which he and others would have incurred had he been destined to the like exile . The next decade in Dr. Roget 's life was a period of active industry , passed in the society of many of the most distinguished men of his time . Besides his occupations above specified , he employed his pen in the production of various published writings . In 1815 he contributed a paper to the MedicoChirurgical Transactions , vol. vii . p. 290 , " On a Change in the Colour of the Skin produced by the internal use of Nitrate of Silver . " At various periods between 1815 and 1822 he wrote the following treatises and articles in the Supplement to the sixth edition of the 'Encyclopaedia Britannica ; ' viz. ANT , APIARY , BARTIEZ , BEDDOES , BEE , BICIAT , BROCKLESBY , BROUSSONET , CAMPER , CRANIOSCOPY , CURRIE , DEAF AND DIUMB , KALEIDOSCOPE , and PHYSIOLOGY . In 1818 he wrote a letter " On the Kaleidoscope " to the Editors of the ' Annals of Philosophy , ' which was published in vol. xi . p. 375 . That year was saddened by the melancholy death of his uncle , Sir Samuel Romilly . In July 1820 he was appointed Physician to the Spaniish Embassy , which office he retained for many years . In the same year he wrote a letter to MAr . Travers on a voluntary action of the Iris , which was published by Mr. Travers in his work ' On the Diseases of the Eye ; ' and an Appendix to Larkin 's ' Introduction to Solid Geometry and to the Study of Crystallography , ' in which Dr. Roget demonstrates the ratios subsisting between the volumes of solids composing the artificial series , together with the various inclinations of their faces . In 1821 he wrote " Observations on Mr. Perkins 's Account of the Compressibility of Water , " in the ' Annals of Philosophy , ' N. S. vol. i. p. 135 ; and in 1822 , a Biographical Memoir of his valued friend and frequent fellow-worker Dr. Alexander Marcet , in the 'Annals of Biography and Obituary ' for 1823 . In 1823 he is quoted by Dr. Cooke in his work on Epilepsy , pp. 147 , 151 , & 215 . On the 1st of May in the same year he was appointed Physician to the General Penitentiary , Milbank , in conjunction with Dr. P. M. Latham , on the occasion of an epidemic dysentery which prevailed among the prisoners . Htis labours there occupied him for fifteen months ; and in 1824 appeared the joint report of himself and his colleague to the House of Commons . In the autumn of that year was another great epoch of his life , namely that of his marriage . Dr. Roget married Miss Hobson , only daughter of Mr. Jonathan Iobson , a merchant of Liverpool . The union was one of unclouded happiness , but of short duration . Mrs. Roget , after giving birth to a daughter and a son , died in the spring of 1833 , of a lingering disease . On the 9th of December , 1824 , another mathematical paper of Dr. Roget 's was read at the Royal Society ; this is entitled " An Explanation of an Optical Deception in the appearance of the Spokes of a Wheel seen through vertical apertures " ( Phil. Trans. for 1825 , p. 131 ) ; and in 1825 he wrote another in the 'Scientific Gazette , ' Nov. 5 and 12 , " On an apparent violation of the Law of Continuity . " In 1826 , besides his " Introductory Lecture , " there appeared an article by him on Electro-Magnetism in the 'Quarterly Review , ' being a review of Ampere 's 'Recueil d'Observations Electro-Dynamiques , ' and Barlow 's 'Essay on Magnetic Attractions ; ' and an article " On the Quarantine Laws , " in the Parliamentary Review , p. 785 . In 1827 he received a commission , with Mr. Telford and Mr. Brand , under the Great Seal , to inquire into the supply of water to the Metropolis , which resulted in the publication of their report in 1828 . He began at this time the composition of the series of treatises in the 'Library of Useful Knowledge ' on " Electricity , Galvanism , Magnetism and Electro-Magnetism . " They were issued in parts in the years 1827 1829 , and 1831 , and were afterwards published together in one volume . These treatises were held in considerable repute at the time they were published , and that on Electricity reached a second edition . He also wrote the article GALVANISM in the 'Encyclopedia Metropolitana . ' His connexion with the Society for the Diffusion of Useful Knowledge , for which the above treatises were written , is thus referred to by Mr. Charles Knight , in his ' Passages of a Working Life ':- " Amongst the founders of this Society , Dr. Roget was , from his accepted high reputation , the most eminent of its men of science . He was a vigilant attendant on its committees ; a vigilant corrector of its proofs . Of most winning manners , he was as beloved as he was respected ... . Upon all questions of Physiology , Peter Mark Roget and Charles Bell are the great authorities in the Useful Knowledge Society . " On the 30th of November , 1827 , Dr. Roget was elected Secretary of the Royal Society , on the retirement of Mr. ( afterwards Sir John ) Herschel . ' In company with his friend Dr. Bostock in 1828 , and again with Mrs. Roget in 1830 , shortly after the " three days " revolution of that year , he revisited Paris , with what recollections it is easy to imagine . In the former year a distinguished friend of Dr. Roget 's died , for whom he had a peculiar veneration , namely Dr. Wollaston , and in 1829 he lost his early adviser , Dumont . In 1829 and 1830 he occupied the chair as President of the Medical and Chirurgical Society , of which he had ceased to be secretary three years before . In 1828 he wrote an article in the 'Parliamentary Review ' on " Pauper Lunatics ; " and in 1831 he contributed to the ' Journal of the Royal Institution of Great Britain , ' vol. i. p. 311 , a paper " On the Geometric Properties of the Magnetic Curve , with an account of an Instrument for its mechanical description . " In June in the same year he was elected , speciali gratia , Fellow of the Royal College of Physicians , and in the following May he read the ' Gulstonian Lectures , ' for which he selected as his subject " The Laws of Sensation and Perception . " An abstract of them , written by him , appeared in the ' London Medical Gazette ' for that month . In 1832 he furnished the articles AGE and ASPHYXIA to the ' Cyclopaedia of Practical Medicine , ' published under the superintendence of his friend Dr. Tweedie . Before this time , but at what precise date has not been ascertained , he had written the following articles in 'Rees 's Cyclopaedia ; viz. SWEATING SICKNESS , SYMPTOM , SYNOCHA , SYNOCHiUS , TABES , and TETANUS . The year 1833 was one of great trial . The absorbing grief which he suffered on the death of his wife made other sorrows seem light ; but several family afflictions occurred at the same time . Dr. Roget sought to divert his mind in the society of his scientific friends , and in the interest he could still take in scientific pursuits . He attended the Meeting at Cambridge of the British Association , which had been founded two years before at York . These gatherings were always a source of great delight and interest to him , and he was a frequent attendant at them for the next thirty years . At one or more of the earlier Meetings he filled the chair of the Physiological Section . Fortunately also he was at this time engaged in an undertaking with which his memory will ever be associated , namely , the production of one of the ' Bridgewater Treatises . ' The most important department of that celebrated series , executed under the will of the Earl of Bridgewater , to illustrate " the Power , Wisdom , and Goodness of God , as manifested in the Creation , " had been assigned to Dr. Roget by the late President of the Royal Society , Mr. Davies Gilbert , to whom the selection was ex ofcio in . trusted . His treatise , which forms the fifth of the series and is in two volumes , has for its title " Animal and Vegetable Physiology considered with reference to Natural Theology . " As the testator had specified " the effect of digestion , and thereby of conversion , " and " the construction of the hand of man , " as instances of the " reasonable arguments " whereby the collective work was to be illustrated , were departments assigned to other writers , to be dealt with in separate treatises ; but with these exceptions , Dr. Roget 's province was to embrace nearly the whole of the physiology of the two kingdoms of nature . Of the manner in which he performed the task it is needless to speak at length here . As the prescribed purpose of the work was the very object which he had set before him and retained in view ever since his early efforts at Manchester , he naturally adopted the arrangement which he had found best in his lectures , and he endeavoured to embody in the form of a compendium so much of the argument and such of the illustrations as were adapted to every class of readers , and might form a useful introduction to the study of Natural History . Since the time of Roget the science of Comparative Anatomy has entered upon new phases , then but dimly foreshadowed ; but still his Bridgewater Treatise may be read with profit and delight by all , on account of the deeply interesting nature of the subject , the lucidity of the argument , the variety of illustration , the pure religious tone which pervades it , and the admirable style in which it is composed . Of the work in its original form three editions were published the first and second in 1834 , and the third in 1840 ; and two years before his death , the author superintended the ' passing through the press of a fourth edition , published by 1Messrs . Bell and Daldy . Dr. Roget was the last survivor of the authors of the Bridgewater Treatises . In the years 1834 and 1835 he held the office of Censor to the Royal College of Physicians . In 1837 and subsequent years he took an active part in the establishment of the University of London , of the Senate of which he remained a member until his death ; and in June 1839 he was appointed Examiner in Physiology and Comparative Anatomy , which office he held for some years . In 1838 his pen was again employed by the editors of the 'Encyclopaedia Britannica , ' to the seventh edition of which he contributed the articles BANKS ( Sir Joseph ) , PHRENOLOGY , and PHYSIOLOGY . The last two were published separately in two volumes . That on Phrenology was , with some additions , a reprint of the article " Cranioscopy " belonging to the former edition . In the original article he had expressed his strong dissent from the conclusions of the phrenologists , and this had given rise to answers on their part , particularly by Mr. George Comb , in " Essays on Phrenology , " Edinb . 1819 , and by Dr. Andrew Comb in the 'Phreno . logical Journal . ' To these criticisms , which were at least a tribute to the ability with which he had argued his case , Dr. Roget took this opportunity to reply . The article " Physiology " was an entirely new and comprehensive treatise , describing the various functions of the animal economy . That which he had before written under the same title was confined to the philosophical department of the subject , containing an analytical investigation of the several classes of vital powers and their mutual relations , and pointing out the necessity of distinguishing , more carefully than bad been done by early inquirers , between physical and final causes . In 1844 Dr. Roget again travelled abroad , revisited Geneva , and took the opportunity of attending the Meeting of the Italian Scientific Association held that year at Milan . In other respects his public life during his long term of office as Secretary was intimately associated with the annals of the Royal Society . In the course of that time changes had been introduced which rendered the duties of the Senior Secretary exceedingly laborious . Not only did the task of editing the Proceedings both of the Society and of the Council fall to his share , but also that of making and preparing for publication the Abstracts of Papers read . This labour was performed by Dr. Roget from November 1827 until his retirement from office in 1848 . Ever devoted to the interests of the Society and to his own important duties , he at times found his position one of great delicacy , and his name had occasionally to appear in the front rank of polemical warfare . On these occasions he maintained his position by firmness and forbearance , while sometimes smarting under undeserved attacks . On the 7th of November , 1836 , a vote of thanks was accorded to him by the Society . On retiring from office , although in his seventieth year , he at once embarked in a laborious undertaking which he had projected many years before . As long ago as the year 1805 he had formed , for his own use in literary composition , a small classed catalogue of words , which vocabulary had often proved of great service to him in his writings . This he determined to expand into a work of general utility , and after three or four years of labour he published , as its result , the now well-known 'Thesaurus of English Words and Phrases , classified and arranged so as to facilitate the expression of ideas , and assist in Literary Composition . ' The appreciation which the work has received may be inferred from the fact that it has reached a twenty-eighti edition . It first appeared in 1852 , and after running through two editions , was reduced to a more portable form , and stereotyped . Not the least remarkable part of the work is the arrangement , at once philosophical and practical , of the Ideas , which forms the basis of the classification . The book may be shortly described as the converse of an ordinary dictionary . A dictionary sets forth the idea belonging to a given expression ; the ' Thesaurus ' supplies the expression to a given idea . A French 'Thesaurus , ' in which the author , Mr. T. Robertson , adopted in all its details Dr. Roget 's arrangement , was published in Paris in 1859 , with the title " Dictionnaire Ideologique . Recueil des Mots , des Phrases , des Idiotismes , et des Proverbes de la Langue Fran ? aise classes selon l'ordre des Idees . " An imitation of the original work , but omitting all the phrases from the classification , was also produced in America . With the publication of the ' Thesaurus , ' Dr. Roget 's public career may be said to have closed . le had for many years retired from practice , and now an increasing deafness excluded him to a great extent from the pleasures of social intercourse . This infirmity , which was almost the only sign of his great age , he bore with patience and resignation . He had survived all the friends of his youth and most of those of his manhood ; but he was happy in the possession of mental resources , which enabled him to indulge , even to his last day , the habits of constant industry which he had acquired when a boy . As with advancing age he became less inclined for , and at last less capable of , deep study or long-sustained thought , his employments partook more of the nature of pastimes ; but both in his selection and pursuit of these there might still be traced the scientific turn of thought and philosophical love of method which had characterized the main achievements of his life . The engines he had forged to store his mind were now employed to entertain his leisure . One example of this was very remarkable . At an early period ( May 1811 ) he had attended a course of lectures by the celebrated Feinaigle , of whose system of Mnemonics he made constant use throughout life . This system comprises two main devices for a memoria technica . The one is designed to record chronological facts , or indeed any facts connected with the ordinary succession of numbers , the other to impress separate figures upon the memory . The first object is accomplished by a methodical arrangement in well-known portions of space , such as the sides of a room ; the second by means of words which can be easily remembered , and of which the letters are made to represent figures under a conventional rule of interpretation . Of both these sources Dr. Roget had availed himself largely . He had applied the former to a great variety of subjects . For him familiar places had thus an additional interest . The houses he had lived in , and those of friends whom he had visited , the old rooms of the Royal Society at Somerset House , and of various Institutions which he frequented , were pictured to his mind 's eye as peopled with an infinitude of facts , and teeming with varied information . The chronicle of universal history , the measurement of earth and sky , the epochs of his life and of those of his contemporaries , the sources of his income , the categories of his 'Thesaurus , ' the general arrangement of human knowledge , were all recorded in this manner on the tablets of his memory . Of the second device , he had also made extensive application . Logarithms , approximations to surds , and various ratios in common use in computation were set by him to doggrel phrases , which it was an amusement to repeat to himself as he walked ; and he would sometimes astonish his acquaintance by accurately stating the value of r to forty or fifty places of decimals . He was always fond of mechanical contrivances , and at one period spent much time and labour in attempts to construct a calculating machine . This design he abandoned on seeing the beautiful engine of Professor Scheutz , of which he at once admitted the superiority . He also made some progress towards the invention of a delicate balance , in which , to lessen the effect of friction , the fulcrum was to be within a small barrel floating on water . Scientific toys were a source of great delight to him , as has been already seen in his study of the kaleidoscope . Late in life he amused himself much with conversions of plane rectilinear figures of equal areas-cutting out pieces of card so that they could be differently put together to prove the equality , and thereby forming a series of geometrical recreations . He was also fond of exercising his ingenuity in the construction as well as the solution of chess problems , of which he formed a large collection . Some of those figured in the 'Illustrated London News ' were of his invention . To assist persons interested in the same pursuit , he contrived and published ( in 1845 ) a pocket chess-board , in which small men of card , lying flat on the board , were kept in place by the insertion of their bases into folds or pockets in the chequered paper which composed it . In the 'London and Edinburgh Philosophical Magazine ' for April 1840 , there is a " Description of a Method , " which he invented , " of moving the Knight over every square of the chess-board without going twice over any one ; commencing at a given square and ending at any other given square of a different colour . " The complete solution of this problem , which had engaged the attention of some of the most eminent mathematicians , including Euler and De Moivre , had never been effected before . During his latest years , which were passed in complete retirement , he derived great amusement from light epigrammatic literature , still collecting and classifying according to his wont ; but his chief resource was in the pages of his ' Thesaurus , ' to which he continued to make additions until the last day of his life . His constant spirit of cheerfulness as his end drew nigh , and the kindness and benevolence which endeared him to all around , befitted a life spent in accordance with his belief that the purpose of our existence here on earth is that of doing good to our fellow creatures in furtherance of God 's everlasting glory . After spending last summer at Malvern in the enjoyment of his usual health , his strength failed him during the great heat of August , and on the 12th of September he expired , peacefully and without suffering , from the natural decay of that vital power the mysterious working of which he had so laboured to illustrate . Dr. Roget was also Consulting Physician to Queen Charlotte 's Lying-in Hospital ; Hon. Member of the College of Physicians in Ireland ; Fellow of the Astronomical , Entomological , Geographical , Geological , and Zoological Societies , and the Society of Arts ; Member of the Royal Institution ; Hon. Member of the Institute of Civil Engineers , of the College of Physicians in Ireland , and of the Literary and Philosophical Societies of Liverpool , Bristol , Quebec , New York , Haarlem , Turin , Stockholm , and Athens . He was also a member of a variety of social scientific clubs , among others , an Honorary Member of the Smeatonian Society of Civil Engineers ; and he was at the time of his death the " father " of the Royal Society Club , of which he had been a member since 1827 .

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ERRATA.\#x2014;PART III.

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Astronomy

Formulae

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ERRATA . PART III . In Mr. Herschel 's Paper on the Parallax of the Fixed Stars . Page 272 , line 21 , for\#171 ; * sin. I " read " sin. X. " --274 , line 15 , for " sin. I " read " sin. X. " 274 , line 17 , instead of the equation there set down , read as follows : Sin. X. tan . ( \#169 ; 1 ) = tan . ( *r c ) ; ( 2 ) In consequence of these corrections , the dates in Col. 5 of the table page 277 and 278 , which have been inadvertently computed from the erroneous formula , are for the most part incorrect . mmmmmmmm Page 347 , line 16 , For crest , read crust . 348 , line 10 , supply a comma after'* upon it , " 'and omit one after\#171 ; 'covers it . " 361 , line 3 , for\#171 ; ' those , " read " of those . " ib. line 7 , for/ ' the length , " read\#171 ; a length . " 365 , line r 2 , for " particular/ 9 read " particularly " 371 , line 6 , supply a comma after " ligament , " and omit one after u cuticle . "

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ERRATA.\#x2014;PART IV.

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Measurement

ERRATA . PART IV . Page 24 , Col. Mean Chron. line 6 from bottom , for 2 15 52,44 , read 2 16 52,44 . And in Col. Mean Clock , last line , for 22 20 13,25 , read 12 . 29 1 3^5. . 31 , The second register of the State of the Barometer on the morning of the 1 8th of June , ^r Beg* , read End*. . 73 , line 12 , for increasing , read increasing..-106 , opposite April 14th , insert A. M. 126 , line 11y for Appendix , read Appendices\#171 ; 127 , wherever the word axis occurs , read axes . 151 , Col. reading of North End of needle , line 18 from bottom , erase the sign 189 , line 10 from bottom , after figures 3 , 4 , and 5 , w^ Plate YL.ai 209 , lines 6 and 7 from bottom , / or Tables VUL to XL read VII . to XII .

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Account of experiments made with an invariable pendulum at the Royal Observatory at Greenwich, and at Port Bowen, on the eastern side of Prince Regent's Inlet

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Henry Foster

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Astronomy

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Astronomy

extensive water course , and a low flat beach extending a quarter of a mile , and interrupting the high table land for the whole of that space . The land on the north side of the harbour from the head of the Port to Stony Island ( which lies about of a mile to the S. E. of the observatory ) , is similar in character to that already described on the south . From Stony Island to the north point of entrance , the coast land is not above 200 feet high , but rises to the height of 900 feet at a little distance in the interior . The house was placed with its length at right angles to the meridian , and divided into two apartments ; one was 10 feet square ; the other was five feet wide , 10 feet long , and 10 feet high . For conducting the various observations in the winter , the former of these was lined with a thick woollen cloth called fearnought ; the floor boarded , and a stove placed in it ; the latter , being for the use of the transit instrument , had a slit 18 inches wide cut through the walls and roof , and a large stone placed on the top of a cask filled with sand , formed the pedestal for the instrument . Previous to the commencement of the experiments with the pendulum , it became necessary to remove the boarded floor , and block up the door opening into the room from the outside : the entrance now being through the slit into the transit room ; the door in the middle of the partition between the rooms was protected by screens of canvas and fearnought on each side . The surface of the ground was then cleared away to as great a depth as possible , and large flat stones filled in with sand , formed the foundation for the supports of the pendulum and clock : care was also taken , that each support should stand on separate and unconnected stones % additional solidity was given to the supports , by attaching to the hindmost leg of each , a mass of lead , weighing from 40 to 50 lbs. The clock was now fixed to its support ; but the pendulum of experiment remained on board the Hecla , until all the necessary preparations were completed . The small telescope containing the diaphragm , and used to observe the coincidences , was placed at the proper distance ( 9 % feet ) from the pendulum , on its stand outside of the room , in a porch originally erected for the use of the repeating circle : this stand was sunk so far into the ground , as to bring the object-end of the telescope , on a level with the bob of the pendulum of the clock . An aperture of a foot square was found sufficiently large for observing the coincidences , as well as the face of the clock , when sitting at the telescope , which was sheltered by a screen of canvas from any rush of air into the room , on opening the door of the porch . A transit instrument made by Dollond , of thirty inches focal length , and two inches aperture , was cemented to the pedestal already described , with plaister of Paris , at the latter end of October , and brought accurately into the meridian by the transits of high and low stars . A mark was then set up at the distance of 506 feet , to which it was afterwards always adjusted before making an observation : towards the end of March , the sun 's rays caused such an apparent wavering of the meridian mark , as to render its removal necessary , and it was accordingly transferred from the exposed situation where it stood at first , to . the opposite side of the harbour , a distance of 6697 feet , where , being fixed in a hollow part of the rock , and completely shaded from the sun , it ever afterwards afforded the means of adjusting the instrument in a satisfactory manner , being perfectly steady and distinct . The allowance made for expansion , not being the result of experiments actually made on this particular pendulum , but from the deductions resulting from Captain Kater ' s experiments on a bar exactly similar , it became important in order to render the experiment strictly comparable with that at Greenwich , to keep the temperature of the room as near as possible to the one in which the previous experiments had been performed in England , namely , 50o . From the smallness of the room it was soon found , that the stove placed within it , produced incessant fluctuations in the temperature ; it was therefore removed outside , to about six feet from the north wall of the house , and sunk into the ground level with the foundation of the observatory ; built round with stones , and a tent was pitched over it . The room was now warmed by the smoke-pipe passing through it ; and , to preserve the temperature of the pendulum more uniform , a large triangular covering of fearnought lined with racoon skins , was made to enclose the whole apparatus , except that part of the front required for observation . These arrangements effected the object so far , that the temperature of the room was seldom more than 30 , and frequently not one from 50o during the observations . By a Sixes ' self-registering thermometer , the mean range of temperature to which the pendulum was exposed in 24 hours was only 8 ' , and the extreme not more than 12o during the series in June , whilst that of the atmosphere , varied from 23o to 47 ' of Fah . without any uniformity . Under these circumstances the pendulum of experiment was placed in theY'son the 29th of May , 1825 , and the adjustments finally completed on the ist of June ; the clock put in motion , and the apparatus for measuring the arc of vibration fixed in its place ; the barometer and thermometer were also suspended after the manner described in the experiments at Greenwich . The perfect stability of the point of suspension being of the utmost consequence , spirit levels were arranged on the top of the pendulum frame and clock case , to indicate any giving way in the foundation of their respective supports from the effects of thaw , which at this time very generally prevailed ; the foundations however remained solid , and the adjustments were preserved , during the whole course of these experiments , which were not commenced to any good purpose before the 14th of June , owing to an unfavourable change in the weather . This took place on the 7th of June , and was such , as rarely to permit a sight of the sun , and not one glimpse of the stars during the above interval from the 7th to 14th . In ascertaining the rate of the clock , I was confined to the transits of the sun at noon ; of Arcturus and cc Lyrae when passing south of the zenith . The sun 's transit at midnight could not be taken , in consequence of the undulations of his limb , caused by being too near the top of the high land in that direction ; neither could a Lyrae be seen soon after noon , from the general hazy state of the atmosphere at the elevation of 22 degrees . At the time of the sun 's transit his rays were prevented from touching any part of the instrument , by a screen of canvas placed between the object-glass of the telescope and the slit in the roof of the house ; it had a small hole , through which the observation was made , but being always covered except at the moment of noon , I had reason to believe that none of the adjustments were ever disturbed . In observing the times of transit , a steady going chronometer made by Henry Frodsham was used , and was found particularly convenient from its beating half seconds . A comparison between the clock and chronometer , was always taken before and after the passage of either sun or star . The time of transits shown by the face of the clock , was then deduced by direct proportion . All the comparisons are given in a separate table . It occasionally happened , owing to the state of the weather , that one of the stars was partially obscured at the time of its passing the meridian , so as to limit the observation to one or two wires only , whilst the transit of the other , over the whole five was obtained ; in such cases the mean of the rates for the clock has been deduced , by giving a value to each , in the ratio of the number of wires observed . In the observation of the coincidences , the same mode was followed as in the experiments at Greenwich . The temperature of the pendulum , however , was more frequently taken by means of a small telescope , placed outside of the room , at a window to the south , and on the same level with the thermometer , suspended a little below the middle of the pendulum for that purpose . The weather on the whole was favourable during this series ; it became somewhat unsettled toward the close ; but as no day passed without at least one transit for the rate of the clock , I had no reason to be dissatisfied with any of the observations taken . A second series was made in July , under more favourable circumstances of weather , the results of which , differ only one-tenth of a vibration in 24 hours from those in June . The total number of factors for the first series being 275,5 , and for the second 66 , a mean in that ratio has finally been taken . The experiment marked III . was made at the Royal Observatory at Greenwich in November , 1825 , after the return of the Expedition . The number of vibrations in 24 hours , deduced from this experiment , differing more than was likely to arise from errors in observation , being 0,24 of a vibration in excess of the number obtained before leaving England in 1824 , I thought it right to repeat the experiment , especially as the rate of the clock appeared to be somewhat unsteady . The results of this repetition , made with the rate of the clock more uniform , being precisely the same , I have not considered it necessary to give them in detail . The difference alluded to in the number of vibrations of the pendulum in 24 hours , being on that side which would arise from the effects of wear of the knife edge of the pendulum , and which seemed probable , from the fine metallic line distinguishable on the agate planes after its removal , I feel disposed to adopt this explanation ; and assuming an equable wear , I have taken the mean of the first and last series , as the actual number of vibrations made at Greenwich , to compare with those at Port Bo wen , which being intermediate , of course required no correction on that account . The results of this comparison are given in a subsequent page preceding the third set of experiments . It will therefore be sufficient to state here , that the ellipticity of the earth deduced from these experiments , appears to be ^9 , ^ The experiments above described are of a nature to require , at every stage , the utmost degree of care ; since an error , very small in apparent amount , either in the observations themselves , or in the subsequent computations , may prove fatal to that minute accuracy , without a due attention to which the nice objects of this problem might easily elude our notice . It will readily be understood , therefore , by every one conversant with such undertakings , that the observer , besides possessing adequate leisure , must be duly assisted in all parts of his progress by those persons with whom he is associated . And as it has been my good fortune to meet not only with the heartiest encouragement , but also the most efficient cooperation from the Commander of the Expedition , throughout the whole course of these and various other delicate researches , I feel it my duty not less on public grounds , than as a matter of private respect and gratitude , to make this acknowledgment of the source , to which every thing that may appear valuable in these enquiries is justly to be traced . HENRY FOSTER . Britain ; from which it appears that the height of the theodolite above the level of the sea was 214 feet . Theodolite above the floor of the transit room = 38 Floor of transit room above the level of the sea =176 Ball of pendulum above floor of transit room = 5\#177 ; Ball of pendulum above the level of the sea = 18I7 From the nature of the eminence , however , on which the pendulum stood , I have taken ^ of the correction so obtained , as the proper correction due to this elevation . PHILOSOPHICAL TRANSACTIONS . I. Account of experiments made with an invariable pendulum at the Royal Observatory at Greenwich , and at Port Bowen , on the eastern side of Prince Regent9 s Inlet . By Lieutenant Henry Foster , R. JV . F. R. S. Read April 6 , 1826 . The determination of the length of the seconds ' pendulum in different latitudes , is a subject , that has long been considered of much interest and importance , but more especially of late years , since the practical problem has received from the ingenuity of Captain Henry Kater , certain improvements and simplifications , which have rendered its results more accurate than had ever before been obtained . With the nature of these improvements I had already become acquainted when in H. M. S. Conway , with Captain Basil Hall , on the South American station , where , as will be seen in the Philosophical Transactions for 1823 , several series of experiments were made by that officer and myself . Soon after my appointment to the N. W. Expedition under the command of Captain W. E. Parry , the Board of 'Longitude , at the suggestion of Captain Kater , did me the honour Table I. ( First Series . ) Time by the Clock of Transits of Stars at Port Bowen , Prince Regent 's Inlet , June 1825 . Stars . 14th . 16th . 18th . 19th . 20th . 22a . 23d . h. m. s. h. m. s , h. m , s. h , m , s. h. m , s. li . m. s\#187 ; h , m. s. Arcturus 8 827,51 8 541,67 8o 9,52 75723,66 Arcturus za Sc 3d wires . , 8 16 33,03 88 13,71 85 27,95 7 59 55,92 7 57 9,94 Arcturus 3d wire 8 22 19,38 8 16 46,79 88 27,22 85 41,46 8 00 9,56 7 57 23,70 Arcturus 3d , 4th , 5th w. 82246,90 8 854,91 86 8,98 80036,91 7 57 5**05 Arcturus 5th wire 8 23 14,42 8 12 8,93 89 22,26 86 36,5 81 4,35 7 58 18,24 a Lyrae .,.12 45 9,33 \#171 ; 34 4 > Q2 12 31 17 > 73 I2 28 3X > 32 I2 22 S9 > l6 I2 22 59 > l6 Table II . Transits of the Sun . Time by Clock at the moment of Mean Noon . 15th . 17th . 18th . 19th . 21st . zzd . 23d . h. m s , h , m. s. h , m , s , h. m , s. h , m. s , h. m. s. h. m , s , II 47 41,29 II 50 00,78 II 51 10,52 II 52 20,07 II 54 39,86 II 55 49,45 II 56 59,66 From these two Tables , which are formed from the Transit Table , the following rates for the clock , contained in Tables III . and IV . have been computed . Those in Table III . by dividing the difference between the times of transit of each star , on the successive days as given in Table L by the interval in days , substracting the quotient from 3m 55s.9i , the acceleration in one day , and applying a correction to the remainder , for the change in M of each star during the interval of their respective successive transits , to obtain the rate in a sidereal day . Those in Table IV . by comparing the time by the clock at the moment of mean noon of each day , as shown in Table II . with that on each succeeding day , and dividing the difference by the number of days in the interval , by which the rate in a mean solar day for si separate intervals has been obtained . to entrust me with an invariable pendulum ; and , the details of the observations made with this instrument , together with a statement of all the attendant circumstances , are given m the following pages . The first set of experiments , which are marked ( No. I. ) , were made at the Royal Observatory at Greenwich , in an apartment to the S. W. of the Transit Room , originally intended , I believe , for the observations of the eclipses of Jupiter 's satellites , but upon this occasion kindly appropriated by Mr. Pond to my use . This room has a solid stone floor , on which the triangular supports for the pendulum and dock were placed . The roof is low , and being composed of wooden panels , the temperature of the room was materially affected by the state of the weather ; on* one occasion the thermometer ranged four degrees during the observations , although the light was admitted by a window on the north side . In the adjustments of the instruments employed in the ; experiments , I strictly adhered to the mode described by Captain Kater , in his paper read before the Royal Society in June , 1819 . The intervals between the coincidences were determined by the disappearance of the white disk on the pendulum of the clock behind the tail-piece of the pendulum , and also by the mean of its disappearance and re-appearance^ I was induced to take this additional trouble , m order to remove all possible objections which might be raise\#271 ; as to the accuracy of the result ; and partly that I might , by actual trials , furnish materials for putting at rest the controversy on this subject . The method of disappearances has been followed by Captain Kater , and more lately by Captain Basil . mean number of vibrations in 24 hours is 86223,659 by the observation of disappearance , and 86223,800 by the mean of disappearance and re-appearance . The mean height of the barometer was 29,844 inches , and the mean temp , 50o . 15 ; whence it appears that the specific gravity of the pendulum was to that of air , as 7000,6 to 1 , which gives 6v.i58 as a correction additive for the buoyancy of the atmosphere . The ball of the pendulum was found by levelling to be 121,04 feet above low water ( neap tides ) , the correction for which by the duplicate ratio of distances from the earth 's centre ( 3950,858 miles ) is , oT.5oo in 24 hours . And as the station was the tabular surface of a bed of secondary limestone , I suppose the proper multiplier is -\#163 ; \#163 ; S , which will give o'33o for the correction to be added due to this elevation . These corrections being applied to the number of vibrations before found , will give the number of vibrations that would have been made by the pendulum in a mean solar day , in vacuo at the level of the sea , the temperature being 5OP of Fahrenheit at Port Bowen , in latitude* 73o 13 ' 39".4 N , longitude 88 ' 54 ' 48 " W , and are as follows : By the observation of disappearance 86230,147 By the mean of disappearance and re-appear . 86230,288 The state of the ice in the offing being such , as to indicate no immediate prospect of the ships leaving Port Bowen , I gladly availed myself of Captain Parry 's permission to pursue these observations by another series ; the difference between the results of which , and those of the first series , being only 0.105 of a vibration in 24 hours , affords , it is presumed , . The elements of the observations for the latitude , and longitude , are given in the Appendix to the Narrative of Captain Parry 's Third Voyage for the Discovery of a NorthWest Passage . Hall and General Sir Thomas Brisbane ; that of taking a mean between the disappearance and re-appearance of the disk , has been practised by Mr. Goldingham at Madras , and by Captain Sabine . Theoretically , the mean of the disappearance and re-appearance , would give the true moment at which the two pendulums coincided at the lowest part of the arc of vibration , were it the object of this problem to determine that moment : but it is not:the experiment being strictly comparative ; and the method of disappearances accomplishes all that is sought after , with perfect certainty , and with less than half the trouble . It may , however , be useful to know , that both methods give identically the same results ; that is to say , the number of vibrations of a pendulum determined by the method of disappearance at one station , compared with the number deduced by the same method at another , give precisely the same acceleration or retardation as that which would result from comparing the number of vibrations at the first station , ascertained by taking the mean of disappearance and re-appearance , with those of the second station , ascertained by the same method . The results of the experiment contained in the following paper show this very obviously , as follows : Vibrations by the method of disapVibrations by the method of mean of pearance alone at disappearance and re-appearance at Greenwich , ... ... 86159,368 Greenwich , 86159,500 Port Bowen , ... . 86230,172 Port Bowen , ... . 86230,313 Accelerationbythemethod }_ Acceleration by the mean ? of disappearance. . > -7^\#171 ; ^ . _ of disappearance and [ -=70,813 re-appearance ... ) Table VII . ( sind Series . ) By the Sun . Computed vibrations of the Jj |JS Correct number of vibrations 1\#8222 ; . July , Julir 1825 . 182* , pendulum in 24 h. the clock\#171 ; g\#161 ; ^^ made by the pendulum in aS^ g\#187 ; \#8222 ; . Julir July , 182* , 1825 . gaining 69-.8B ( assumed\#171 ; ~ o ' ^ mean by solar day pendulum at tempea -g ^ g\#187 ; 2 rate ) in a mean solar day . gV OT S\#171 ; 5 rature oO < > . S -S | 1 . 1* III I1* From To Disappearance . Mean of Disap jS.* Sg -g Disappearance . Mean of Disap.\#191 ; \#191 ; 2 and Re-ap . O -2\#191 ; '-3 co and Re-ap . ^ s. vib . 6th , P.M. 8th , A.M. 86223,406 86223,555 7'-22 +0,340 86223,746 86223,895 224 9th 86223,436 86223,585 70.16 + 0,280 86223,716 86223,865 236 10th 86223,485 86223,6347020+0,320 86223,805 86223,954 24 8 8th , P.M. 9th , A.M. 86223,515 86223,667 70.04 +0,160 86223,675 86223,827 212 . 10th 86223,561 86223,725 70.18 +0*300 86223,861 86224,025 224 9th , P.M. 10th , A.M.,86223,620 86223,769 70.33 +0,450 86224,070 86224,219 212 Mean . 86223,812 86223,964^^26 In this series , the number of vibrations made by the pendulum in 24 hours of mean solar time , as obtained from the observations of the disappearance of the white disk , and employing the rates furnished by the transits of stars , is 86223,803 , and by the rates , from the sun 's transits 86223,812 . By the mean of the observations of the disappearance and re-appearance of the disk , the number of vibrations is 86223,938 by the rates , from the stars ' transits , and 86223,964 by the transits of the sun . But the sum of the factors for the stars being 40 , and for the sun 26 , the mean number of vibrations in 24 hours , by the observation of the disappearance of the white disk is 86223,806 , and by the mean of its disappearance and reappearance 86223,948 . If to each of these , we apply the corrections , oy,33o for elevation , and 6v , n6 for the buoyancy of the atmosphere , at the mean pressure 29,781 inches , and temperature 5i',25 of Fahrenheit , we shall arrive at the total number of vibrations which would have been made by the pendulum in a mean solar day , the temperature being 50o of Fahrenheit , in vacuo , at the level of the sea at Port Bowen ; and are By the observation of disappearance 86230,252 By the mean of disappearance and re-appearance 86230,394 By the first series , the total number of vibrations of the pendulum in 24 hours was By the observation of disappearance 86230,147 By the mean of disappearance and re-appearance 86230,288 The sums of the factors , however , being 275,5 in this series , and only 66 in the second , we obtain for the final number of vibrations at Port Bowen , By the method of disappearance 86230,172 By the mean of disappearance and re-app . 86230,313 . From the above data and number of vibrations made by the same pendulum from the mean of both series at Greenwich , viz* by the method of disappearance 86159,368 and by mean of disappearance and re-app . 86159,500 , together with the assumed length , of the seconds ' pendulum at Greenwich 39,13911 inches ; the length of the seconds ' pendulum at Port Bowen is found to be nearly 39,203464 inches , by the method of disappearance , and by the mean of disappearance and re-appearance 39,203472 inches ; and comparing these with 39,1 39 11 inches , the assumed length in lat. 51o 28 ' 39 " N. as before stated , the diminution of gravity from the pole to the equator will be by the method of disappearance,0054152 , the ellipticity of the earth\#191 ; 35 , and the length of the equatorial pendulum 39,009805 inches ; and by the mean of disappearance and re-appearance , the diminution of gravity from the pole to the equator will be,0054159 , the ellipticity of the earth 55535- , and the length of the equatorial pendulum 39,009789 inches of Sir George Schuckburgh 's scale . The length of the pendulum vibrating seconds , not having been determined at Greenwich , but at Mr. Browne 's house in London , it must be remembered that the above lengths are not the true lengths of the pendulum , but are merely given for the sake of comparison . The difference of the results amounts only to 9 ten-thousandths of a vibration in 24 hours . This , it may be observed , is the end and object of the problem ; which , as I have before stated , is strictly a comparative one ; and the only thing to be insisted upon is , that the same method should be followed , and the same adjustments of the apparatus strictly adhered to , at all the stations which are to be compared together . Supposing , however , that the vibrations recorded in the present experiments , ascertained by the one method , were compared with those determined by the other , the results would differ only 0,14 of a vibration in 24 hours ; a quantity which does not occasion a difference of two ten-thousandths of an inch in the length of the deduced seconds ' pendulum , nor of an unit in the denominator of the fraction expressing the ellipticity . There are cases , of course , dependant on the relative diameter of the white disk , to that of the tail-piece of the pendulum , in which a greater or less difference than the above would exist between the two methods so compared ; but this is of no importance whatever , as the object of the problem is fully accomplished by adhering to the same method , whichever it be , at both stations , as before stated . It may not be useless to mention also , that Captain Kater did not adopt the method of disappearances in his comparative experiments , until after innumerable trials of other plans , including that of taking the mean of disappearance and re-appearance of the white disk ; all of which he eventually abandoned for that of disappearances alone ; and it is certainly to be regretted , that he did not publish an account of these unsucBy this experiment , it appears that the final number of vibrations which would have been made by the pendulum at Greenwich in 24 mean solar hours at the level of the sea , in vacuo , and at the temperature of 50o of Fahrenheit , by the method of disapp . of the white disk is 86159,487 and by the mean of its disapp . and re-app . 86159,621 But from the final results deduced from the experiment made at Greenwich in April 1824 , previous to leaving England , the total number of vibrations which would have been made by the same pendulum under the above circumstances , by the method of disappearance , was 86159,250 and by the mean of disapp . and re-app . 86159,380 Having already stated , what I have considered to be the cause of the difference in the number of vibrations of the pendulum in these experiments ; the following arithmetical means of the results of the series in April 1824 , and November 1825 , are to be considered as the proper number of vibrations of the pendulum , at Greenwich , to be compared with those obtained at Port Bo wen , and are by the method of disappearance of the white disk 86159,368\#163 ; nd by the mean of its disapp . and re-app . 86159,500 . cessful trials , as it might have saved myself and others , much unnecessary labour . The clock used in these experiments was fitted with a gridiron pendulum , vibrating on knife edges in portions of hollow cylinders of agate , and belonged to the Royal Society . It was put in motion at Greenwich on the 17th of April , 1 824 , three days previous to the commencement of the experiment , and its rate ascertained by comparisons with the transit clock of the observatory each day at noon , and also during the series , at the commencement and at the conclusion . In these essential observations , I was kindly assisted by Mr. T. Taylor , jun . of the Royal Observatory . In making the observation of the coincidences , the following mode was pursued . The pendulum being placed in the Y 's , was gently lowered until the knife edges rested on the agate planes ; and the sides of the diaphragm placed in the focus of the eye-piece of the small telescope , were made just to coincide with , or embrace those of the tail-piece of the pendulum ; and this adjustment was examined previous to every observation . The heights of the barometer , and of the thermometer suspended with its bulb about f of the length of the pendulum below its point of suspension , and about ^ of an inch in front of the middle of the bar , were taken and registered at the beginning and end of each set of observations . The pendulum was set in motion , by drawing it gently on one side with a piece of twine fastened to one of the legs of its support , until the point at the end of the tail-piece , was about i',2 upon the arc ; and a little before the pendulum of the clock attained its highest ascent on that side , the twine was let go , and the pendulum allowed to vibrate freely . The number of vibrations made by the pendulum in 24 hours reduced to the level of the sea , in vacuo and at a determinate temperature , were computed by the methods detailed in Captain Kater ' s paper before referred to . The second experiment marked ( No. II . ) was made at Port Bowen , on the eastern side of Prince Regent 's Inlet , where the ships passed the winter of 1824-25 . The observatory house , prepared in frame at Deptford , having double walls and roofs , three inches apart , was erected early in October on the north side of the harbour , upwards of a hundred feet above the level of the sea , on a bed of secondary limestone , of which this place is composed ; the upper stratum consisted of small loose stones , that could only be removed to the depth of a few inches , below which , it was frozen so hard , that little impression could be made by the action of crows and pickaxes . The high table land , which characterises this coast , rises directly from the sea , on the south side of the harbour , to the height of between six and seven hundred feet ; the upper part , presents a perpendicular cliff of one or two hundred feet , exhibiting alternate black and white horizontal stratifications of secondary limestone ; it is also deeply excavated in a variety of places by the action of the weather on its less durable parts , thus giving to its outline the appearance of ruined towers and other ancient edifices . The debris , which has fallen from the upper part of the rock , has formed a steep shelving bank or " talus " along its base , except at those places where its outline is intersected by ravines , and here , projecting points are formed of the materials brought down by the melting of the winter 's snow . To the eastward , at the head of Port Bowen , there is an

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Observations on the diurnal variation of the magnetic needle, at the Whale Fish Islands, Davis's Strait

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Henry Foster

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Observations on the diurnal variation of the / magnetic needle , at the Whale Fish Islands , Davis9 s Strait . By Lieutenant Henry Foster , R. N. F. R. S. Jlrevious to leaving England in the spring of 1824 , 1 had determined upon making a series of observations on the daily variation of the magnetic needle , during our stay , at the different places which might be visited by the Expedition . Accordingly , soon after our arrival at the Whale Fish Islands , for the purpose of transhipping the stores from the Transport which had accompanied us thus far ; the instrument for observing the diurnal variation was landed , and placed on a pedestal in a small octagonal observatory . The length of the needle was 11 inches , and weighed 120 grains ; it rested on a pivot ; and its direction when the sun was on the magnetic meridian I assumed , for distinction 's sake , the zero of my scale . The observations were continued for three days only ; and as the brass work of the instrument was afterwards found to be magnetic , the results obtained are , of course , too doubtful to be considered of any great value taken singly ; but as it was these observations which first indicated to me the agency of the sun , in producing the interesting phenomenon of the daily variation , I have thought it right to give them in detail , together with such remarks as occurred to me at this early stage of the enquiry , as preliminary to the more extended and exact observations made at Port Bowen by Captain Parry , the other Officers of the Expedition , and myself , an account of which accompanies this communication to the Royal Society .

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Magnetical Observations at Port Bowen,\c. A.D. 1824-25, comprehending observations on the diurnal variation and diurnal intensity of the horizontal needle; also on the Dip of the magnetic needle at Woolwich, and at different stations, within the Arctic circle

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Philosophical Transactions of the Royal Society of London

W. E. Parry|Henry Foster

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The needles , distinguished by Nos. i and 2 in the following tables were suspended , instead of supported , and were contained within a small wooden box having a glass cover . The centre of each was made exactly to coincide with the centre of motion of the index of a common Hadley 's quadrant , graduated to minutes as usual , the box being fixed upon the index and moving with it . The agate cup of each needle was just allowed to touch a fine steel point of support , in order to preserve their correct centres . No. 1 needle belonged to an azimuth compass on Capt , Kater 's construction , its lozenge shape being that figured in the Appendix to the Voyage of 1819^20 , p. cix ; except that this needle was rounded at the corners forming the extremities of its transverse diameter . Its weight ( with the addition of mica ends increasing its length to eight inches for the purpose of more accurate observation ) was 104 grains , that of the needle alone being 50 grains . No. 2 needle was formed of clock spring , and furnished by Mr. Christie , for some experiments to be made with it under the influence of magnets . Its shape has been already described by that gentleman in his paper on this subject , in the Philosophical Transactions for the year 1823 . The length of this needle was 4,9 inches , but increased by mica ends to about ten inches , in which state it weighed 96 grains , that of the needle alone being 51 grains . Both these needles were delicately suspended by a few fine threads of floss silk , from seven to eight inches in length , having no torsion , and passing up through a copper cylinder over a small brass pulley . A leaden weight just equivalent to that of the needle was then attached to the other end of the silk , in order to adjust it so that it might barely touch the centre or point of support . No. 3 needle , which was that of a common ship 's azimuth compass , and weighed 146 grains , was suspended like the other two , but simply contained within an air-tight box having glass ends . A sight of card paper being fixed towards each extremity of the needle , the amount of variation was obtained , by observing the coincidence of the sights through a small telescope traversing upon an arc of ten fee radius , and consequently placed at that distance from the needle . A vernier attached to the telescope , and moving with it , gave the reading to the nearest minute . This needle was afterwards used exclusively for obtaining the changes in the magnetic intensity , for which it was found remarkably well adapted ; the instant of the coincidence of the two sights being easily observable through the telescope to two-tenths of a second , by means of a chronometer held to the ear . During the absence of daylight , these observations were made by candlelight , transmitted through a sheet of oiled paper , fixed against the glass end of the box , farthest from the observer . The observations were made at the commencement by Lieutenant Foster and Captain Parry , but were subsequently carried on in regular watches , and the needles visited every hour during four successive months , by Lieutenants Sherer and Ross , and Messieurs Crozier , Richards and Head . When any extraordinary change , however , appeared to be going on , the needles were more closely watched ; and every phenomenon , such as the aurora borealis , meteors , clouds , the kind and degree of light , the moon 's position , and the temperature within and without , were at all times carefully noted . In the following tables these phenomena , with the exception of the temperature , have necessarily been omitted , on account of the great length to which their insertion would have extended this communication ; but an abstract of all the particulars relative to one of the needles , No. 2 , has been made by Lieutenant Foster , and is given in continuation of this series ; diagrams exhibiting graphically the various deflections of needle No. 1 , for which we are indebted to the ingenuity of Mr. Hooper , are also subjoined . The original register of the whole is preserved and can easily be referred to , should any of the observed phenomena , beyond those which are here given , be considered likely to have influenced the motion of the needles . As far , however , as our own observations extended , we have reason to believe that on no occasion were the needles in the slightest degree affected , either by the aurora , meteors , or any other perceptible atmospheric phenomenon . Soon after the observations were commenced , it was ascertained that twice in every four and twenty hours the needles moved past a certain point , which may be denominated the zero , or mean magnetic meridian ; a fact , which was first rendered clearly apparent , from the accompanying diagrams already mentioned , by which it appears that in every instance.except one , both needles every day passed the line in question . On a single day , February 24 , the needle No. 2 did not arrive at it during its eastern motion . The means of the times of the needle passing this zero , as deduced from four months continued observations , is , 6hi$m A. M. , and 4h 37m P. M. ; the mean time in each month being as follows : 1825 A. M. P. M. January 6hoora 4hoora February 6 304 00 March 5 so -50 ' April 7 00 -5 so Mean 6 15 4 37 To avoid the insertion of many useless figures in the tables , the resulting amount of easterly or westerly deflection on each side of the zero has been computed . The maximum westerly variation at Port Bowen appears , from these observations , generally to have occurred between the hours of ioh A. M. and ih P. M. , the mean result of one hundred and twenty days ' observations being nh49ra A.M. The minimum westerly variation , or the greatest deflection of the north end of the needle to the eastward , took place between 8h P. M. and 2h A. M. , the mean time , deduced as above , being ioh im P. M. In a few instances the maximum deflection of the needle to the westward occurred as early as 8h A. M. , and as late as 3h P. M. ; and in like manner , the greatest deflection eastward took place at 2h and sh P. M. , on some few occasions . In all these anomalous cases , however , it was remarked , from simultaneous observations on the times of vibration of a suspended horizontal needle , that these irregularities were evidently due to an extraordinary alteration in its intensity , which produced a deflection contrary to the regular order of the motion of the needle . The diurnal change of direction appears , by these observations , to have been seldom less than one degree , and sometimes to have amounted to 5 , 6 , and even 7 degrees , and there can be no doubt that the changes in this amount were

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Abstract of the daily variation of the magnetic needle No. 2

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Foster

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IV . Abstract of the daily variation of the magnetic needle No. 2 , by Lieut. Foster . In the following : tables are given the times of maximum and minimum diurnal variation , together with the instrumental range and value in arc of such daily change . In an adjoining column are placed indications of the relative position of the moon with respect to the sun ; as there seems some reason to think that these bodies have each its influence on the needle : at all events it will be seen , that in every case the daily variation was always greater when the southern declination of the moon was greatest , and commonly a minimum when her declination was increasing to the northward.* The action of the sun , however , was much less equivocal , and its increasing effect on the daily variation was rendered very manifest as he advanced to the nortnward . With a view to placing in evidence the proportional part of the annual variation due to each month , the mean of the maximum west and east expressions , has been assumed as the daily zero , or magnetic meridian ; but on reference to the column containing it , there appears such irregularities in its directions , as to render any -conclusions drawn from it , very unsatisfactory . Abstract of the Results given in the preceding Table of Intensities . The following Table is an abstract of the preceding observations on the diurnal change of intensity of the horizontal magnetic needle , at Port Bowen , during the months of February , March , April , and May , in the year 1825 . The second , third , fourth , and fifth columns of this Table , have been formed by dividing the sum of the times of vibration at each hour , for every month , by the number of days , for the mean monthly intensity at each hour ; and the last column is formed by dividing the sum of all the times , by the number of days , for a general mean result . In this , however , the observations made in May are not included , in consequence of the re-magnetising of the needle , as stated at the head of the Table of that month 's observations . Monthly and general mean Intensities of the horizontal magnetic Needle for every hour . February . March . April . May . General mean Hour . Mean time in perMean time in perMean time in perMean time in perindependent forming 60 vib . forming 60 vib . forming 60 vib . forming 60 vib . of May . h. seconds . seconds . seconds . seconds . seconds . A.M. 1 1076,8 1079,1 1098,9 916,4 1086,6 2 1073,5 1083,1 1100,7 1089,4 3 lo7S > 7 1082,1 1102,7 930,7 1089,1 4 1080,7 1084,8 1102,7 1091,1 5 1082,5 1082,8 1101,7 923,2 1090,3 6 1082,1 1082,4 1105,4 1090,6 7 1082,8 1082,9 1108,2 922,6 1092,6 8 1082,9 1083,1 1109,1 1093,4 9 1080,9 1084,7 1108,1 927 > 5 1094,2 10 1079,5 1081,7 1107,1 1091,4 11 1O77 > 9 1081,9 1101,9 923,6 1089,0 Noon 12 1077,1 1077,4 IO93 > 3 1084,6 P. M. 1 IO75 > i 1062,6 1092,5 9H > 4 1081,1 2 ! 072,7 1062,6 1106,6 1084,5 3 1077,9 1076,4 1110,2 905,2 1087,6 4 IO77 > 4 io73 > 6 1090,9 1094,9 5 1073,6 1073,4 1094,0 905,4 1081,7 6 IO73 > 5 1072,1 1090,7 1086,2 7 1074,2 1072,0 1089,2 904,4 1079,1 8 1073,8 1074,0 1088,7 1079,7 9 l'75 > 1 IO74*S 1091,2 906,0 1080,8 io 1073,8 1074,8 1092,1 1081,3 n 1075,1 1075,9 1093,3 911,6 1082,3 Midnight 12 1076,3 1077,1 1096,1 1083,9 From the general mean of the above results , it appears , that the maximum intensity of the horizontal needle at Port Bowen , uniformly took place about 7h P. M. ; but the time of minimum intensity is not so well denned , although it seems to happen somewhat later in the morning .

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Observations for determining the dip of the magnetic needle

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W. E. Parry|Henry Foster

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V. Observations for determining the dip of the magnetic needle . Dip of the magnetic needle observed at Woolwich , and at different stations within the Arctic Circle . JL n the following Table , is given a general abstract of the dip of the magnetic needle , and of the magnetic intensity , observed at different stations within the Arctic Circle , in the years 1824-25 ; and of those at Woolwich , both prior , and subsequent to the voyage . The instruments employed in these observations , were those by Jones , and Dollond , already described in the Appendix to the two preceding voyages of discovery ; but on this occasion , other needles were added , the whole being numbered as follows : No. 1 . A rectangular needle , 7^ inches in length , constructed by Jones on Meyer 's principle , having a light cylindrical arm at right angles to its axis , for screwing on a small brass sphere . 2 . The same needle , with a sphere somewhat larger . 3 . The same needle , with a still larger sphere . 4 . A plain rectangular needle of the same length as the above . 5 . A needle similar to No. 4 , but used only for the intensity . 6 . A conical needle , by Dollond , ii\#177 ; inches in length , having a moveable axis , for shifting into four different positions ; used with the instrument of his construction . 7 . A plain rectangular needle , of the same length as No. 6 , and used in the same instrument ; but employed exclusively for the intensity . It may not be unnecessary to state , that every precaution which suggested itself was taken to insure accuracy , and that the needles were vibrated after each , observation , by means of a small piece of magnetised wire , that their axis might not be injured by raising them in the Y 's oft ' the agate planes . Each of the registered observations on the dip , were deduced from five readings of the needle , in each of its different positions . The observations for intensity , by means of the time in which the needles performed one hundred vibrations in the meridian , are deduced from the mean of four hundred vibrations , obtained with the face of the instrument on each side of the vertical , and the needles reversed on their axis , in the two positions .

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Observations on the diurnal changes in the position of the horizontal needle, under a reduced directive power, at Port Bowen, 1825

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Philosophical Transactions of the Royal Society of London

Henry Foster

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VL Observations on the diurnal changes in the position of the horizontal needle , under a reduced directive power , at Port Bowen , 1 825 , By Lieutenant Henry Foster , JR . N. F. R. S. Communicated January 12 , 1826 . A he daily variation of the horizontal needle is a subject which has , for nearly a century , attracted the attention of several accurate observers , whose object was principally limited to determining the hour of the day , when its amount was the greatest , and the times of the needle 's successive easterly and westerly motions . From these observations , however , it could not be ascertained whether the cause of this daily variation proceeded from an actual change in the direction of the magnetic axis of the earth , or whether it arose from some foreign force , , acting transversely on the needle , impelling it out of its natural direction . To submit this question to the test of observation , Mr. Barlow , in 1823 , undertook a set of experiments on the daily variation of a horizontal needle nearly neutralized by the application of artificial magnets ; under an idea , that if the daily variation proceeded from an actual change in the direction of the earth 's magnetism , the needle in this case , as when in its natural state , would merely take up its new direction without any increase of amount ; but if it proceeded from a foreign force acting transversely upon it , the needle now having less intensity of direction than when in its natural state , it would yield more easily to this transverse force and give a larger expression , which would serve to mark with more precision than heretofore , all the circumstances of this daily change . On trial , the amount was found to be very considerably increased ; and he , still in pursuit of the same object , now undertook to ascertain the direction which the daily variation impressed upon the needle , when balanced at different azimuths ; which was easily done by a slight adjustment of the magnets ; and in this way he found that in two positions of the needle , viz. when its north end was directed either to N i6 ' W , or S i6 ' E , no daily variation , or a very little took place , and that on one side of this line , the needle passed in one direction , and on the other side in an opposite one . In the memoir which the Author published relative to these experiments , he expresses a wish that some other persons would pursue this enquiry ; and as the parts in which we were likely to winter in the recent voyage of discovery under Captain Parry , seemed highly favourable for the purpose , I determined to avail myself of this circumstance , and to make a regular set of such observations . With respect to the daily variation , it was soon found , as was expected , that the needle being nearly neutralized by the great amount of dip , no artificial means would be necessary for increasing its amount : all the observations , therefore , on this head , were made with the needles suspended in their natural state , and the following are entirely devoted to the second object , viz. of determining the direction which the needle takes in consequence of the daily variation when directed to different points of the compass , and to ascertain the line of no daily variation , or at least that line in which the motion is a minimum . Mr. Christie , in pursuing the experiments above referred to , and in those on the effects of temperature on magnets , had made use of an instrument admirably suited to such purpose ; and he very obligingly superintended the construction of one somewhat similar for my use ; a description and drawing of which he has given in his paper on the effects of temperature on magnets , published in the Phil. Trans , for 1825 . In these experiments , the apparatus was frozen to three firm stone supports , erected in a house built of snow , having the top covered with canvas ; the zero on the compassbox was made to coincide with the direction of the needle at 6h A.M. , that being , although somewhat arbitrarily considered ( from the mean of the preceding month 's observations on the daily variation ) , the magnetic meridian . The needle used was made of clock spring , very delicate and light , in length 4,5 inches , its greatest breadth at the centre was 0,45 inches , and its extremities terminated in sharp points ; the pivot on which it rested was also repolished previous to the commencement of the observations . Having considerably reduced the directive power of this needle in its natural direction , by the action of two bar magnets , placed in the magnetic meridian , and in the same horizontal plane with it ; I began on the 14th of February to register the amount of the daily change at stated intervals throughout the twenty-four hours , the Officers of the ship kindly assisting me , by taking the observations at the times of my attendance to other duties . The states of the two thermometers placed upon the instrument , were also noted at the time of every observation ; and to preserve the intensity pf the magnets from being affected by any sudden change of temperature , produced by the approach of the observer , or other causes , they were thickly covered with snow after every adjustment . During that part of the day when the needles suspended with floss silk indicated westerly variation , the direction of this needle is marked towards the right hand , when the north end passes to the right hand of a person standing outside of the compass-box y and facing the north end of the needle ; and to the left , when it passes towards the left hand . In the following details is given a short description of the adjustment of the magnets to the needle , at the commencement of the observations in each position of its north end ; and also the time in which it performed one vibration when imder their influence , as well as the ratios in which the ditective/ force was reduced by them ; but it must be remembered , that these ratios are mere approximations , since the directive force was always so much diminished , that a sufficient nuhiber of vibrations could not be counted , to estimate the duration of one With the required exactness . In the annexed tables every phenomena , such as halos , aurora borealis , winds , sitate of the weather , and position of the moon , are inserted ; together with such remarks , as suggested themselves at the time of observation . There is also inserted in o italics in the column of remarks ; max . easterly and westerly variation , opposite the hours at which they respectively took place by the suspended needle\#327 ; o. 2 , in order to define the time of the day when the motion of this needle was toward\#171 ; the tight , or left hand , as above described . And to point out the times of maximum westerly and easterly deflections of this needle , the signs + and a*e prefixed to the hours of observation when they respectively happened . North end of Needle to the North . The magnets being placed to the north and south of the needle , with their axes coinciding with the magnetic meridian , the north magnet had its north pole , and the south magnet its south pole , directed towards the needle , at the distance of 31,5 inches from the centre of the compass-box . In this position of the magnets , the needle made one vibration in 15 seconds , so that the directive force was reduced in the ratio of 0,14 to 1 nearly . Direction of ' " ' ' ~~ Mean Time A. M. Reading of *allren p^mp't north end of Time that a hoDate ^ateofObseror north end of *allren . needle during rizontal needle WinH < WuwU Wpflfi , pr Weather* " Rpmflrlr\#171 ; Remarks , & n &c. Date ^atevation . p.m. or Needle . westerly daily took to make WinH < WuwU Wpflfi , pr Weather* " Rpmflrlr\#171 ; Remarks , & n &c. Instr . variation . 60 vibrations . 1825 . h. m. 0,0 m. s. Feb. 14th 030 A.M. N3 20 E 19 Calm Hazy Aurora faint . 100 450 19 Aurora no\#357 ; vis , 200 500 19 ' Max. easterly 2 25 5 00 19 variation . 635 500 -20 N. Fresh Ditto 6 40 4 30 20 6 45 3 40 20 700 1 30 -20 Cloudyto 7 42 North 20 the east7 52 N3 00W T20 # ward . . -d # 10 00 4 30 20. . J N. Light Clear and 10 10 5 30 20 ^ fine 11 00 8 00 20 ^n 17 8 20 20 'u 11 32 8 20 20 Jg 11 47 8 40 -20 ~ Noon 8 40 -20\#163 ; h o 32 P. M. 9 00 20 0 35 Io oo 2O NO Fresh Squally Max. westerly 0 37 > o 30 -20 variation . 0 40 10 55 20 +O 42 II OO T2O 15 XI oo ~2 ' NNW Moderate 1 23 11 00 21 2 OO II OO 2,1 2 2O II OO -2.1 2 32 IO 30 21 2 45 IO OO 21 8 10 O 2O 21 8 2O N25E -21 9 33 z 5 ' -23 IO 35 8 50 22\#191 ; 10 37 io 20 22I 1052 1040 23 Ditto Ditto Max. easterly 11 2 10 10 23 variation . 11 30 10 10 23 11 52 10 00 -23 u , m ' J S i North end of Needle to the North . At this time the magnets placed north and south of the needle , had their axes inclined to the magnetic meridian at an angle of 22 degrees , and the distance of their nearest ends from the centre of the needle was 32,95 inches . The time in which the needle now performed one vibration , was 10,24 seconds , and the directive force reduced in the ratio of 0,325 to 1 . Direction of Mean Time A. M. Reading of\#191 ; jJSa * north end of Time that a hoDate . ofObseror north end of * needle during rizontal needle w^ , , . Wmaa ' w Weather4l % PfllBW , Ifemarks . &c. .\#8222 ; vation . P.M. or Needle . ~Z westerly daily took to make Wmaa ' w^ , , . w Weather4l % Ifemarks . &c. PfllBW,.\#8222 ; Instr . variation . 60 vibrations . 1825 . h. m. o , o m. s7 " " --.-.-Apr.isth 1 20 A.M.N 2 30 E io , g 7,8 NEbyNSqually '1 SO 2 40 -10 NEbyNSqually ' h4 fow 1 50 2 40 -10 d0/ n 2 lS 200 -10 1811,8 300 N030Wio| 1811,9 4 00 1 20 11 18 10,5 5 10 4 oo n. . -a'. . 18 0,8 5 oo 4 30 -12. . g. . 18 0,4 6 50 8 20 -12.\#163 ; 6 Si 8 30 -12 e. ^. . -i7 S5 8 ' ' 9 30 -11. . 'C. . 18 2,8 949 30 -11. . JS. . 17 59 10 S 950-9.--.o. . l8 4 > 8 030 1 oo p. M. 800 -5 ... . With drift qnenuy obseryed to vi1 oo 6 30 5 ... . 17 4.7,5 brate in very amallares , 1 30 6 30 5 . uit proceeded to the 2 OO 2 IO c C* ITC\#187 ; eastward from its Mm . 2 230 ~ 210 2 IO -c > c l"S C* " ITC\#187 ; 7S\#171 ; .\#171 ; imposition ; asweU ~_ -c > f Si asm its progress again 2 4S 5OO-5 _a totheWestwAd , from2 " progress 300 5 10 5..X. . 18 1,2 Ma*.eaifcrfot > .\#187 ; 6 " P. M. It fa also 430 900 -6,.U. . 18 II Squally worth , of remark that +S 55 IO 20 8 J ... . 18 8,2\#171 ; .ntai\#8222 ; eeale was ob ' 55 9 IO 8 served to be very change\#171 ; 57 840 -8 18 7C ible , and the action of 752 825 -9 18 0,4 Lt.breeze the saspended needles 97 8OO -5 l8 0,4 8,7 fromN . 'eryaregular . 10 57 so -10 18 8,5 -"4 650 -io 1810,5 Finewea . a 6th < u ^ 1MH\#381 ; 5 ' , ~IC l8 9 > 3 Easterly Clear and Apr. , a < u 6th ^ 1-A.M.N 1MH\#381 ; 5 ' , ~IC 50W-11 . . " I |. . " 187,7 l8 39 > I 9 > 3 Easterly light7 Clear fine and Ma3c.msterl 620\#163 ; fo -9 " I " 39 > I happen\#171 ; at 2^A.M . 700 8 00 , o 10 6I s ' ... ? ^. . ! 8 30,6 8 00 10 40 6I ... . . ? ... .,8 31,2 9 15 Io 25 2. . S. . 18 52 10 10,2 00 1 ... .,8 2j,6 + ''\#187 ; 5 12 5 -1..\#163 ; . . 10 30 12 51 11 Io . 9 30 +1 i8 16,8 " 3* 9 20 +1 058 P.M. 740 +2 17 57,5 1 25 710 +4 ,8Io,8 1 30 6 30 + 4\#187 ; 57 6 10 + 4| 3 'o 3 20 +54 00 3 30 +55 'S 7 * ' + 3i 18 24,4 North end of Needle to the South . In this case , the adjustment of the magnets was the same as in the preceding observations on the 14th of February , with this exception , viz. that their ends nearest to the needle were 27 inches from the centre of the compass-box ; the needle under these circumstances making 1 vibration in 14 seconds , and the directive force reduced in the ratio of 0,154 to 1 . " " " " " " " " ^ ~ Direction of | Mean Time A. M. Reading of *ahrenIV^ ' north end of Time that a hoDate ofObseror north end of *ahrenneedle daring nzontal needle w^ Weather . Remarks , &c. vation . P.M , Needle . westerly daily took to make Instr . variation . 60 vibrations . 1825 . h. m. o ' , o m. s..\#187 ; _TT Feb.i7th 020 A.M.S520E -22 NNW.\#187 ; _Hazy TT 0 45 S 40 -22 Light weather 100 540 22 17 52*5 ... . . Max. easterly _ . 'variation . 4 4 ' 5 4 ' " 22 X7 56 > 4 . 5 50 5 40 23h 6 15 5 40 -23 17 59,5 7 40 5 4 ' ~22 *7 55 9 00 5 40 -22 17 54,3 9 37 5 3 ' 2ll Calm Hazy 10 75 30 zi } 17 52 weather 10 30 5 30 -21 11 10 5 30 -21 11 20 5 20 21 J. . -d ... 17 50,5 Noon . 3 40 -21 1. . U. . 18 1 North 0 45 P M. 3 2O -2l ... 5. . 17 57*8 Light 1 20 3 00 -21 ^1 30 a 00 21 jg 1 40 o 50 -21 ** 1 45 o 40 -20 eh 200 0-20 -20 17 5^7 Max. westerly 2 12 Sout'Tr -2O variation . 2 30 So 20 W 20 * 45 04 ' -20 Hazy to +3 oo l ' ' 2O 17 5O > 8 North Fresh theeastward 35 1 00 20 Clearover 3 20 1 00 20 head and 4 12 o 50 -20 17 47,2 to the 6 00 040 -21 17 51,4 westward 7 35 o 40 21J 17 50 810 S1 40 E -22 Aurora faint 830 230 21J Hazy totheN . E. 9 00 2 50 2i| by compass\#187 ; 9 3 ' 3 00 -22 Aurora not 9 5 ' 4\#187 ; o 22 visible at 10 00 6 00 22 17 47,3 8.30 . 10 10 6 20 -22 10 30 6 20 -22 11 00 6 20 22 ... ... . . I7 5O xx 30 6 40 22 Midn1 640 22 17 52,5 North end of Needle to the East . The axes of the magnets placed north and south of the needle , were on this occasion inclined to the magnetic meridian at an angle of 22 degrees ; the distance of the nearest ends of each , from the centre of the compass-box was 28 inches , and the time of performing one vibration by the needle was 16,4 seconds , so that the directive power now , was to the undiminished force as 0,113 to 1 . < .Direction of Mean j^ -^ ' Reading of Temp. north eu d of Time that a hoDate . ^meof Or ' north end of Fahren* , needle during rizontal needle make Windg Weatner . Remarks , &c. Obserp^ * jyj * Needle . westerly daity took to make vation . ** Instr . variation . 60 vibrations . 1825 . h. m. o/ o m. s. Feb23rd . 1 00 A. M.E 1 00 N 26 17 57,2 Eastward Clear I 55 E2 OO S 27 ... ... ... 18 3,6 Max. easterly var . 300 1000 -27 ... ... ; . . 18 5,2 Aurorabright 415 800 -27 ... . . ; ... 18 2,6 tothenorth ; 5 30 7 30 -27 A ... . . 18 3,4 at 4hbrilliaiit 600 730 -27 18 9,5 from NW to 6 40 7 30 -27 NEby(com7 00 4 40 -26$ pass . ) 75 IOOO -2O| ... ... ... l8 1J,7 7 20 19 00 -26 7 25 18 30 -26 7 30 19 40 26 +7 32 20 00 -26 7 35 20 io -26 7 40 19 00 26 7 42 18 50 --27 . The max . westerly 88 IO OO -27 18 II , I Easterly Hazy var . happened by 8i2 9 30 -z ; ... ... ... ... ... . Fresh ILaTTIS 9IO 4 40 --27 ... ... ... 18 1,5 48ra Iiear|y . The . 9 30 5 OO 27 ' ' indications of this 9 40 O IO -27 * needle appear to IOIO 650 -26* ... . t8 2,3 be rather those of 10 40 4 30 20 since the irregu1 1 OO 4 OO -26 ... ... ... 17 59*3 larities ( by comII 30East ' paring them with 1.33 E icon _26 ... AtaT^dS " 3o O 30 26 were found to folII 40 East ' low that law . II 45 EI OO S 25 Noon 2 00 25 ... ... ... 17 59,6 East Hazy Very cold W. 0 IO P. MI 30 -25 ... ... ... Clear overO 5a East 25 ' ... ... ... Fresh head , much E3 00N -25| ... ... ... ,7 S4,5 ^'Weiy " y1 15 4 20 -25 e\#191 ; oid . y1 25 5 10 *5i 1 30 5 10 -25* 1 35 5 oo 25e 1 45 5 20 -25e 2 00 5 30 25J 17 51,3 2 10 5 20 25^ 2 30 4 00 25I 3 00 4 00 -25e 17 54 3 25 4 oo -25e 3 55 4 09 25\#381 ; 17 5i > 4 5 3 ' Soo -25 } ... ... ..17 50,1 North end of Needle to the West . What has been said of the adjustment of the magnets at the commencement of the observations at East , obtain here also ; except that the axis of each magnet in this instance , was oppositely inclined to the meridian at an angle of 22 degrees , in order to direct the north end of the needle into its present position . Direction of JTirae that a Mean A. M Readme of v Vmp ; north end of horizontal ' vation . Instr . variation . vibrations . 1825 . h. m. o/ o m. s. Feb. 26th 100 A.M. West 27 East . Hazy Max. easterly var . 2 00 W240N 27 17 55,8 strong 2 35 3 30 -27 3 00 3 30 -26 17 55,4 3 30 3 30 -26 17 56,0 3 SS 3 40 -2O 5 30 4 30 25 18 00,2 64 450 -25 17 58,1 75 4 40 -25 18 00,5 9 30 4 4 ' 25 1.8 2\#191 ; 2 1000 440 22 17 57,3 II OO 4 30 21 17 57,0 Noon 2 30 21 17 55,5 i 00 P.M. 1 40 -21 17 s$,7 1 30 1 00 -21 ES Strong 1 45 West -21 gales , 1 50 W140N -21 withdrift . 2 15 1 00 -21 17 56,5 Max. westerly var . 2 20 West 21 2 30 Wo 10 S -21 39 West -19 17 57,6 3 50 West -19 17 56,5 +S 30 Wo 15 S -18 ... ... ... 17 57,4 620 WoioN -17 17 56,8 D WNW by compass . 6 55 o 10 -17 17 $6,6 740 o ao 16 1756,9 9 30 o 30 14\#381 ; 18 00 10 00 o 30 14\#191 ; 18 00,5 ES Thick & 10 30 o 30 14\#191 ; strong hazy 11 00 030 -14* 18 1,3 Max. easterly y var . 11 30 o 30 14I y Midn* 040 -He 18.1,5 Feb. 27th o 15 A.M. i co 14^ Easterly Thick & 18 1 20 -14 18 1,5 light hazy with 25 l 30 H 18 3,7 snow 3 00 14 ' H 18 3,8 3 S ' 1 40 H 18 4,2 5 30 1 50 -14 18 3,5 6 10 1 50 14 18 2,2 6 30 1 50 i4i 7 00 1 5 ' H 18 3,2 7 55 * SS -H 18 5,0 Calm Cloudy 9 00 1 55 -14 18 4,9 North end of Needle to the West . Direction of ^ean A. M Readme of TemP* north end of Time that a hoDate . A ? pi^J^-l^^SSISAA Wind , . Weather . Be-na^fcc . vation . Instr . variation . 60 vibrations . 1825 . h. m. o/ o m. s. Feb. a8th 56 P.M. Wo 20 S 17 17 57,5 Easterly Clear and 63 05 -18 17 S7 > 3 LiSht Fine 6 55 Wo 20 N 19 17 59,6 7 00 o 30 19 7 55 ' 4 ' -19 17 59 > ' 930 040 20 17 57,2 io 00 1 00 -20 ... ..,. . 17 57,7 10 30 1 00 20 11 61 00 20 17 57,6 Ditto Overcast 11 40 1 00 20 westward Mid1 . 1 00 20 17 58,1 Marchisi i oo A.M. l oo 19J 17 59,5 1 30 1 00 19 200 1 10 18J . . 1800 Max. easterly 3 oo . 2 30 i8j\#163 ; 17 59 > 3 variation . 5 10 400 19 18 1,4 S.W. Hazy 68 430 19 18 3,3 Moderate westward 76 5 00 20 18 4,8 7 4 ' 7 5 ' -20 ... ... . . 18 8,2 9 00 7 3 ' 21 1 18 11 9 30 7 30 22 *o 15 7 30 -22 18 7,8 NO by E Thick 10 45 7 30 23 Fresh with drift *i 15 7 30 -23 18 9,5 11 45 5 30 24 ... ... ... Max. westerly Noon . 400 24 17 co , c variation . 08 P.M. West -24 +o 30 Wo 30 S 24e 1 00 o 30 24J 17 52 NO Fresh Overcast 1 30 West 24J 2 00 West _24\#163 ; 17 53,2 2 30 West 24^ 300 Wi 00N 25I 1752,8 3 30 15 ^25\#191 ; 4 4 ! 15 26 17 54,3 5 10 i 30 -26 17 55,2 North Hazy Max. easterly 6 00 2 00 26 ... ... . . 17 56 Light variation . 700 210 -26 ... . 1756,6 7 5 ' 2 Io -26 17 57,8 10 3 ' 2 00 -30 17 55,0 11 00 2 00 30 17 54,0 N. Eastey Clear and D Mag. -11 3 ' 2 20 -30 Light Fine North . Midn1 200 -30 17 55,5 It will be seen , that when the north end of the needle pointed towards the east or west , the direction of its motion during the time of westerly daily variation , is not specified according to the mode described ; I have not ventured to do so , in consequence of the many irregularities in its direction , produced by the variations of horizontal intensity , which were always indicated by this needle , and which rendered its direction as to the right and left hand during the time of westerly daily variation , very doubtful . North end of Needle to the S. W. The distance of the nearest ends of the magnets from the centre of the compass 27 inches 5 the axis of each magnet was inclined to the magnetic meridian , and the needle under their influence made one vibration in I2S seconds ; so that the directive force now , was to the undiminished force as 0,20 to 1 . ~ Direction of * . Mean A.M. Reading of '\#163 ; \#163 ; \#163 ; n north end of Time that a hoDate . *\#163 ; \#163 ; put " ^* A^Aiif\#8482 ; nd " W\#171 ; *\#187 ; .*-**\#187 ; vation . " Instr . yariation . 60 vibrations . 1825 h. m. 0,0 m. s. Mar. id i 00 A. M. S 42 00W 29 17 56,3 Northerly Clear and i 30 41 50 30 Light Fine 200 41 3 ' 29I l7 S* . 230 40 50 -30 3 20 40 20 30 17 59,1 Calm 400 3950 3'i 18 9,3\#163 ; 6 40 00 51 18 3 Easterly Clear and 68 40 20 31 ... 18 3 Light Fine 76 41 20 31 18 1,8 7 54 41 30 32 18 1 900 43 2O 32 1800,5 9 30 44 oo -^3* 10 00 4530 32 . " g. . l7 53\#187 ; 2 Max. westerly 10 30 46 10 31 rt variation . 1 100 46 20 -30. . ~. . 17 53,6 H 30 45 5 ' 3 ' JS 0 1S P.M. 45 30 3'..\#171 ; . . 18 2,2 0u 4C 30 -30 +3 0 i " u 4C 45 . ; ; 30 ^n 30 -30 -30..\#163 ; ..1758,8 tr1 ' Ati-25'P.M . the needle . _^ . ; ; ^n -o tr1 ' the needle com. 1 30 _^ 49 30 -30 -o menced movin com+ I 40 SO 15 -3 ' rapidly to the 2 OO 50 IO 29\#191 ; 17 48,5 westward , inten2 30 50 OO 29^ sity at that time 35 4820 29 17 46,5 increasing . 3 55 4740 29 1749 500 4430 -29h V S3\#191 ; Yei7 5 40 44 2O 29e i7 52 > 8 Hazy 615 44 oo 29i 17 54*4 700 43 55 -3 ' - . Clearer 7 40 44 oo -30 800 44 'o -3 ' l7 S* > 7 , \#8222 ; . 9 00 44 00 3O\#191 ; W ShS Easterly , Clear\#8222 ; . and 11 00 4340 -31 l7 54 > 2 LiSht Fme - , A , MIA 4300 -31 1754 . ; .Max . - , easterly A , Mar. J 3d 1 10 A.M. 42 3 < > -31 17 57 > o Easterly Clear and turato\#187 ; . J 26 40 20 -31 17 59\#187 ; 6 Llssht Fine 30 39 5 ' 31 l8 I\#187 ; 3 3 50 38 30 -31 l8 8 > 5 o tl\#8222 ; 510 4040 31 175M Squally o tl Hazy\#8222 ; 5 40 41 2o 31 North end of Needle to the W. S. W. In this position , both magnets were placed to the south of the compass ; the north pole of one magnet , and the south pole of the other , were directed towards the needle , so as to attract each extremity ; the distance from the centre of the box , to the end of the magnet attracting the north end of the needle , was 18,65 inches , and to that attracting the south end of the needle , 28,4 inches ; the needle then made 1 vibration in 8,6 seconds , so that , the directive force was reduced in the ratio of 0,42 to 1 . Direction of Mean A.M. Reading of pTJmp\#161 ; north end of Time that a hovation , Instr . variation , 60 vibrations . 1825 . h. m. 0/ 0 ms . Mar. 14th 15 A.M.S68 30W -26 17 58,5 Calm Fine and Max. easterly 20 68 30 -27 17 58,5 clear , star variation . 2 20 68 30 27 light 2 50 68 30 27 3 10 68 30 27 18 1,2 3 55 68 30 -27 18 3,9 5 10 70 50 -27 18 00 5 50 70 10 27 65 69 20 27. . no. . 18 4,2 7 00 69 35 27J. . J. . 18 2,3 7 30 69 20 27I.\#163 ; 8 00 68 20 27J. . jg. . 18 7,8 9 00 68 20 27J. . o. . 18 19 9 40 68 40 27I\#163 ; IO 30 69 OO 27J..\#163 ; h. . l8 10,2 10 45 68 20 25 11 00 68 30 -25 18 9,3 11 40 69 00 25 Easterly Clear and Noon 71 15 25 17 59,5 Light fine 030 P.M. 71 50 23 Easterly Clear and Max. westerly o 35 72 00 -23 Light fine variation . o 40 71 55 -23 o 45 72 00 -23 0 50 72 30 23 1 00 72 30 -23 17 53 > ' 1 10 73 00 -23 1 20 73 30 23 1 30 74 30 22J ^I 35 75 OO _22j g1 45 75 30 " e -* 2 00 75 30 22. . eg Calm Clear and 25 75 40 -22. . ^. . 17 48 nne 27 76 OO 22 M2 15 76 IS -22 o2 20 76 30 22 H2 30 76 50 22J -f2 40 77 OO 22\#191 ; 35 77 o ' " e 17 5* > 7 3 27 76 55 22\#191 ; North end of Needle to the S 85o W. The line of minimum daily variation . The distance of the nearest end of each magnet placed to the South , from the centre of the compassbox , was , of that attracting the North end of the needle 1 8,6 inches , and of the other attracting the South end of the needle 27,15 inches : under this adjustment , the needle made one vibration in 10,2 seconds , so that the directive power now , was to the undiminished force as 0,31 to 1 . nearly . Direction of Mean A.M. Beading of Fabren Temp.^ north end of Time that a hoDate . ^meof or north end of Fabren ' needle during rizontal needle Winds . Weather . Remarks , &c. Ubserp# ]'j % needle . ' westerly daily took to make vation . Iastr . variation . 60 vibrations . 1825 . h. m. o/ o m. s. Mar. 23d 6 30 A. M. S 83 30W -26 ... ... . . 18 2 Max. easterly var . 7 io 83 30 26 18 2,2 took place at 7 30 83 30 26 2h 5m A. M. 7 SS 83 30 -26 18 1,5 + 98 83 20 26 18 10,7 9 30 83 3 ' ~26 10 10 83 30 23 18 10,5 10 30 83 30 -22 11 18 83 30 22 18 9,3 b 11 50 83 30 21.\#163 ; o4 P.M. 8340 -21 18 3 g\#163 ; o 45 83 50 2oi J-o 15 8420 _2oJ 17 52,8\#163 ; $ 25 84 20 -20 17 53,9..^ 4Max.westerlyvar . 2 45 85 00 _i9j gg 35 85 00 _ i9j 17 56,5 a -a 3 25 85 00 19 } 3g3 SS 85 00 l9l l7 58 > 4 *J3 4 45 S5 5 l9i 17 55 > 6 M"5 20 85 OO -21 Q6 00 85 00 -22 17 50,5 6 20 85 00 -23 7 00 85 10 23I 18 1,8 7 35 85 20 -24 7 55 85 2O 24 17 56 > 7 900 8600 24 i8 0,2 9 15 86 20 24 9 40 86 00 24 17 58,5 11 00 86 15 -25 17 59 Midnr 85 50 z6 ' 17 59 Mar. 24th 1 00 A.M. 85 40 26J 18 00,8 130 8440.26I Calm Clear and Max. easterly var 2 00 S$ 00 27. . na. . 18 2,5 fine 2 30 85 00 27 S2 40 84 00 -27.\#163 ; 2 50 83 50 26|. . 'S,. . 18 2,5 Easterly 3 20 83 40 27 'u Light Ditto 3 55 83 40 -27. . JS. . 12 4,1 6 00 Ss 40 27. . o. . 18 5 , $ 6 S7 83 50 -27..\#163 ; - ! . . 17 54,7 Calm Clear and fine North end of Needle to the NO . The magnets were now placed to the north and south of the needle , with their axes slightly inclined to the magnetic meridian ; the north magnet had its north pole towards the compass-box , at the distance of 29,1 inches from its centre , and the south magnet had its south pole towards the compass-box , at the distance of 30,1 inches from its centre : the time in which the needle now performed 1 vibration , was 14,4 seconds ; so that the directive force was reduced in the ratio of 0,15 to 1 . Ma m Direction of TWof Ma A-MReading of J"** : m north end of Time that a hoDateST Buon'\#171 ; tldOf~-AAS Wind , . Weather . Wk . &c. Buon ' Instr . variation . 60 vibrations . 1825 . h. m. o , o ~"~~ ' " " " mg ___ April 8th 5 10 A. M.N45 30 E -23 18 1,3 East Clear and It will be seen that , 5 SS 45 2O -22 Fresh Fine at the time of the 6 30 45 20 -22 18 0,2 gre ? test westerli\#8482 ; r ' 6\#171 ; c c\#171 ; Ic 20 2O -22 ~22 ** 0,2 m mcrease of direct6 '\#171 ; c c\#171 ; 20 2O ~22 ** iv power in the ho7 20 45 20 _2i\#191 ; 18 12,3 rkoiital needle took 7 5 ' 44 Io 2lj| place , which accounts 8 OO 43 50 21 e 18 3.4 for the great expres9 26 42 20 -20 17 58,8 5i0- ? of for the ? 28 9 26 42 I200 20 _2O -20 : ; '\#191 ; . : il 17 L ; I 58,8 **iinito 5i0- ? ? 10 10 41 50 -20 S 10 30 41 30 -.20\#171 ; 5 11 Io 41 'o -19 ... & . . 18 6 11 30 41 00 18\#191 ; -C Noon 36 10 18I. . Jg. . 17 51,8 o 15 P. M. 35 0.0 18\#161 ; o 30 29 00 18|\#163 ; + ; oo , \#161 ; k -Z : : : : : : : IJ-iS ^.Wi , ^ . 2 50 16 30 17 310 1700 -17 17 44 Ditto Clear and 3 47 17 4 ' -17 17 S3 moderate Fine SS 25 30 -17 17 43 > 5 5 30 25 30 -17 5 oo 27 30 -17 17 37 6 20 27 30 -18 6 35 32 00 19 7 10 33 30 -19 i7 4I,5 8 00 37 00 -19 i7 34,7 9 3 ' 40 00 -20 17 44,6 10 00 40 00 20 17 45,4 . 10 35 40 00 -20 II1 ' 4* Io ~2Oi Easterly Hazy itfer . east . var . Midn* 51 30 20\#191 ; Light ... North end of Needle to the S. E. The needle was held in equilibrio at this point by two bar magnets ; one to the North , with its nearest end from the centre of the compass 26,3 inches ; the other to the South , having its nearest end from the centre x > f the compass 26,6 inches ; the axis of each magnet was slightly inclined to the meridian , and the needle under their influence made i vibration in li , J seconds , the directive power being reduced in the ratio 0^0,24 to i nearly k Direction of Mean A.** " R-Adina of TemP* north end of Time that a ho^1Jate % Date rre0f A or '\#191 ; \#191 ; th end of *"*\#171 ; * ^^ " needle , du\#8482 ; g ^ took to no < jdle make Win* . Weather . Remarks , &c. Date 1Jate % ObserPfM^ or l/ r npedle ^^ " westerly dailj took to make ration , ^ PfMnpedle lustr . variation . 60 vibrations* 1825 h. m. '/ o m. 6 . Apr 12 th 650 A. M. S 4400 E +3 1817,4 ES Hazy Mnx ' easterly var . 700 43 30 4 . 3j Fresh took place at 8 00 43 IO +4 18*0,3 oh3mA . M. 9 32 43 00 +5 * & l6 > 5 10 is 42 55 +6 . 18 19,6 10 32 42 30 -f . 6 nd 11 7 42 30 +6..8 ... 18 12,2 11 30 42 10 +7..'S..\#9830 ; %. . ! . East Snow 11 32 42 00 4-7..^ > . . moderate falling 11 I3 41 55 +7 Jg 05 P\#171 ; M. 4155 +7..t. . 18 I2 > \#171 ; 1 10 4200 +6..\#163 ; . . 1810,3.*,.i ... w Mux.westerlj/ var . 27 42 oo +5 l8 8*7 ^_ 38 41 50 +5 18 8,2 Squally Much 33 57 41 50 4 " 5 ... ... 18 & , t drift 5 00 42 Io +5 l1 59 > 7 5 30 42 4 ' '+56 00 42 40 +5.* ... . . 18 i > 7 6 30 42 40 +57 00 4* 4 ' +4 ^ . l7 5^ > 3 8 00 42 40 + 4I. . , ... 17 58 10 2 5 ' 3 ' +4 ... ... 18 7 Eastward Stars 11 10 5030 +4.w 18 6 > * Squally faintly 11 55 50 Jo +4.* ... . 18 11 visible Apr. 1 3th 17 A.M. 50 o +3 ... ... 18 14 Easterly Cloudy 25 49 30 +2 18 M > 5 moderate 36 50 30 +1 l8 l6 > 7 4o 51 30 i l8 l8 > 5 c *o 40 r -\#171 ; . i fc l8 22,8 600 48 30.1 18 21,5 Easterly Fine , Max. easterly var . 6 30 48 00 i Light clear . 7 00 47 00 Zero..t3. . 18 24,8 NO 7 30 46 20 Zero..\#171 ; i. . Squally 7\#191 ; \#191 ; o 30 ..\#163 ; ... . . 1828,5 with drift 9 00 44 00 + oj. . ! S. . 18 25 > 8 9 50 43 50 + 'I J\#381 ; 10 10 41 00 Zero '\#171 ; o\#171 ; l8 23 > i 10 30 36 00 Zero H+ 11 10 35 40 +1 l8 2l > 2 11 30 36 5 -I1 18 11,8 1c P.M. 37 00 +1 18 8,4 Northerly Hazy 130 3700 +1 ... .** 1758,6 Fresh / Max.wcsttrlyvar . March 22nd . North end of Needle to the S. 83o W. The following summary of the observations at this point , is given here , merely to prevent breaking the preceding series : they were commenced at 6 o'clock in the morning , at which time the north end of the needle was at S. 83o 30 ' W. where it remained until\#163 ; past 9b ; it then moved to S. 85o W. and became nearly stationary until about nh 3om , at which time it was at S. 8 1 ' so7 W. and soon after , I observed it vibrating rapidly in very small arcs , which were continued with different degrees of intensity for the space of a quarter of an hour . During this time , simultaneous observations on the times of vibration of a horizontal needle were made , and as great fluctuations were observed in the intervals of 10 vibrations , I have inserted them in detail , as follows , in order to show the variations of horizontal intensity which take place in short intervals , and to which must be attributed the irregular vibratory motion observed in this needle . Mean Time of Interrala of Observation . 10 vibrat . Remarks . h. m. s , 41 10 3 4,8 Jt appears by these observations\#187 ; that 44 13 33 the intervals of 10 vibrations\#187 ; exhibit 47 ! ^5 3 3 > 5 changes of horizontal intensity to the 50 19 3 2,5 amount of -^th part of those intervals , 53 20,7 3 1,7 in the space of quarter of an hour . 56 Z2,5 3 1,8 In the foregoing observations , when the north end of the needle was directed towards the east or west points of the compass , it will be seen , that the various deflections of the needle rendered it difficult to discover which way its north end had proceeded during the time of westerly daily variation . This anomalous action of the needle exhibited itself so strongly on the 23d of February , that I was induced to compare the nature of some of its deflections , with simultaneous observations , on the times of vibration of a freely suspended horizontal needle ; and as I found , in every instance of comparison , a decided relation between the changes of horizontal intensity , and these deflections , I began to watch the action of this needle more closely , at the times that fluctuations in the directive force of the horizontal needle , had hitherto been observed to take place ; and from its indications , I frequently stated to the Gentlemen making the observations on horizontal intensity , what I considered would be the nature of the intervals they were about to obtain ; which proving correct , no longer left any doubt on my mind , of the cause of these * apparent irregularities . In order , however , to point out more satisfactorily the relation between the changes of horizontal intensity , and the various deflections of this needle , at other positions of its north end , I have annexed the observations on the times of performing 60 vibrations by a horizontal needle , taken during the same time ; but this will not explain all the anomalies alluded to , without also stating , that the fluctuations which frequently took place in the intervals of 10 vibrations , were sometimes observed to compensate one another , so as , in the mean of sixty , to leave no indications of such changes having taken place ; and it is only on these occasions , that the expression for the magnetic in* tensity of the horizontal needle is at variance with the irregular motion of the neutralized needle . On looking over the observations it will also be seen , that when the north end of the needle was directed to the souths ward , between N. 85o E. and S. 85o W. its motion during the time of ^westerly daily variation was generally towards the left hmd9 but when directed to the northward , between N* 85o E. and S\#187 ; 85o W. its motion was then most commonly to the right hand ( see the figure in Plate IV . ) ; and that when held between N. 85o E , and north , a greater daily change obtained than & t any of the other positions , amounting in one instance to 50 degrees ; byt when directed to S. 85P W. no daily variation , or at least a minimum , exhibited itself . With respect to the effect produced on the needle when held between N. 85o E , and north , it appears , from observations on the times of vibrations of a horizontal needle , that an increased intensity generally took place about noon , at which time also , the maximum westerly daily variation generally happened ; and as we have already seen , that the motion of the north end of the needle in this position , during the time of westerly daily variation , was to the right hand , or towards the magnetic meridian , the effect of an increased intensity would be to draw it still further in that direction* and therefore , produce the extraordinary amount noticed , But with the north end of the needle , held between S. 85 ' W. and north , where its motion is still to the righi hand at the time of westerly daily variation , the effect of increased intensity then , would be to draw the north end of the needle to the left hand ) or towards the magnetic meridian ; from whence it is inferred , that these contrary effects balance each other at\#352 ; . 85o W. and produce what has hitherto been termed the line of minimum daily variation . Nevertheless it is a singular coincidence , that the true bearing of this line at Port Bowen ( viz. S > 38o 4 E > ) agrees nearly with Mr. Barlow 's deteiv mination at Woolwich . It would , however* be desirable to have other observations* at plaees differing much in magnetic position\#187 ; before drawing any conclusions as to the probability of its dependence on $ome general cause ; especially , since the needle after remaining absolutely stationary for three\#191 ; ueeessive dap at S.\#171 ; s ' W , commenced moving with its north end towards the left hand , o\#345 ; west point of the compass\#187 ; at half-past three P. M. on the\#191 ; 7th of March ; without any apparent cause whatever , and that it did not again become stationary during the rest of the observations at this point , which were continued until the 5th of April ; in the course of which , as will be seen , its north end sometimes proceeded towards the kft , and at others towards the right handy during the tioie of westerly daily variation . Whether this movement of the needle , on the 27th of March , took place in consequence of the changes of intensity in the opposing magnets ( which were Covered With snow ) > arising from the effects of temperature , or from the cudden variations of intensity of the horizontal needle which take plate in short intervals of time , to which jI am most disposed to attribute it , Is difficult to decide ; it was not considered to be due to the effects of electricity , as there was no appearance of the Aurora the existence of that phenomenon , in the atmosphere , detected by the electrometer . Towards the end of May , however , I commenced another set of observations ( at S. 85o W. ) , but the needle never became stationary throughout their continuance ; its north end sometimes proceeding towards the north , at others towards the south , during the time of westerly daily variation , and that occasionally the needle was observed to vibrate in small arcs ; as already noticed at its other azimuthal positions . It will also be seen , on looking over the preceding observations , that the times of maximum westerly , and easterly daily variation , by this needle , differ on many occasions very considerably from those by the suspended needle v this difference it may be observed , arises from the circumstance of the observations on each needle not being made simultaneously , as well as from the minuteness of some of the phenomena escaping observation by the suspended needle ; but which were elicited by this needle , proportionally to its reduced directive force . Besides these observations on the daily changes of the horizontal needle , I also attempted a similar set on the dipping needle , but the difficulty of adjusting the magnets was such , as to prevent me from obtaining any satisfactory results . Port Bowen , July ist , 1825 . from about N. E. to N.W. at an elevation of from 10 to 20 degrees , with streamers sometimes shooting towards the zenith . At times when it was brightest , although not very brilliant during any part of the winter , I have frequently watched this needle , without ever being able to detect a change , that could be ascribed to its influence .

41141783

2610523

A comparison of the diurnal changes of intensity in the dipping and horizontal needles, at Port Bowen

177

187

Philosophical Transactions of the Royal Society of London

Henry Foster

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6.0.4

transactions

http://corpora.clarin-d.uni-saarland.de/surprisal/6.0.3/?id=41141783

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Meteorology

Astronomy

Meteorology

VII . A comparison of the diurnal changes oj intensity in the dipping and horizontal needles , at Port Bowen . By Lieutenant Henry Foster , R.N. F.R.S. Communicated February 25 , 1826 . A he following comparative observations on the intensity of the dipping and horizontal needles , were made with a particular object in view , which will be proper to explain before giving the details . It was found by observation , that the intensity of the horizontal needle was hourly varying : this appeared by the results already given to this Society in a former paper : but it was doubtful , whether this variation of horizontal intensity of a needle , proceeded from an actual variation in the intensity of the terrestrial magnetism , or from a variation in the amount of its direction , as indicated by the dip itself . The power of the horizontal needle varying as the cosine of the dip , a change to the amount of a few minutes in the dip , at places where it is very great , would be sufficient to explain all the variations of intensity observed in the horizontal needle , without supposing any change to have taken place in the intensity of the terrestrial magnetic force . The variation in dip , however , if it did occur , was too small to be detected by direct observation ; and I failed also , to render it sensible by the application of magnets , as stated in a former communication . My object therefore in making the experiments contained in the following Table , was to ascertain , by several series of vibrations made with the same needle , mounted alternately as a dipping needle , and as a horizontal one , whether or no a corresponding variation of intensity would manifest itself in these two positions respectively ; as ought to be the case , if the diurnal changes of intensity in the horizontal needle proceeded from a general change of intensity in the terrestrial magnetic power . But on the other hand , if the force indicated by the dipping needle should be found to remain constant , then it would be equally clear , that the variations of intensity in the horizontal needle proceeded from an actual change of clip only . As this question is of considerable importance in the theory of terrestrial magnetism , I regret that I had not an opportunity of making a more extended series of experiments of this kind ; but , as far as they go , they certainly appear to indicate , that the alterations of intensity in the horizontal needle , are due rather to a daily change in the amount of the dip , than to any variation in the general intensity of the earth 's magnetic force ; although some change in this also is observable by the vibrations of the dipping needle This explanation of the cause of the change of horizontal intensity , it may be remarked , is consistent with the observations made in Europe , which likewise show an alteration of intensity in the horizontal needle during the day , but in a much less degree than at Port Bowen . Now , if the variation in question really proceed from a change of dip , to the amount of 3 , 4 , or 5 minutes of a degree , the change of intensity in the horizontal needle will be less and less obvious , as the dip decreases ; but if it proceed from a change in the actual intensity of the earth 's magnetism , it ought to be constant in all parts of the world , which is contrary to observation . In making these experiments , a dipping apparatus by DoLLOND , belonging to the Board of Longitude , was used . This instrument had a needle 1 1\#163 ; inches in length , of an oblong shape , and rounded at its extremities ; it was placed in the magnetic meridian , on a pedestal built of stones , and thus afforded the means for ascertaining the variations of intensity in the earth 's magnetism , as indicated by the vibrations of the dipping needle . But as I had not a suitable apparatus for ascertaining the variations in horizontal intensity with the same needle ; a cubical box 12 inches high was prepared , for which I was indebted to the kindness of Captain Hoppner . This box had glass ends , to admit of the vibrations of the needle being observed , and contained at the bottom a horizontal circle , divided to every 5 degrees , for the purpose of measuring the arc of vibration ; it was likewise fitted with a contrivance , by which the needle could be made to vibrate in any arc at pleasure , and the top was so constructed as to allow the suspension of the needle , to be placed directly over the centre of the circle . The suspension consisted of a few fibres of floss silk , attached to one of the extremities of the axis of the needle , just sufficient to sustain its weight , and several inches in length , to lessen the effects of torsion . This box was also mounted on a pedestal , similar to the one on which the dipping apparatus stood , and both were protected from the weather by being placed in a house built of snow . For observing the horizontal vibrations of this needle , a small telescope , having a vertical wire fixed in the focus of the eye-piece , was placed on a stand firmly frozen to the ground , at the distance of about eight feet from the middle of the box , in the direction of the magnetic meridian : when the needle was at rest in its natural direction , a fine thread of light reflected from its end , was bisected by the vertical wire in the telescope ; the telescope having a lateral sliding motion for the purpose of accomplishing this adjustment . In making a set of these observations , the following mode was pursued : the needle being suspended horizontally , the adjustment of the telescope above described was first completed , after which , the needle was made to vibrate at the commencement , in an arc of 60 degrees , by the contrivance already alluded to ; the time at which the reflected thread of light passed the wire in the telescope , was noted by means of a chronometer , and also at every tenth vibration following , until one hundred were completed : the needle was then removed from the box , and placed on its axis in the dipping apparatus ; the time of its performing one hundred vibrations ( commencing as before in an arc of 60 degrees ) was in like manner noted ; the passage of the central point in this case being determined by means of a lens , fixed over that part of the vertical circle to which the needle pointed , When freely supported on its axis and at rest . In this way all the results in the following Table have been obtained ; it may not , however , be unimportant to state , that although the needle , in each of its different positions , always vibrated in the same arc at the commencement , viz. 60 degrees ; yet the terminal arc , in either position/ generally varied . The Table is divided into two parts ; the first contains the observations on the times of vibration of the* needle in its horizontal position ; and the second , those on it when used as a dipping needle . In the first column of each part , is inserted the day of the month ; in the second , the hour and minute at which the observations were commenced ; the third column of each part , contains the mean time in seconds taken by the needle in its different positions , to perform one hundred vibra\#171 ; tions ; and in the fourth , is inserted the temperature of the needle at the time of observation . ist Part , sdPart , Horizontal Needle . Dipping Needle.\#171 ; v en Mean time in Mean time in Date\#171 ; v m^c^ ' menceraent . en Sf'n^ > OIper ' TemPFan* . Date . TuneofComseconds , of perTemp . menceraent . forming 100 Fan* . mencement . forming 100 perTemp . Fah\#171 ; . |n _ vibrations . ' vibrations . 1825 . h. m. s. o 1825 . h. m. 8 . o Feb. 1 2th A.M. 635 2128,6 -17 Feb.i2thA . M. 11 58 405^ 17\#191 ; 1054 2127,6 -17 P.M. o 30 405,7 i7l P.M. 132 2079,9 -17 13th P.M. 3 41 410,0 ~i7i 13th P.M. 142 2103,1 17 14th A.M. 1034 408,0 ---19 } . A..M254 2152,5 '7e P.M. o 12 406,5 -20 14th . A. M.i i 21 2088,2 -20 8 33 408,4 -22 P.M. i 14 2067,7 -20 1000 409,0 21J 9 00 2086,0 -22 11 ia 408,7 -21 A 15th A.M. 041 2107,0 22 15th A. M. 134 ^n^i 22 1048 2115,5 2I IO 32 410,0 -.21 P.M. 844 2064,2 -23 11 35 4o9,6 -21 1029 2071,0 -23 P.M. 89 409,2 -23 l6t\#163 ; A.M. n4 2077,4 -27 943 4o8 > 7 _23 17th A.M. 10 18 2071,0 -22 11 r5 409,2 -22 11 12 2058,2 -21 16th A..M . 10 38 409,9 -28 P. M\#171 ; o 29 2079,5 20 11 46 409,1 -27 19th A^M . 10 l8 2092,2 22J 17th A. M\#187 ; 9 , 42 409,0 -22 u 54 408,5 20 P.M. 1 10 409,0 20\#191 ; i9thA . M.iooo 408,5 23 10 58 408,1 -22 * Mean ... . 2092,33 20J . Mean ... . 408,65 zi ' * The dip of the needle resulting from these elements is 87o 48^8 N. The above results show , that the mean of all the observed times which the horizontal needle required to make one hundred vibrations was 2092,33 seconds , but that differences appear in these times amounting to 94,3 seconds , or ~j part of the interval ; whereas in the dipping needle , in which the mean of the times required to perform one hundred vibrations was 408,65 seconds , the greatest difference is only 5,7 seconds , or -1 part of the interval , which is a much less proportional change than the former . As an additional confirmation , however , that the intensity of the earth 's magnetism is not subject to much variation , I have given in the following Table the results of observations I made on it at the same place in November , 1824 , January and June , 1825 . These exhibit the times in which the needle completed one hundred vibrations in the magnetic meridian , deduced from the mean of the times of its performing four hundred vibrations , with the face of the instrument on each side of the vertical , and the needle reversed on its axis in the two positions . -m'aai~ Ti\#8482 ; *\#187 ; of Mean time in seconds\#187 ; * . -m'aai~ Obtrotion ! Ti\#8482 ; *\#187 ; of of performing 100 Temperature . vibrations . J ? an ' h. ro . s. o November 8th A.M. 10 20 4'4 > 94 ! 3e January 10th A.M. n 45 404,69 22 June 27th A. M. 9 30 406,50 + 47 These results also show , taking into consideration the different temperatures under which they have been obtained , that little or no change in the intensity took place , notwithstanding the observations were made at different hours of the day , as well as at different parts of the year . Therefore , as has been stated , the clange of intensity in the horizontal needle is due , principally , to a daily variation in the amount of the dip ; not tp a real change of intensity in the terrestrial magnetic force . This at least appears to be a legitimate deduction from the preceding observations ; from which circumstance , and that of the daily variation in the direction of the horizontal needle , we are naturally led to the conception of a small variatipn in position of the magnetic axis , corresponding to a revolution of the pplar point round its mean position as a centre , prpduced by the action of the sun , on the magnetism of the parts of the earth , successively exposed to its influence . And , moreover , it seems by no means improbable , that the annual variation of the positipn of the magnetic pole may ultimately be traced to thp s^pye universal cause . I have not attempted to enter into any minute calcul^tipns on this subject , but I believe it will be found , that if the r^cjius of the circle , described by the pole of the general magnetic axis of the earth during the day , be supposed tp subtend at the centre an angle of 2 or % ' minutes , it will reconcile , to a considerable degree of precision , nearly all the observations on the daily variation of the direction , and daily change pf intensity of the horizontal needle , made both in Eurppe arid within the Arctic Circle . If , also , we suppose the magnetic north pole , during the passage of the sun over its merijdi^p , when lying between the pole of the world and the sun , to advance more to the westward , or in a direction contrary to the rotation of the earth on its axis , than it returns tp the eastward , or in the direction of rotation of the earth during the sun 's passage over the opposite meridian , , when the pplp of the world lies between the magnetic pole and the sun , then it follows , that in some certain number of years the magnetic north pole will perform a revolution from east to west round the pole of the earth , and produce an annual change in the variation of the compass in that direction , which is known to obtain . ' That this may be the case , is rendered probable , by considering that the sun at present approaches nearer to the magnetic north pole in its southern , than in its northern passage over the meridian , by twice the north polar distance of the magnetic pole ; and although the reverse takes place on the south pole , yet , as the sun is longer on the northern than on the southern side of the equator , there will be a preponderance of action to carry the north pole forward to the westward , and consequently the south pole to the eastward , as is supposed to be the case by many eminent philosophers in this country . However , these observations will , of course , require to be repeated in other parts of the world , before this hypothesis can be considered as fully confirmed by experiment . In this concluding communication relative to our recent northern magnetic experiments , I beg leave again to express my obligations to Mr. Barlow and to Mr. Christie . To Mr. Christie , for his kindness in permitting the observations on the dip and magnetic intensity to be made in his garden at Woolwich , and for the valuable assistance he rendered me in the equipment of the magnetical instruments supplied to the Expedition , To Mr. Barlow , I stand indebted in a manner which I find it difficult to describe ; indeed it is no more than due to the scientific liberality of this Gentleman to state , that on many occasions , when I have shown him my experiments on the different magnetical subjects wherein I have been engaged , he has kindly given such a direction to my thoughts , as materially to assist me in arriving at the conclusions I have drawn . P.S.That the magnetic pole moves in an orbit round the pole of the earth , was first conceived , I believe , by Mr , Derham , as appears from the Appendix to Philosophical Essays , in three parts , by R. Lovett , lay clerk of the cathedral church at Worcester , published in 1766 , which was put into my hands by a friend , on mentioning to him the theoretical views advanced in this paper . This Appendix contains a brief theory of the north magnetic pole adopted by him from q. passage in Derham 's Physico-Theology , which I shall tran\#187 ; scribe in Mr , Derham 's own words , who , after stating the various discoveries of Norman , Gellibrand , and others , proceeds to say ; " To these discoveries , I hope the reader " will excuse me if I add one of my own , which I deducecji " some years ago , from some magnetical experiments an$ " observations I made ; which discovery I also acquainted " our Royal Society with some time since , viz. that as thp " common horizontal ncedle is continually varying towards " the east and west , so is the dipping needle varying up and " down , towards or from wards the zenith , with the magne* " tick tendency describing indeed a circle round the pole of " the world , as I conceive , or some other point ; so that if " we could procure a needle so nicely matfe , as to point ex " actly according toits magnetic direction* it would in gptfte t\#8364 ; certain number of years describe a circle of about i$gf . " radius round the magnetic poles northerly and southerly.\#8364 ; \#8364 ; This I have for several years suspected , and have had some H reason for it too ; and three or four years ago , mentioning " it at a meeting of our Royal Society , they were pleased to " cause it to be entered in the Journals ; but I have not yet " been so happy to procure a tolerable good dipping needle , " or other proper one to my mind , to bring the thing to " sufficient test of experience ; as in a short time I hope < c to do , having lately hit upon a contrivance that may do " the thing/ ' Mr. Lovett next proceeds to illustrate Mr. Derham 's theory by appropriate diagrams , and then to compute the latitude of the magnetic pole from the best recorded observations at the time on the variation of the compass at two well known places . Having thus obtained 13o 51 ' for the north polar distance of the magnetic pole , or radius of the orbit which it describes round the pole of the earth , he then fixes the year of no variation of the magnetic needle in London to be 1660 , from the observations of Dr. Halley in 1672 ; and from a similar observation by Dr. Bradley in 1750 , he deduces the longitude of the pole for that time , and by this interval of 90 years , he infers the progressive rate of the pole westerly to be in longitude 70 i 12 " every ten years . With these data he has computed a table of variations of the compass for every ten years between 1660 and 1910 , in which he has predicted , with near approximation to what has since been observed , considering the distance of time and want of correct knowledge of its quantity , not only the amount of the variation , but the year in which the magnetic pole arrives at its maximum westerly position . He also states , that in 191 a\#163 ; the magnetic pole will again be on the meridian of London , and that it requires 505 years , 215 days , 8 hours , and 24 minutes , to make a complete revolution round the pole of the world .

41141784

2610523

Account of the repetition of Mr. Christie's experiments on the magnetic properties imparted to an iron plate by rotation, at Port Bowen, in May and June, 1825, together with Mr. Christie's remarks thereon

188

205

Philosophical Transactions of the Royal Society of London

S. H. CHRISTIE|Henry Foster

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http://corpora.clarin-d.uni-saarland.de/surprisal/6.0.3/?id=41141784

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Measurement

Meteorology

Measurement

VIII . Account of the repetition of Mr. Christie 's experiments on the magnetic properties imparted to an iron plate by rotation , at Port Bowen , in May and June , 1825 . By Lieutenant Henry Foster , jR . N. F. R. S. ; together with Mr. Christie 's remarks thereon . Jl REvious to our leaving England in 1824 , Mr. Christie stated to me that he had some time ago discovered singular magnetic properties to be imparted to iron by simply making it revolve about an axis , and that these properties were exhibited in the different deviations which a plate of that metal would cause in a horizontal needle , according as it was made to revolve gently by the hand in one direction or the opposite : wishing me also to pursue these experiments as opportunites offered , in the high magnetic latitudes we were likely to visit in H. M. S. Hecla . The memorandum with which he furnished me on this subject , suggested that the plate should be placed in certain magnetic positions to the compass ; for which purpose , unfortunately , I had no proper instrument . Through the kindness , however , of Captains Parry and Hoppner , I was enabled to employ the carpenter of the Fury in constructing a suitable apparatus ; and I feel much satisfaction in acknowledging my obligations to them , for the ready assistance they afforded me on this , as well as on other occasions . The instrument , which answered the purpose extremely well , is briefly described as follows . Plate V. AB , fig. 1 , is the stand of the instrument , CDE F a wooden frame , across the upper part of which passes a copper bolt , G H , with clamping screws at s s. This bolt was flattened and bent down in the middle , as shown at K , where the compass was placed , LMNO is a copper frame , with two pins , T and V , inserted into it , to carry the circular iron plate , as shown also in the figure . It is obvious , that with this instrument I was enabled to place the iron plate in any latitude by means of the graduated circle aa and plummet/ * , while by turning the frame CDEF in azimuth , it might , in like manner , be placed in any longitude : in all these cases the plane of the plate being a tangent to the sphere . When it was required to place the plate , with its edge pointing to the centre of the meedde , or its plane in the plane of the secondary to the equator and meridian , I then employed the small stand shown in fig. 2 , whioh might be elevated to any height to bring the compass , whioh was placed on its ftop , to the required position . It was also\#9830 ; employed when the plane of the plate coincided with that of the equator . in order to imderstand the [ particular positions in question , it ^will be best to refer to figures 3 , 4 and 5 . Fig.:S , represents the sphere circumscribing the needle viewed on the plane of the meridian ; 4 , on the plane of the secondary ; and 5 , on\#357 ; he plane of the equator . In fig. 3 , C is the centre of the compass , SN the magnetic axis or line of the dip , Ew < Q and e the equator , SEN Q the meridian , SeNw the secondary , n*wse the horizon , ns the horizontal magnetic meridian or axis of\#357 ; he horizontal needle , and^cw the east and tvest line . The fpointsat which Mr. Christie wished observations ito be made , were at E , -S , Q , N , \#191 ; and z < withtke , plane of the plate a tangent to the sphere at each ; that is , at E and Q the plate would revolve about the line E Q , and at S and N about the line S N , &c. But with the plane of the plate in the plane of the secondary , he was most desirous that observations should be made ; and at the points s , w , N and e , fig. 4 . I also made a set of observations at the points e , w , E , Q , fig. 5 , the plane of the plate being in the plane of the equator . In consequence of the extent of the changes in the daily variation , I was under the necessity of making the observations in a different manner from that adopted by Mr. Christie ; they were in general made as follows . The circular iron plate before mentioned , being divided into six equal parts , marked o , 60 , 120 , 180 , 240 , 300 , and the instrument above described so adjusted , that when the plate was placed on the copper pin T or V , its centre would occupy the position required ; the plate was then placed on the pin , with the point o , coinciding with the fixed mark or index , and the direction of the north end of the needle noted ; after which the plate was made to revolve three times for instance , gently by the hand , its upper edge moving from east to west , and o , being again brought to coincide with the index , the direction of the north end of the needle was again noted ; and the same was done , after making the plate revolve in like manner from west to east : the difference between the first and second reading , gave the deviation due to rotation from east to west ; and the difference between the first and third , that due to rotation from west to east The plate was then moved to a distance , in order that an allowance , if necessary , might be made for the change in the direction of the needle caused by the daily variation . After this , the plate Was again fixed in its proper position , with its point 60 coinciding with the index , and the deviation caused by rotation obtained in the same way , and in like manner for the rest of the points 120 , 180 , 240 , 300 , o , in their order , and likewise in the order of succession 300 , 240 , 180 , 120 , 60 , o. The various effects due to the rotation of the plate , when placed in the different magnetic positions above specified , are noted in the tabulated experiments at each : it may nevertheless be proper here to state the nature of these deviations , in the different adjustments of the plate to the compass ; as for instance , in the experiments with its plane in the plane of the secondary , placed at Sand N , fig. 4 , 16,4 inches from the centre of the needle , the deviations were invariably to the east ; when its upper edge was made to revolve from west to east , and to the west in the opposite rotation : at the points e and w effects just the contrary were produced , viz. that while the upper edge of the plate revolved from west to east , the deflections were to the west , and in the opposite rotation to the east ; from which circumstance it was inferred , that there must be an intermediate latitude where no deviations of the needle would be produced by rotation , and this by experiment was ascertained to be latitude 52e\#191 ; North and south , as stated in the observations . The effects of rotation of the plate on the needle when placed with its plane a tangent to the sphere , at the points E and Q , fig. 3 , were considerable , and always to the west , the upper edge revolving from east to west ; but at the other positions NSe and w , no effect due to rotation was observable . The maximum effect of rotation ( amounting to 108o in one instance ) was produced with the plate in lat , 52o y N , long . 270o , thirteen inches from the centre of the needle , and also in lat. 52o fS , long . 90o . These unusual quantities are doubtless attributable to a circumstance I had previously noticed in the voyage of H. M. S. Griper to Spitsbergen , where it was found , that with the ship 's head to the southward , the iron in the vessel neutralized the needle , or nearly so , and thereby left it free to obey any new force impressed upon it ; and so in these cases . In both the positions specified , it will be seen that the needle was nearly neutralized by the plate , and therefore the effect of rotation was more strongly exhibited ; the character of these deflections were generally to the east of zero , or reading previous to rotation : . but when the action of the plate co-operates with that of the earth , the contrary to the above effect of rotation of course takes place . In this case the horizontal intensity rof the needle being increased , the effect produced by rotation is diminished , as will be seen when the plate was placed in lat. 5a'|N , long . 90o , and in lat 52 ' ! S , long . 270o : in both these positions the upper edge being made to revolve from east to west , the needle was deflected to the west . The centre of the plate placed in lat. 52o ~N , long . o ' , and in lat.\#163 ; 2'f S , long . 180o , the upper edge revolving from south to north , the deviations were to the west , and of greater amount than those to the east , caused by the rotation of the plate in the opposite direction . Effects , however , precisely contrary to these last mentioned were produced by the revolutions of the plate , when fixed with its centre in lat. 52o ! S , long . o ' , and in lat. 52'|N , long . 180o . When the plate was adjusted with its plane in that of the equator , and its centre in the various magnetic positions specified in the experiments , very trifling deviations due to rotation were produced , and those probably arose from errors in the adjustments themselves . The following effects were also noticed in the course of these experiments , viz. ( ist . ) In the different adjustments of the plate , it was found in general that the amount of the deviation from zero , due to rotation in the same direction , when the several points on the plate coincided with the fixed mark , was greater or less , according as the plate had been adjusted on the pin in the successive observations , with the several points coinciding with the fixed mark in the order o , 60 , 120 , 180 , 240 , 300 , or in the order of succession 300 , 240 , 180 , 120 , 60 , o ; although the whole amount of deviation due to rotation in opposite directions , was not sensibly affected by this circumstance . This effect is fully pointed out in Table I. and its probable cause suggested . ( 2nd . ) One slow revolution of the plate produced as much deviation as three or more turns ; quick revolutions were always attended with comparative trifling deflections of the needle . The plate retained the magnetic properties imparted to it by rotation , while remaining on the axis , round which it was made to revolve ; * but on its being placed horizontally on the ground , ( which in this place was nearly in the plane of the magnetic equator ) , the effect was destroyed in the course of 10 or 15 minutes ; implying that time is requisite for the complete developement of magnetism in the plate , as well as for the displacement of it , after it has been produced. . This is inferred from the observations of i^ hour only , during which time the direction of the daily variation needle was noted , and compared with that under the influence of the plate . ( 3rd . ) Oscillating the plate in different arcs , with its plane a tangent to the magnetic sphere , after the manner of the balance wheel of a watch , caused considerable deviations of the needleIn this experiment also , quick vibrations produced the least effect . In Table I. the observations are given at length , in order to exhibit the peculiar effect , already noticed , arising from the order of succession in which the points o , 60 , 120 , &c. were in the first instance brought to coincide with the fixed mark . The second column shows this order , and the third column , the zero or reading of the north end of the needle when the plate was placed on the pin previous to rotation . II . Table of the mean deviations due to the rotation of the plate , its plane being in the secondary to the equator and meridian , and its centre at the distance of 16,5 inches from the centre of the needle . ^ '5 Mean of readings of Mean deviation of , g g* S " c 2 north end of needle north end of needle ca Position of the a JJ g after plate had redue to rotation of.jS\#171 ; S -|\#191 ; ^ plate 's centre . g|\#171 ; sj volred , its upper plate , its upper edge.g SS2 *jj Remarki ~a* edge from from\#171 ; .*{ ^ggoo -2 . ____________ 2\#171 ; c_\#163 ; l'I S East to West to East to West to |^ " S J\#163 ; Lat Long. $ -5\#171 ; ~ West East . West East S~ * . ' O/ O ' O/ O/ O ' O ' Oooo 35W io 26 E4 42W11 iE4 jW +15 8 +16J i turn in 1 min. o 180 1 24 E7 39 E5 40W 6 15 E7 4W+13 J9+13I 3 turns , slow . 52$ . So 69 6W68 51W68 57W o 15 Eo 9E+ o 6+12 1 turn in i min. 52J S 180 69 7E 69 12 E 69 12 Eo5Eo5Eo 0+12 1 turn in 1 min. 52I-N o 71 4E 70 59 E 70 47 Eo 5W o 17W+ o 12+18 2 turns in 2 min. 52^Ni8o 71 15W71 6W71 8W 'o 9Eo7E -fo 2+18 1 turn in 1 min. 90 S1 00 Eo 55W 4 37 Ei 55W 3 37 E5 32+17 3 turns , slow . 90 No 22 E3 19W 46E3 41W 3 44 E7 25 +12 i turn in 1 min. It appears from these observations , that in latitude 52o y North or South , the deviation due to rotation nearly vanished ; but I do not profess to have got the latitude of this point to any great degree of accuracy , the nature of the construction of the instrument used , not admitting of the measure ments from the centre of the plate , to that of the needle , being taken sufficiently near for that purpose ; but I think it is obtained within the limits of a degree . Foster , at Port Bowen , in 1825 . Having a considerable time previous to the sailing of the late North-Western Expedition , in 1824 , discovered that peculiar magnetic effects were produced in iron by rotation , I was desirous of having some of the experiments which I had made , repeated under the very interesting circumstances , as connected with magnetic phenomena , in which that expedition was likely to be placed . Mr. Foster readily offered to do this ; and I feel happy in having this opportunity of acknowledging my obligations to him for the zealous and careful manner in which he performed the task which he had so kindly undertaken . The peculiar effects produced on the magnetic needle by the rotation of an iron plate , of which I have given an account in a Paper published in the last volume of the Transactions , are in this latitude ( magnetic ) rather minute ; but I expected that in the high magnetic latitudes likely to be visited by the expedition , these effects being increased in the inverse ratio of the cosine of the dip , they would become very conspicuous ; and that some phenomena which here , from their extreme minuteness , would escape observation , in those latitudes would be easily observable . The result has fully answered the expectations which I formed : at Port Bowen , where the dip is more than 88 ' , the phenomena were exhibited on so striking a scale , and the interest which they excited was such , that Mr. Foster devoted much more time to their investigation than I could have at all contemplated , knowing hov/ fully his time must be otherwise occupied . To those who have previously read my Paper on this subject in the Transactions , the general accordance of the results in the foregoing tables , and those which I obtained , must be quite manifest ; as however they exhibit some differences , I shall here briefly point out the agreement between the original experiments and this repetition of them , and likewise those discordances , and at the same time indicate what I consider to be the cause of some of these apparent discrepances . In all the observations which I made , the deviations of the needle due to the rotation of the plate , depended both in extent and character , not upon the situation of the plate with respect to the axis and equator of the horizontal needle itself , but upon its situation with reference to the axis and equator of an imaginary dipping needle having its centre coinciding with that of the horizontal needle ; and this appears most clearly to have been the case at Port Bo wen . In every instance the direction of the deviation due to rotation was the same at Port Bowen as I had found it here , the relative positions of the plate and needle , and the direction of rotation being the same in the two cases . When the plane of the plate was in the secondary to the equator and meridian , I had found that the mean deviation due to rotation in latitude o was + i ' 36 ' and in latitude 9 ' > o ' 45 ' : at Port Bowen the corresponding deviations were + 14o 14 ' and 6 ' 28 ' , which are as nearly in the same ratio as we could expect , considering the irregularities which take place in the individual observations in the latter case . The situation of the point where the deviation due to rotation vanishes , is somewhat different in the two cases ; Mr. Foster 's observations giving its latitude 52'f and mine 54'^ . The method by which Mr. Foster was under the necessity of determining the situation of the plate 's centre , as referred to that of the needle , did not , as he states , admit of considerable accuracy , but the errors to which it was liable would scarcely account for the difference in the two cases . I cannot attribute this difference to errors in estimating the situation of the plate 's centre in my own observations , since this was determined on the graduated limb of the instrument by the index on the arm jon which the plate was carried , and the effect of any error of centering in the compass would be counteracted by the opposite readings . As , however , the situation of this point is by no means an indifferent question in the theoretical investigation of the phenomena dependant upon rotation , I shall , when I have sufficient leisure , repeat my observations . When the plane of the plate was a tangent to the sphere , and its centre in the meridian , I had found that the deviation due to rotation vanished when the plate 's centre was at the pole , and was a maximum when in the equator : according to Mr. Foster 's observations it likewise vanishes at the pole , but the maximum takes place at a point intermediate to the equator and south pole in longitude 90o , and to the equator and north pole in longitude 270o . The situation of the point of maximum deviation at Port Bowenx I have no doubt arose , as I pointed out to Mr. Foster , from this circumstance , that when the centre of the plate is in south latitude in longitude 90 ' , or in north latitude in longitude 470 ' , the directive intensity of the horizontal needle is diminished bythe attraction of the iron plate ; and although this diminution would produce effects scarcely observable here , where the intensity of the horizontal needle is great , and the deviation due to rotation very small , yet when the case is reversed , as in the Port Bowen observations , the effect will be so sensible , that the increase in deviation from this cause will much more than counterbalance the diminution which arises from the centre of the plate being nearer to the pole . The effects that would be produced under these circumstances will be most evident , by considering how a dipping needle would be affected , and referring its deviations to the horizontal plane , remembering that in all cases an increase of dip caiises an increase in horizontal deviation , and the contrary . When the centre of the plate is in south latitude longitude 90o , and in north latitude longitude 270o , the attraction of the plate tends to increase the dip , and to diminish it when in south latitude longitude 270'* and north latitude longitude 90o ; so that in the former cases the deviation will be increased from this cause , and in the latter diminished . This effect was so great that in one instance the zero , or reading of the north end of the needle previous to rotation , corresponding to the point 240 on the plate , was 97 ' W , 36 ' E , after rotation in one direction , and 144o E , after rotation in the other , giving no less than 108o for the deviation due to rotation in opposite directions : corresponding to the point 180 on the plate , these were 86 ' 40 ' E , 42o 10 ' W , and 20o 10 ' W , giving only 22o for the deviation due to rotation . By referring to Table I. in my Paper , it will be seen that there are indications of the same effect , since in longitude 90o , the deviations in south latitude are greater than the corresponding ones in north latitude , and the reverse takes place in longitude 270o ; but as the differences are very small , I , at the time of making the observations , rather attributed them to errors in the adjustment , than to any other cause . When the centre of the plate was in the secondary to the equator and meridian , and its plane a tangent to the sphere , I had found the deviation due to rotation so small , that it might be considered to vanish : at Port Bowen , however , the absolute deviation was so great , that in some parts of this circle the deviation due to rotation became sensible ; and it would appear that the locus of the points where this deviation vanishes is a line of double curvature , passing from the south pole on each side , a little north of the secondary , down to its intersection with the equator , and then a little south of the secondary to the north pole . The signs which I have prefixed to the deviations in Table IV . of Mr. Foster 's observations , indicate the course of this curve . The whole of the results in Mr. Foster 's observations perfectly agree with the law which I have given in my Paper as embracing all the phenomena dependant upon rotation , and even the differences which I have noticed between my own observations and these , are precisely such as we should expect , according to this law , to be observable in a change of the complement of the dip from 200 to 20 . The results obtained by the repetition of my experiments at Port Bowen , prove that the phenomena depending on rotation are by no means unimportant as connected with the practical problem of correcting the attraction of a ship on the compass by means of an iron plate . Having observed the effects that were produced on the needle by the rotation of an iron plate previous to the sailing of the Leven and Barracouta , in the spring of 1822 , these vessels being furnished with correcting plates , I communicated the discovery to Mr. Barlow , and stated that probably the correction might be sensibly affected by it , unless rotation , in applying the plate , were prevented , by having the pin so formed that the plate could only be slid on . The preceding observations prove clearly the importance of attending to this , especially in high magnetic latitudes , should circumstances require the removal and replacing of the plate , since there can be no doubt , from the magnitude of the deviations arising from rotation , observed by Mr. Foster , that if in replacing the plate , it were made to revolve , although it might be in precisely the same situation as before , its magnetism would be so materially changed , that the attraction of the ship would no longer be corrected by it . Should such a circumstance take place , it may be proper to mention that the plate would be restored nearly to its original state , by allowing it to remain for some time with its plane in that of the magnetic equator . S. H. CHRISTIE . Koyai Military Academy , 10th January , 1826 .

41141785

2610523

Observations to determine the amount of Atmospherical Refraction at Port Bowen in the Years 1824-25

206

230

Philosophical Transactions of the Royal Society of London

W. E. Parry|Henry Foster|J. C. Ross

fla

6.0.4

transactions

http://corpora.clarin-d.uni-saarland.de/surprisal/6.0.3/?id=41141785

http://www.jstor.org/stable/41141785

Astronomy

Meteorology

Astronomy

IX . Observations to determine the amount of Atmospherical Refraction at Port Bowen in the Tears 1824-25 . By Captain W. E. Parry , R. JV ' F. R. S. Lieutenant Henry Foster , R. JV ' F. R. S. and Lieutenant J. C. Ross , R. JST . F. L. S. 1o ascertain correctly by actual observation the amount of atmospherical refraction at low altitudes and at various states of the barometer and thermometer , is a problem which has long occupied the attention of practical astronomers ; and many elaborate theories have also been given to explain the anomalies which have hitherto attended the most careful observations . In Mr. Ivory 's Paper , printed in the Philosophical Transactions for 1823 , he states ( page 495 ) , that his table of refractions has been constructed merely with the view of comparing the theory in the paper with observation . He adds , however , " that it would be more satisfactory to determine " the same quantity ( / ) by the comparison of many observed " refractions at low altitudes between the distances of 85 " and 88 degrees from the zenith ; and by this means a " table might be constructed that would be deserving of " greater confidence/ * With a view , therefore , to supply the desideratum alluded to , three distinct series of observations were made at Port Bowen , by Captain Parry , Lieutenant Foster , and Lieutenant Ross ; the details of which are given in the following Paper . Various methods suggested themselves for the determination of this question . The first was to measure the zenith distance of known stars at a given moment , with the repeating circle , and then to have computed the true altitude ; whence the actual refraction might have been deduced . The difficulties , however , attending the use of the repeating circle , during the winter of the polar regions , have already been alluded to on several occasions , in the accounts of the two preceding voyages of discovery . The most material of these consist in the extreme contraction of the spirit in the long level , when filled in the usual way ; the instantaneous freezing of the breath or other vapour on the glasses , obliging the observer to hold his breath during each observation ; and the pain , amounting to the sensation , and producing the effects of burning consequent on touching intensely cold metal with the naked hand . The first of these was obviated , on the present occasion , by inserting a larger quantity of spirit than usual , so as to keep both ends of the bubble in sight , even during the most intense cold : this latter circumstance , however , afforded the opportunity of remarking an increased sluggishness in the level at very low temperatures , arising possibly from a certain degree of thickening in the spirit , which required the instrument to stand unmoved for at least two minutes after the contact had been made , in order to insure an accurate reading . It is unnecessary to point out , how unfavourable to minute accuracy this circumstance must prove , in observing an object having quick motion , either in altitude or in azimuth . A set of zenith distances , consisting of only eight observations , cannot , indeed , under such circumstances , be satisfactorily obtained in less than thirty-five or forty minutes . If to the difficulties already mentioned be added the annoyance sometimes experienced by the extinction of the lamp for illuminating the wires during an observation , in consequence of the freezing of the oil ; the frequent occurrence of snow drift ; and the haze which usually hangs near the horizon during a Polar winter , it must be admitted , that the repeating circle is not calculated , under such circumstances , either for obtaining numerous observations , or for ensuring the degree of accuracy indispensibly requisite in observations for determining the amount of atmospherical refractions . Another method was suggested by Captain Kater , in April , 1824 , which is explained in the following words : " Select a star which passes the zenith , and when this star " and the Pole star are at the same altitude , take the distance " between them by means of the repeating reflecting circle ; " do the same when the star is in the zenith , and also when " upon the meridian under the Pole . From the first observa " tions the true zenith distance of the stars may be readily " obtained . By observations made when the star is in the " zenith , the absolute refraction of the Pole star will be " given , and from the observations made when the star is " under the Pole , the refraction at that altitude can be easily " deduced . Pursue the same method with other stars , care " fully marking at each observation the time and state of the " barometer and thermometer . We shall thus be furnished with " data , from which the refraction at the various altitudes can " be computed with facility and accuracy . " On considering , however , the difficulties already detailed in the use of the repeating circle , which rendered it impossible to take advantage of this ingenious suggestion of Captain Kater ; it occurred to Lieutenant Foster , that a more simple and accurate method of determining the amount of refraction , would be to observe the setting of stars within certain limits of azimuth , behind the high land which encircles this harbour , and then determining at leisure the zenith distance of that part behind which the star set . As the ruggedness of the land , however , combined with the frequent alteration of the star 's azimuth , would materially affect results thus obtained ; Captain Parry proposed , as a modification of this idea , to place a board edge-wise , and strictly horizontal , on the spot behind which the star set , thus rendering it unimportant upon what part of the board the occultation of the object took place , as well as affording more ready means of obtaining its apparent altitude . Two boards were accordingly fixed with all possible firmness and accuracy upon a neighbouring hill , to the westward of the observatory , for observing the setting of a , Aquilas and Arcturus respectively , the board for the former being on aN 75't W bearing , distant 924 feet , and for the latter N 40o W , 1590 feet . The observations by Captain Parry , given in Tables IL and VI . , were made with a small theodolite , having its legs immovably fixed by freezing , across a cask filled with sand ; those inTable I V.by a ship telescope , two feet in length , securely attached to the cask itself , and having no motion whatever . Lieutenant Foster 's observations contained in Tables VIII . to XL inclusive , were made with a small repeating circle by DoLLOND , furnished with tv/ o telescopes , which afforded the means of obtaining double observations of each star the same evening . This instrument stood 122 feet above the level of the sea , on a cask filled with sand , firmly frozen to the ground , and was secured from the weather by a suitable covering . The observations by Lieutenant Ross , in Tables XIII . to XV . inclusive , were obtained with a small variation transit instrument as an upper telescope , and those in Table\#171 ; XVI . and XVII . by a pocket telescope below ; both being fixed to a cask filled with sand . None of the instruments used by either of the three observers were removed , till after the completion of the whole series of observations . The hour angle by which the true altitude of the setting star was determined , was obtained by taking its right ascension from that of the meridian , at the time of observation , as found by transits of well known stars , which took place within three quarters of an hour of the other star 's setting , thus rendering the observations as independent as possible of any want of uniformity in the rates of the pocket chronometers employed by the observers . The transits were taken exclusively by Lieutenant Foster , and comparisons with the chronometer he employed , were taken by the other observers about the time of transit , in order to deduce their horary angles , contained in the respective Tables . The position of the transit instrument was rigidly verified by the transits of high and low stars in their passages across the meridian , as well as by a constant reference to a meridian mark , and by the most minute attention to the level . The heights of the barometer , and of the thermometer , suspended with its bulb on the same level with the observers in the open air , were taken at the time of every observation . The registered height of the barometer , however , in the Tables , has been corrected for instrumental errors , and brought up to a certain temperature , which is specified at the head of each of the columns containing it . an The latitude , 73o 13 ' 39^,4 N.* used in these computations , is the result of 91 sets of observations on Polaris , at different horary distances from the north and south meridians , by Captain Parry and Lieutenant Foster ; employing Dr. Young 's Table of Atmospherical Refractions , published at the end of the Nautical Almanac for each year . As soon as the sun afforded sufficient light for obtaining the apparent altitudes of the boards from the respective telescopes , observations were commenced for that purpose . The circle used by Lieutenant Foster afforded the direct means of doing this , for the upper telescope , by which the zenith distance of the edge of the board at the spot where the star set , was at once obtained by observation . The angular distance between this telescope and the lower one , as seen from the board , was determined by means of a double wire micrometer , attached to one of Dollond 's achromatic telescopes 46 inches focal length , the object-glass of which was let into the board , so as to make its centre exactly coincide with that part behind which the star set . The telescopes employed by Captain Parry and Lieutenant Ross , not being attached to an instrument calculated for measuring zenith distances , required some further contrivance to obtain the altitudes of the boards with respect to them . In order to place the repeating circle precisely at the same altitude with Captain Parry 's upper telescope , a levelling staff was fixed into the ground , half way between the place of observation and the board . This being adjusted by sliding up or down till a fine brass point on its upper end exactly . The dements of this result , are given in the Appendix to Capt. Parry 's Narrative of the Third Voyage for the Discovery of a North West Passage into the Pacific Ocean . coincided with the edge of the board , When seen through the upper telescope ; the repeating circle was also raised or lowered until the same coincidence obtained , when looking through its telescope . The accuracy of the position thus obtained was finally verified by observing the setting of the star , through each telescope , when it was found to disappear to both observers at the same instant For the altitude of the board , with respect to the lower telescope used by Captain Parr v , a short staff , exactly equal in length to the measured distance between the telescopes , was fixed vertically above the board , and the zenith distance of its well defined top observed by the repeating circle in its formar place . And as a confirmation of the results thus obtained , the method described above , as adopted by Lieutenat Foster , by means of the micrometer , was also resorted to ; a mean of the two methods ( which differed a/ #,8 ) , being used in the computation of the refractions . Lieutenant Ross 's zenith distances were obtained by a repeating circle , placed on the same cask which held the telescopes he employed , the angular distance between each of these , and that of the circle ( when directed to the board ) , being determined by repeated observations with the micrometer , fixed upon the respective boards M the manner already described . In some instances , lieutenant Ross observed the re-appearence of a Aquilae under the boa\#357 ; d , thus obtaining an observation at another altitude . The corresponding zenith distance of that part of the board was determined by measuring with the micrometer , the angle subtended by the board at the place of observation . The zenith distances of the boards , as obtained by the respective observers , are given in the Tables attached to the corresponding observations for refraction , except those of Lieutenant Ross , the details of which , were unfortunately left on board the Fury at the time of her loss . While making the above mentioned observations for the zenith-distances of the boards , Captain Parry had occasion to notice , on the 28th of February , some anomalies which had never before occurred , and which were at first attributed to some slight and imperceptible change in the position of the repeating circle ( see Table III . ) On-continuing the observations , however , it soon appeared that the changes coincided nearly with particular times of the day , the greatest zenith distance always occurring when the thermometer stood the highest , and the weather was most calm . To clear the zenith distances of this effect of refraction , the repeating circle was carried up the hill , the object-glass of its telescope being placed in a notch cut in the board , as already described above in using the micrometer ; when by several days ' observations , continued from morning till night , it was found that the same phenomenon as before occurred , the zenith distance of the station below uniformly increasing from the morning till the afternoon , and again decreasing as the sun fell . Two sets of observations taken at the board after midnight , by means of a lamp viewed through the tube of the telescope , at the lower station , gave nearly a mean of all the other observations . Thus it appeared that whether observed from the top or the bottom of a hill whose altitude was 4'i , an increase of zenith distance ( varying from 9 " to 1 7 " ) , took place about the same hours , indicating a comparatively rare medium near the surface of the ground , and giving such a curvature to the visual ray , as to produce a similar effect at both stations . On looking over each individual 's observations , it will be seen , that great changes in the amount of atmospherical refraction took place , without any correspondent change in the state of either the barometer or thermometer ; and , although the mode of observation adopted by us , is not wholly free from objection , inasmuch , as the ray of light from a bright star may suffer some degree of inflection , by passing over a sharp edge ( such as the boards placed edgewise would present , whereby their apparent altitudes would not be exactly those of the stars at the time of observation ) ; yet we do not consider this circumstance the cause of the anomaly alluded to , for we never entertained the slightest doubt as to the moment of either of the stars ' disappearance , both being always instantaneous : and , moreover , when it is recollected , that the use of instruments , proper for measureing altitudes on these occasions , in such a climate , is attended with the difficulties already described in this Paper , it will , in all probability be admitted , that this mode of observation , is at least , calculated to diminish the errors necessarily arising from the use of instruments , under such circumstances . It is , however , with diffidence that we submit the following tabulated results of the preceding observations , for comparison with the various theories , which have from time to time been advanced by many eminent astronomers and mathematicians , to account for all the irregularities which have been noticed in the most careful observations on this important subject . Recapitulation of the mean results , of the preceding Observations . Stars Apparent Barometer Temperate . Obser ved No. of ^ , Observed . Altitude . Corrected . Fahrenheit . Refraction . Obser. ^ , UDserver . o/ / / Inches . o ' / / r7 38 0,52 29,749 32,6 823,18 17 Lieut. Ross . tew\#8482 ; s ; S. & 33S =S5 533\#187 ; }"-.*\#171 ; t 7 31 38,62 29,791 23,58 8 23,95 34 Capt. Parry . f4 40 38,0 29,785 33*37 lz 48,17 10 Lieut , Ross . 4 39 3M 29,742 -31,1 13 4,73 23 Lieut. Foster . 4 39 1,8 29,748 30*85 12 51,4 15 Lieut. Ross . ^AfluilaJ 4 38 58,03 29,795 -3i*8 13 4,72 24 Capt. Parry . *AH A^ 4 37 41,08 29,689 -33*37 '3 o > 42 IO Lieut. Ross . 4 36 32,08 29,808 29,0 13 9,37 32 Lieut. Foster . 4 36 3,88 29,712 3i > 35 12 58,85 12 Lieut. Ross . L4 32 32,34 29,761 -29,94 13 12,51 27 CaptParry . The original register of the height of the mercury in the barometer , after being corrected for instrumental errors , has been brought up to the temperature of + 50o of Fahrenheit , in the observations by Captain Parry and Lieutenant Ross , but to + 48 o only , in the observations by Lieutenant Foster . Port Bowen , July 10th , 1825 . From the Press of W. NICOL , Clevelandrrotu , St , James 's .

41206195

2610523

The Bakerian Lecture.\#x2014;On the Electro-dynamic Qualities of Metals

649

751

Philosophical Transactions of the Royal Society of London

William Thomson

fla

6.0.4

transactions

http://corpora.clarin-d.uni-saarland.de/surprisal/6.0.3/?id=41206195

http://www.jstor.org/stable/41206195

Electricity

Measurement

Electricity

Some observations of Regnault 's having appeared to indicate 240 ' Cent , as , more nearly than 300 ' , the temperature of the hot junction which gives the current its maximum strength , I concluded the following proposition : 17 . " When a thermo-electric current passes through a piece of iron from one end kept at about 240 ' Cent.* , to the other end kept cold , in a circuit of which the remainder is copper , including a long resistance wire of uniform temperature throughout , or an electro-magnetic engine raising weights , there is heat evolved at the cold junction of the copper and iron , and ( no heat being either absorbed or evolved at the hot junction ) there must be a quantity of heat absorbed on the whole in the rest of the circuit . When there is no engine raising weights , in the circuit , the sum of the quantities evolved , at the cold junction , and generated in the ' resistance wire , ' is equal to the quantity absorbed on the whole in the other parts of the circuit . When there is an engine in the circuit , the sum of the heat evolved at the cold junction and the thermal equivalent of the weights raised , is equal to the quantity of heat absorbed on the whole in all the circuit , except the cold junction^ . " 18 . Hence , if the reversible part of the effect of a current from hot to cold in iron is an evolution of heat , the corresponding effect in copper must be a greater evolution of heat . But if , on the other hand , a cooling effect be produced by a current from hot to cold in iron , there must be either a less effect of the same kind , or a reverse effect , in copper . It is left to experiment to determine which of the two hypotheses is true regarding iron ; and should it turn out to be the latter , to ascertain which of the two remaining alternatives regarding copper must be concluded . With this object I commenced the experimental researches which I now proceed to describe . SS 19 to 77* Experimental Investigation of the Electric Convection of Heat in Copper , in Iron , and in some other Metals . SS19 , 20 . Unsuccessful attempts , andjirst result . 19 . I began , more than four years ago , by observing carefully the ignition produced in short wires of copper , iron , and platinum by electric currents alternately in the two directions , thinking that some of the effects described by various experimenters , as showing a superior heating power in the positive electrode , might possibly be dependent on the convective agency which I was endeavouring to discover . But I never observed the slightest variation in the position of the incandescent part of the being then guarded against irregular contacts by a little square of pasteboard pressed between the iron squares , a half-square of pasteboard between the first-mentioned iron square and the portion FCH of the connecting copper ( see fig. 49 ) , and fragments of paper and pasteboard elsewhere , the whole was placed , with the secondmentioned square lowest , in a copper cradle lined with paper , and resting between the horizontal edges of the flat poles of the Ruhmkorff electro-magnet used in the preceding experiment . 170 . The positions of the magnetic poles of the squares , of the bent connecting piece of copper , of the testing conductor , and of the galvanometer electrodes are indicated in fig. 55 , but , to avoid confusion , the principal electrodes are not shown . Fig. 55 . A current from the four large double cells , connected so as to constitute in all a single element of Daniell 's , exposing 10 square feet of zinc surface to 17^ square feet of copper , was then introduced by the principal electrode soldered to the edge MD of the upper square , and drawn off by the other principal electrode , namely , that soldered to the edge of the lower square lying exactly below the edge MH of the upper . The course of the current into the principal channel between these electrodes would be across the upper square from MD to HC , and across the lower square from the edge below CD to that below HM ; also , in the secondary channel between the same electrodes , from T soldered to the first through the testing conductor , to its other end U soldered to the second . 171 . A fixed galvanometer electrode being ( S 168 ) soldered to the middle point , N , of the connecting-copper , the other electrode of the galvanometer was moved along the testing conductor till a point , O , was found at which it might be applied without giving any deflection . By moving it -g^th of an inch on either side of O very sensible deflections were obtained , and therefore a yard of copper wire was soldered by its ends to points S and Qa quarter of an inch on each side of O , and was used instead of the " scale " of the testing conductor described as used in the first three experiments . The neutral point , O ' , on this multiplying branch having been found , the galvanometer circuit was broken , and the electro-magnet was excited by six of the small iron cells . On closing the galvanometer circuit again immediately , a considerable deflection was observed , to correct which the moveable electrode had to be moved through about two or three inches from O ' towards Q. On unmaking the electro-magnet a reverse deflection in the galvanometer was observed , and was corrected by bringing back the electrode to Of . The same result was obtained when the magnet was made in the reverse way , and never failed to appear , to an unmistakeable extent and with perfect consistency , after the operation had been repeated many times and varied in every possible way\#187 ; 172 . It showed that the effect of the magnetization was to increase the resistance relatively in the upper square of iron , and to diminish it relatively in the lower square . I concluded with confidence that the electric conductivity of magnetized iron is greater across than along the lines of magnetization . 173 . Exp. 6 . A double experiment , to test the absolute nature of the two effects of which the difference was shown in the preceding experiment . A divided current from the battery was made to pass through the two squares by electrodes , of which one was soldered to the middle of the copper band connecting them , and the other clamped to the now united extremities of the bundles of copper wire which had served before to lead in and out the whole current in the preceding experiment . As testing conductor was used the same piece of copper wire which had served as the fixed galvanometer electrode in the preceding experiment , with its end which had been connected with the galvanometer now soldered to the junction of the two copper branches of the divided channel ( the resistance of each of which was found to be nearly equal to that of the iron square with which it is connected ) . The testing wire used in the preceding experiment was cut in two , one part to serve as fixed galvanometer electrode in one , and the other in the other of the two experiments which it was intended next to make . I first attempted to test the effect on the conductivity of the upper of the two squares produced by the magnetization which in it is along the lines of current . I found , however , on fixing the copper wire proceeding from one side of that square to one electrode of the galvanometer , and applying the other to the testing conductor in the usual way , that the circumstances were constantly varying , and that the point to be touched to give no deflection shifted rapidly along the testing conductor . Hence I gave up this part of the experiment , of which the result might be anticipated with certainty from the experiment on the effect of magnetization along the line of current described above ( Exp. 1 . S 155 ) , and I gave the whole time during which the experiment could be continued , to an examination of the influence of the electro-magnet on the current in the branch leading through the lower square across its lines of magnetization . Accordingly , the galvanometer electrode , which had been united to the part of the old testing conductor terminating in an edge of the upper square , was transferred to the other part of the old testing conductor , that is , to the part terminating in a side of the lower iron square . The same new testing conductor was still used ; and as soon as a point could be found on it which gave no current when touched by the moveable galvanometer electrode , points about\#163 ; of an inch on each side of it were taken , and a multiplying branch of one yard No. 18 copper wire was soldered by its ends to them . Before , however , the effect of the magnetism could be decidedly tested , the zero-point had moved off the multiplying branch , which had accordingly to be shifted along the testing conductor to get into range again . The same process had to be gone through a great many times , and at last , after the current had been flowing continuously through the two squares and the divided copper channel for about five hours , the zero-point became sufficiently steady to remain on the multiplying branch when fixed at the right place on the testing conductor , and to allow a decisive experiment to be made . The result was a very slight effect , proving a diminution of insistence in the iron square . 174 . The cause of the longcontinued variation in the conditions of electric equilibrium between the testing conductor and the fixed point on the edge of the lower square , was clearly the gradual warming of the long copper wires extending up from this point , due to the conduction of heat generated in the iron squares by the electric current ; and it would obviously be much diminished by using a simple form of conductov with only one iron square at a time , and with the reference conductor kept near it , so as to acquire quickly whatever temperature it would rest with during the flow of the current . I accordingly made the following experiment , choosing first the effect of transverse magnetization , as the experiment just described had not been of a satisfactory kind , although apparently conclusive , while the first experiment of the series ( Exp. 1 . S 155 ) had been less unsatisfactory in point of steadiness , and had led decisively to a conclusion regarding the effect of longitudinal magnetization on the resistance of a conductor . 175 . Exp. 7 . A square of sheet iron like those used in the last experiment ( four square inches , weighing 103 grains , and consequently about ^th of an inch thick , ) was soldered along one edge to a slip of lead of the same width , about twice as thick and about one-half longer . To the opposite edge of the iron square was soldered a stout copper slip an inch broad and equal in length to the side . l'e piece of lead was bent round , so as to give a straight part lying about\#163 ; of an inch from the plane of the iron , and to extend about as far as the copper slip soldered to the other edge of the square . A current from an arrangement of the cells ( SS 63 and 64 ) constituting a powerful single element of Daniell 's was sent through the iron square and the lead band , by electrodes clamped to one end of the lead and to the copper slip fixed to the other edge of the iron . A point in the lead slip having been found , such that the galvanic resistance between it and the edge next the iron was nearly equal to the resistance in the iron square itself , a testing conductor ( two yards of No. 18 copper ) was soldered by one end to that point in the lead , and by its other end to the middle of the edge of the iron Fig. 56 . -1 jCupper iron Lead square to which the copper slip is attached . A copper wire , to serve as fixed galvanometer electrode , was soldered to the lead band , at a point in the middle of its breadth close to its edge of attachment to the iron . A copper cradle was put between the flat poles of the electro-magnet , as before ( see above , S 161 ) , and covered with a piece of paper . The iron square was supported upon it in a position with the line joining the poles perpendicular to the line of the current through it . Then , the current being kept steadily flowing through the iron and lead band , a zero-point was found on the testing conductor , and a multiplying branch ( one yard of No. 18 copper ) was soldered with its ends ' of an inch on each side of this point , in the usual way . The zero-point on this multiplying branch was almost immediately found , and continued on the whole very steady from the first . The galvanometer circuit being broken , a magnetizing current from six small iron cells was sent through the coils of the electro-magnet , and the needle of the galvanometer was let settle ( as it could be in a few seconds by the aid of a little magnet held in the hand ) into its position of equilibrium as affected by the direct force of the magnet . On completing the galvanometer circuit again , with its moveable electrode on the same point of the multiplying branch as before , a current was made sensible by an excessively slight deflection . The galvanometer circuit being broken , and the electro-magnet reversed , a similar deflection was found in the galvanometer on again completing its circuit . It ceased , as nearly as could be discovered , when the electro-magnet was unmade , and was uniformly observed when the magnet was made again either way , in a great many repetitions . The current indicated by the galvanometer when the magnet was made was always such as to be corrected by carrying the moveable electrode from its previous zero-point , along the multiplying branch , towards the part of the testing conductor terminating at the iron square , and therefore indicated an increase of conductivity in the iron . The effect was so very slight , that I could scarcely determine how much the moveable conductor had to be shifted to correct it . I intend to repeat the experiment with similar arrangements , but with two or three times as powerful a current through the electro-magnet , which ought to give about four or nine times the amount of effect . In the mean time , however , I am quite convinced that I have observed the true result , and I conclude that the electric conductivity of iron is increased by magnetic force across the lines of current . 176 . Exp. 8 . To show the variation of a line of electric equilibrium in a circular disc of iron conducting electricity between two opposite points of its circumference , when subjected to magnetic force in a direction at an angle of 45 ' to the line joining these points . A circle 2*3 inches diameter was cut from a piece of sheet iron , and ground down to a thickness which must have been about ^th of an inch , as the prepared disc was found to weigh 114 grains . Two stout copper electrodes were soldered to its circumference at opposite points . A point at 90 ' on the circumference from one of these was taken , and at about ^th of an inch on each side of it were soldered the ends of a piece of No. 18 copper wire two yards long , to serve as a multiplying branch . The 5 f2 disc was put on a copper cradle covered with paper , supported between the flat poles of the Ruhmkorff electro-magnet , with the line joining its principal electrodes at an Fig. 57 . angle of 45 ' to the magnetic axes of the field , and a current from a large single element of Daniell 's was sent through it by these electrodes . One electrode of the galvanometer was applied to the middle of the multiplying branch , and the other was moved about on the opposite parts of the circumference of the disc till a position giving no current was found , where it was then soldered . The moveable electrode applied to different points of the multiplying branch was then found to give sensible galvanometer indications with a motion of a quarter of an inch , and after a very short time the zero-point became tolerably steady . The electro-magnet was then made , with Fig. 58 . the galvanometer circuit broken , and when it was closed again a decided indication of a current was observed in the galvanometer . This current was checked by sliding the moveable electrode towards the end of the multiplying branch next the equatoreal part of the magnetic field ; and the conclusion was , that the conducting power of the plate , when magnetized , became greater across than along the lines of magnetization , which was confirmed by every repetition and variation of the experiment . Now it is obvious that the intensity of magnetization must have been on the whole greater in the parts of the disc next the poles : hence a diminution of conductivity across the lines of magnetization , to the same extent as that which we know from Experiment 1 . exists along them , would give a contrary effect to that now observed ; and it follows that the electric conductivity is in reality greater across than along the lines of magnetization in magnetized iron . 177 . This experiment was witnessed by Mr. Joule , and afforded a full confirmation of the conclusion ( ^ 172 ) which had been established by Experiment 5 . above , and which follows from Experiment 1 . and Experiment 6 . , considered together . The effects of applying pieces of hot wood equatoreally or axially to the disc were very clearly observed , and were always similar to those described above ( S 166 ) , indicating a greater resistance to the parts of the current crossing the hot region than to those passing through the comparatively cool parts of the iron . wire , with a sudden reversal of the current . Sometimes the incandescence was assisted by a spirit-lamp flame applied to the middle part of the wire , and the ends were kept cool by wet threads . Sometimes in a long wire with a current through it not quite strong enough to keep it at a red heat , a small part was made incandescent by a slight application of heat as nearly as possible at one point , by a spiritlamp flame . Still there was never observed the slightest motion of the incandescent part , when the current was suddenly reversed , and I concluded that whatever had been observed in the way of different heating effects of the positive and negative electrodes , must have been owing to peculiar agencies of the current in passing between metal and rarefied air , or to some other cause than thermal convection in metals ; and I saw that more powerful tests would be required to bring out the result I looked for . 20 . I next made experiments on a conductor of bar iron bent into two equal upward vertical branches on each side of the horizontal part , which was kept immersed in a vessel of hot oil , while the upper ends of the vertical branches were kept cool by streams of cold water . Vessels of water were applied round the two vertical branches , as calorimetrie arrangements to test heat evolved or absorbed in them by the agency of a current sent down one and up the other from a nitric acid battery of sixteen small iron cells , arranged as a single element . The current was sent first for half an hour in one direction , then half an hour in the contrary direction ; and so on , with a reversal every half-hour . The water round the two vertical branches was kept constantly stirred , and thermometers in fixed positions in them were observed at frequent intervals during the experiments , which were each continued for about two hours . A comparison of all the readings taken showed a rather higher mean temperature in the branch down which the current was passing than in the other ; indicating , differentially , a cooling effect in the branch through which the current passes from the hot middle , and a heating effect in the other . This experiment appeared to show that " the resinous electricity " carries heat with it in an iron conductor ; but the irregular variations of temperature in each thermometer were so much greater than the differential effect deduced , that I could not consider the conclusion satisfactorily established . SS21 to 29 . Unsuccessful attempts with large bar conductors . 21 . There were difficulties connected with the arrangements of the calorimetrie vessel , which made me judge that it would be better , instead of testing the average temperature of two portions of the conductor , each extending the whole way from the hot middle to the cold ends , to simply test the temperature of as nearly as possible one point midway between the hot and cold on each side ; and it appeared that the heating could be more easily applied and better regulated by a source of heat at the middle of a straight horizontal conductor , than by the plan I had followed in the arrangement just described . I therefore got bars of copper and iron , with holes to admit the bulbs of sensitive thermometers , made to the following dimensions : Copper conductor . Iron conductor , inches . inches . Whole length ... 16 24 Breadth ... . . 12 Depth 2 ' 3 Depth of hollows. . 2^ 2 ' Diameter of hollows . ^\#163 ; These relative dimensions were chosen so that the conducting powers of the two bars for electric currents , and consequently for heat also , might be not very unequal . A vessel of tin-plate , perforated to admit the bar through its sides , was soldered round the middle of each conductor , and two others so as to leave about 2 inches at the ends of the conductor projecting beyond them . The parts of the conductors within these vessels were about 3 inches long in the copper and A ' inches in the iron , and the parts between the middle vessel and the vessels at the two sides were 2 ' and 2 inches respectively . The bores for the thermometer bulbs were exactly in the middle of the last-mentioned parts . In experimenting on either conductor , the central vessel was generally filled with oil or water , and kept hot by a gas-lamp below it . Streams of cold water from the town supply-pipes were kept flowing through the two lateral vessels . 22 . To make these streams constant , whatever variations of pressure might occur in the supply-pipes , a cistern in a fixed position above the conductor was kept full ( overflowing ) , and the coolers were supplied by pipes from this cistern . The supply often failed for several minutes , and sometimes for much longer ; and after an experiment ( Nov. 19 , 1853 ) was nearly lost from this cause , a plan was arranged to lift water up from a larger cistern ( into which the exit-streams from the coolers were discharged ) , and to pour it into the smaller cistern above , so as to keep the stream constant in quantity ( although not quite invariable in temperature ) even when the proper supply failed . 23 . A galvanic battery for exciting a current through these conductors was prepared , consisting at first of four , and ultimately of eight , large iron cells , each measuring internally 12 inches deep , 10^ inches broad , and 2 ' inches from side to side ; eight porous cells , each 12 inches deep , 10 inches broad , and 2 inches from side to side ; and eight zinc plates , each 9^ inches by 10 inches . The iron cells were charged with a mixture of nitric acid two parts ( bulk ) , sulphuric acid three parts , and water two . The porous cells were charged with dilute sulphuric acid . In each of the cells there were ' ' square feet of zinc surface exposed to 1 ' square feet of iron , and the electro-motive force was not far from double that of a single cell of Daniell 's . 24 . After preliminary experiments in which , with oil in the central vessel kept hot by a gas-lamp , the temperatures were too unsteady to allow any results of value to be obtained , water was substituted for oil in the central vessel , and was kept boiling briskly by the gas , the place of the water evaporated being frequently supplied by small quantities of boiling water poured in , so that ebullition never ceased . The irregularities having been found to be much diminished , experiments were made in the following manner , 25 . Four of the large iron cells , arranged as a single galvanic element , were used to excite the current . The experiment lasted about two hours , during which the current was sent through the conductor for twenty minutes at a time , alternately in the two directions , twice in each direction . Several minutes were spent in changing the direction of the current ; the stiffness of the electrodes , and the clamps used for the connexions which had to be changed , rendering the process very troublesome . Readings of the thermometers were taken at intervals of five minutes during the flow of the current in both directions , as well as for some time before the current commenced and after it ceased . 26 . The results of this experiment manifested , among great irregularities in the indications of the thermometers , a very decided differential variation between the two every time the direction of the current was changed ; and appeared so promising , that a series of further experiments on the same copper conductor , and on the iron conductor similarly arranged , were immediately commenced , for the purpose of testing decisively the conclusion which had been indicated , and for discovering the corresponding effect in iron . To avoid the loss of time and the derangement in the position of the conductor by the shifting of the heavy clamps and stiff electrodes between its ends , in changing the direction of the current , a commutator , by which the change could be effected nearly instantaneously , was constructed on the following plan . 27 . Four square holes , each of 1 inch , in a square block of mahogany , were fitted Fig. 1 . with bottoms of thick copper slabs , passing through the mahogany , and cemented with red lead so as to hold mercury , which was poured into each hole . The copper slabs projected outside to distances of about an inch , and each bore a bundle of 100 No. 18 copper wires soldered to it , two of which , connected with diagonally opposite , copper slabs , served as battery electrodes , while the other two were clamped to the ends of the conductor to be tested . The four slabs have only to be connected by two conducting arcs parallel to one pair or to the other of the sides of the square , to send the current one way or the other through the conductor ; which was done by means of two heavy brass castings , as shown in the diagram ( fig. 1 ) . This commutator has been used in a considerable variety of experiments , and has been found very convenient . It gives the means of reversing almost instantaneously a very powerful current , without the necessity of bending any of the electrodes or deranging any part of the apparatus , and the conductors involved in it are so strong that it occasions very little resistance . 28 . As the supposed differential effect had appeared not to be increased after the first five minutes of the flow of the current in either direction , shorter periods of various lengths were tried , and more frequent observations of the thermometers were made , for the purpose of discovering the gradual variation of the temperature in the conductor , towards its final distribution as affected by the current . Four more large iron cells were added to the battery , which made it consist in all of eight cells , arranged as a single galvanic element , exposing 20 square feet of iron to 10^ square feet of zinc surface . As the strength of current thus produced would be nearly double of that given in the previous experiment , any true effect of the kind sought would be augmented in the same ratio ; and might be expected , both on this account and because of the improved system of observation , to become much more decided . These expectations , however , were not borne out by the results . The irregularities certainly became much diminished , but with these the differential effect on the thermometers , following the reversals of the current , either quite disappeared , or became very much less considerable than that which had been observed in the first experiment , and which I afterwards was led to attribute to some derangement in the position of the conductor occasioned by shifting the heavy clamps and stiff electrodes from between its two ends , causing the thermometer bulbs to alter a little in their positions in the hollows . 29 . Many experiments , both on the copper and iron conductor , were made , from October 1852 to March 1853 , and the results of the observations ( on each of the two principal thermometers either every half-minute , or every quarter-minute , during an experiment of about two hours ) carefully reduced ; with much labour at first when arbitrary scale thermometers were employed , but afterwards with far greater ease when centigrade thermometers , constructed for this investigation at the Kew Establishment , were received and brought into use . In the months of September and October 1853 the investigation was taken up again . The thermometric observations which had been made in the previously completed experiments , were all reduced , on the plan of the Tables given ( SS 47 and 56 ) below for subsequent experiments , and , when thus tested , they appeared to contain some indications of the effect looked for . Several more sets of observations of the same kind were therefore executed , but with various modifications of details . Still no decided result could be obtained , and I concluded from all the experiments which had been made , that the anticipated effect must be too small to be discovered without either increasing the sensibility of the test or diminishing the irregularities . I therefore prepared new apparatus , by which the former , and as much as possible of the latter object , would be attained . SS 30 to 34 . Improvements and Modifications of Apparatus . 30 . Instead of increasing the power of the battery , which I reserved as a later resource , if necessary , or of increasing the length of the conductor between the heater and the coolers on each side , which , while it would increase in the same ratio the amount of the effect looked for , would increase in a duplicate ratio the time that would have to be given to allow it to reach a stated proportion of its limiting value , I had conductors made of about the same length as the others , but of considerably less section . 31 . With a view to perfecting and testing the action of the heater and coolers , each conductor was made up of a number of slips of flat sheet metal , bent and placed together , as shown in the accompanying diagram ( fig. 2 ) . The slips were held firmly Fig. 2 . Fig. 3 . together by a vice , while collars of sheet copper , separated from them by vulcanized india-rubber , were soldered round them in the places for the sides of the heater and coolers . Tin-plate vessels , as shown in the diagram , were then put together , and soldered to these collars . The interstices between the slips and the india-rubber , and 4 s2 the metal collars round the india-rubber , were stopped with red lead , and after some trouble were made water-tight . Thus the heater and coolers , without any metallic communication with the conductor , served the purpose of keeping the required supplies of hot and cold water round it in the proper places . The spaces for the thermometers were firmly stopped below with corks fitted to support the lower ends of the bulbs in perfectly fixed positions ( fig. 3 ) . Little collars of cork were put round the tubes just above the bulbs , and pushed down into the upper end of the hollow so as to hold the thermometers firmly and prevent all motion of their bulbs . 32 . Various methods of heating the central part of the conductor were tried . First , as in previous experiments , water in the central vessel was kept boiling either by a gas-lamp under it , or by steam blown into it from a separate boiler ; then a complex system with a boiling fountain , by which I attempted to get a perfectly uniform stream of water at a constant temperature , as little short of boiling as possible , to flow through the open spaces between the different slips within the central vessel , was used during several experiments . Lastly , water filling the central vessel was kept at a very constant temperature , near the boiling-point , by a gas-lamp below it , regulated by a person watching the indications of a thermometer with its bulb fixed in the middle space between the slips , as nearly as possible in the centre of the compound conductor . This last I found to be by far the best plan , and I used it in all subsequent experiments in which any external application of heat to the conductor was required . 33 . Each cooler was divided into four compartments by partitions of tin-plate , stopping all communication from one to another , except through the spaces between the different slips composing the conductor . A constant stream of cold water ( S 22 ) , introduced by the compartment nearest to the middle of the conductor , and drawn off by an overflow pipe , from a compartment next the end , was thus forced to flow all through among the different slips , and , as I found by placing thermometers in various positions in each compartment , gave a very satisfactory effect in fixing the temperature of the whole section of the conductor . 34 . The experiments were made in other respects exactly as described above ( SS 28 and 29 ) ; the electric current , however , not being often again kept up for a longer time than ninety-six minutes , since the fumes , which always began to rise from the battery after the current had been flowing for about an hour , began after half an hour more to occasion great irregularities and inconvenience by causing the liquid ( which sometimes became very hot , ) to foam and overflow in some of the iron cells . The atmosphere had been in previous experiments sometimes rendered intolerable for the observers , by the acid vapour ; but this evil was done away by covering the battery with cloths kept moist with ammonia and water , and by moistening other surfaces in the neighbourhood in the same way , so that the fumes never got far without meeting vapour of ammonia and combining into white clouds , which were perfectly innocuous . to 38 . First Experiments with Multiple Sheet Copper Conductor . 35 . The copper conductor on the new plan was first used in an experiment on the 28th of October , 1853 ; with the central vessel heated by steam , and a current from the eight large iron cells kept flowing for seventy-two minutes , alternately in contrary directions , six times six minutes each way . The thermometers were noted every halfminute . The observations thus recorded , when thoroughly examined , indicated a slight differential cooling effect in the part of the conductor in which the nominal current was from cold to hot , and a heating effect where it passed from hot to cold ; that is to say , a convection of heat in the nominal direction of the current , or as I shall call it to avoid circumlocution , a convection of heat by vitreous electricity . 36 . A second experiment with the same conductor was made on the 2nd of November , 1853 , in which the current was kept flowing for ninety-six minutes , eight times six minutes each way , and the thermometers were noted every quarter-minute . An examination of the recorded results indicated still the same kind of effect , but to a much smaller extent . Thus the final average , for the alteration of difference , between the temperatures at A and B due to the flow of the current for six minutes in one direction , after it had been flowing for six minutes in the contrary direction , amounted to -039 ' Cent , in the first experiment , and to only #0143 ' in the second experiment . A full analysis of the progress of the differential variation of temperature during the flow of the current is given in Tables I. and II . , S 56 below , and shows through what fluctuations the final alterations are reached . The temperatures , at the ends of the successive times of flow in one direction or the other , and the evaluation of the mean final effect , are shown , for each experiment , in the following abridged Tables . 37 . The observations made during the first period ( that is the time from starting till the second reversal of the current ) are rejected from the average in every case of experiments on the new conductors , because they were found to show so great absolute elevations of temperature ( due to the frictional generation of heat by the current ) that no alteration of difference between the thermometer observed during them could be relied on as an effect depending on the direction of the current . to 43 . Decisive Experiments with Multiple Sheet Iron Conductor . 39 . These experiments seemed therefore on the whole to establish a probability in favour of the convection of heat by the so-called positive electricity , when a current is kept up through an unequally heated conducto ? . The convective effect , if of this kind , ought ( S 18 ) to be less in iron than in copper , I therefore had little expectation of finding an indication of it in the iron conductor which ( S 31 ) had been in the course of preparation ; but as soon as it was ready for use I made the following experiments , and was much surprised by the result , which became manifest before the first of them was finished . 40 . Conductor composed of thirty slips of sheet iron . Experiment HI . November 12th , 1853 . ( Current six times eight minutes in each direction . ) Temperatures and Augmentations of ! differences of temperature after eight minutes of current entering differences from By end next A. By end next B. periods . Periods . TA . TB . TB-TA=D . TA . TB . TB-TA=D ' . D'-D . i I. 51-43 ! 53-56 2-13 51-48 53-49\#163 ; '01 -12 II . 51-62 | 53-30 1-68 51-41 5321 1-80 -12 III . 51-73 | 53-26 1-53 52-03 53-87 1-84 -31 IV . 52-01 I 53-80 1-79 51-32 53-42 2*10 -31 V. 51-30 53-00 1-70 51-00 52-95 1*95 -25 VI . 51-14 52*98 1-84 50-69 52-80 2-11 -27 Means for five periods. . 51-56 53-268 1-708 51-29 53-25 1-96 -252 Augmentation of difference during periods included ... -10 Deduct average augmentation per half-period -010 Effect due to reversal of current 0'-242 , : . in favour of Resinous Electricity . Experiment IV . November 19th , 1853 . ( Current seven times eight minutes in each direction . ) Temperatures and Augmentations of differences of temperature after eight minutes of current entering . J^11 ? 68 < ? " * f By end next A. By end next B. periods . Periods . TA . TB . TB-TA=D . TA . TB . TB-TA . D'-D . I. 57-50 59-30 1-80 58-02 59*84 1-82 '-02 IL* 48-20 51-15 2-95 1 46-82 49'79 2-97 -02 III . 46-49 49-13 2-64 I 47*01 49*95 2'94 -30 IV . 48-41 51-69 3-28 48-31 51-99 3-68 -40 V. 48-36 51-74 3-38 48-18 51-80 3-62 -24 VI . 48*00 51-20 3-20 48-00 51-49 3-49 -29 VII . 48-31 51-51 3-20 48-06 51-60 3-54 -34 Means for five periods. . 49-3243 52-2457 3-14 49-20000 52-35143 3-454 -314 Augmentation of difference during periods included ... 0-57 Deduct average augmentation per half-period -057 Effect due to reversal of current 0'-257 , in favour of Resinous Electricity , 41 . A full analysis of the differential variations throughout each of these experiments , derived from observations of the thermometer taken every quarter of a minute , was made in each case immediately after the conclusion of the experiment ( see Tables I. and II . S 47 below ) , and was sufficient to convince me that the true effect in the iron conductor is of the kind indicated by the preceding summary of the effects apparent at the ends of the periods . 42 . To try whether or not the very considerable effect thus discovered depended on some inequality in the conductor itself , I made an experiment on the 25th of November 1853 exactly like the two preceding , with the exception that the middle vessel previously used as a heater was filled with cold water at the commencement . The current was sent six times eight minutes in each direction ; the thermometers were noted every quarter of a minute ; and the observations were reduced and compared in the usual way . The result gave no effect of the kind observed in the preceding experiments , but ( probably because of a temporary failure in the water-supply for the coolers ) showed , on the contrary , a deviation in the mean difference of temperature amounting to O#029 Cent. , being about a tenth part of the amount of that effect , but in the opposite way according to the direction of the current through the conductor . Before the experiment was concluded boiling water was poured through the central vessel and left filling it , but with no lamp below . The two thermometers ( A and B ) being thus raised to about 27 ' Cent. , the current was again started and was sent through the conductor for three times four minutes in each direction . The thermometers rose each nearly 2 ' , but fell again by nearly 5^ ' before the conclusion . The mean differential result , whether from these three periods ( amounting to '*05 Cent. ) , * Rejected because of a failure in the water-supply through the coolers during the whole of Period I. or from the last two of them without the first ( O#025 Cent. ) , was of the same kind as in the first two experiments . This experiment then conclusively demonstrated that the effect previously discovered was really owing to the heat in the central part of the conductor , and not to any inequality in the metal of the conductor itself , nor to any accidental disturbing agency . 43 . It was thus established , that the Resinous Electricity carries heat with it in an iron conductor . SS44 and 45 . Experiment with Copper Conductor , repeated . 44 . The very small effect I had discovered of the opposite kind in the copper conductor required confirmation ; and indeed the analysis of the progress of the variation ( see Tables I. and II . S 56 below ) was so unsatisfactory , that I felt it quite an open question , whether it was the true effect , or merely an accidental coincidence of irregularities ; and I thought it improbable that contrary effects should really exist in copper and in iron . I made on the 26th of November another experiment on the copper conductor , with the current flowing six times eight minutes each way ( instead of eight times six minutes , as before , because the analysis seemed to show that the effects which had chanced to appear in the average results of the six minutes might disappear with longer periods* ) ; but I got still a very small result of the same kind . The full analysis ( Table III . ) was equally unsatisfactory with those of the two preceding experiments on the same conductor . The following numbers show the temperatures at the reversals , and the final result , as in the previous abridged tables . 45 . Conductor composed of thirteen slips of sheet copper . Experiment V. November 26 , 1853 . ( Current six times eight minutes in each direction . ) Temperatures and Dimmutions differences of temperature after eight minutes of current entering from 'dd ? ^t Periods . By end next A. By end next B. ends of periods . TA . TB . TB-TA=D . TA . TB . TB-TA=D ' . D'-D . I. 50-88 51-78 1-90 50-88 52*72 1#92 '*02 II . 50-64 52-49 1-85 50-53 52*32 1-79 + *06 III . 50-38 52-29 1*91 50-01 52-00 1-99 -08 IV . 50-14 52-08 1-94 49*90 51-83 1-93 +-01 V. 49-60 51-61 2-01 49*48 51-52 2-04 -03 VI . 49-11 51-22 2-11 48-80 50*92 2-12 -01 Means for five periods 49'974 51938 1-964 49*744 51-718 1-974 --01 Augmentation of difference during periods included ... -20 Add average augmentation per half-period + 0*02 Effect due to reversal of current -01 , in favour of Vitreous Electricity . *I now believe that a true effect , amounting to from '*01 to '*02 , was really reached in three or four minutes , and that in the latter parts of the half-periods there was no sensible augmentation of this effect , but Another experiment was also made on the new iron conductor , and results as decisive as those in the first two experiments were obtained . The following abridged Table shows sufficiently the character of the effect demonstrated ; and the analysis of the progress of variation is given in the full table ( Table III . S 47 ) below . Experiment VI . December 2 , 1853 . Conductor composed of thirty slips of sheet iron . ( Current six times eight minutes in each direction . ) Temperatures and Augmentations differences of temperature after eight ' minutes of current entering ' . ot dl\#187 ; |prences ' ' from . middles to Periods . By end next A. By end next B. ends of periods . TATB . TB-TA=D . TA . TB . TB-TA=D ' . D'-D . I. 54-76 oe-33 i-57 54-80 56-66 1-86 '-29 II . 54-97 56-68 1*71 54-89 56-80 1-91 -20 III . 55-01 56-70 1-69 54-93 56-86 1-93 -24 IV . 55-22 56-90 1-68 55-08 57-10 2-02 -34 V. 55-31 57-08 1-77 55-07 57*12 2-05 -28 VI . 55-12 57-00 1-88 54-84 57-03 2-19 -31 Means for five periods 55-126 56-872 1-746 54-962 56-982 2-020 -274 Augmentation of difference TB TA during included periods -33 Deduct average augmentation per half-period #033 Effect due to reversal of current 0'-241 , in favour of Resinous Electricity , 47 . The following Tables show the progress of variation of the difference between the temperatures of the two tested localities ( A , B ) of the iron conductor , during each of the three regular experiments referred to above , as derived directly from the quarter-minute or half-minute observations actually made in the course of each experiment . only irregular fluctuations , sometimes counteracting and reversing the true effect , but generally only diminishing it and increasing it alternately , and always maintaining , during the whole latter half of the aggregate of the half-periods , an average deviation of the kind noted as the final result . A careful consideration of the Tables I. , II . and III . given below , S 56 , for the copper conductor and of their graphical representation ( see Diagram , S 57 ) , is , I think , sufficient to establish this view . [ April 9 , 1856 . ] The gradual augmentation of the difference TATB from its value at a time when the current had been flowing for eight minutes entering by the end next B , consequent upon reversing the current and letting it flow continuously entering by the end next A , is shown by the numbers at the foot of each table , as a mean result derived from a single experiment . The mean of the results of the three experiments is shown by the following numbers , and is exhibited by a curve in the Diagram ( fig. 4 ) of S 57 below . Current entering by end next A. Time from instant 1I ill of reversal in quarter-^ 012345678 9 10 11 12 13 14 15 16 17 18 19 2021 222324 2526 27 28I29 3031 32 minutes J Mean Auerraenta-1 " ^ ^ *\#171 ; '* > . *o\#161 ; us oo\#169 ; \#187 ; o co t > . *o\#171 ; \#187 ; o co io w * > . non of difference ^ooohco^iocooioihnw^iisionooxoiohhhoi^nwww^ii^ TATB J ? ? ? ? ? ? ? ? ? ? ? ?9 > ? > ? ? ? ? ; T < TIT'THT'T*7ITH7^7 < ^^^^^^^ < ^^ < ^(^ < ^ < ^ 49 . That Vitreous Electricity carries heat with it in copper is indicated by each of the three experiments on the thirteen slip conductor adduced above , but by so narrow an effect ; amounting on an average to only 0'*02Cent . , which corresponds to a reading of half that amount , or xtro^h 'f a degree , being y^-th of a division on the scale of each thermometer ; with such discrepancies among the results of the different experiments ( Oct. 28th , effect -039 , Nov. 2nd , -0143 , Nov. 26th , -01 ) ; and with so great fluctuations in the course of each experiment ( see Tables I. , II . , III . , S 56 below ) ; that I did not venture to draw from them so seemingly improbable a conclusion , as that the convective effects in copper and in iron should be in contrary directions . The dynamic theory ( S 18 ) was fully satisfied by the demonstration which the experiments gave , that the convective effect is undoubtedly in iron a conveying of heat in the direction of the Resinous Electricity , and that it is less in amount in copper , whether in the same direction as in iron or in the contrary direction . But it was still an object of great interest , ( in fact an object of much greater interest than any verification of conclusions from the dynamic theory , which were in reality as certain before as after the experiments directly demonstrating them , ) to ascertain the actual nature of the convective effect in copper , and I therefore endeavoured to make more decisive experiments for discovering it . 50 . The three experiments which had been made were quite sufficient to prove that the convective effect , whatever its true nature might be , was nearly insensible to my thermometers without either more powerful currents or a more sensitive conductor . To work with more powerful currents would have increased immensely the labour of carrying out the experiments , and would besides involve a large addition to the battery which had been used hitherto . I preferred therefore to make the conductor more sensitive , which I saw could be done by diminishing the body of metal in the tested parts , and so preventing the looked-for thermal effect from being so much conducted away from the localities of the thermometers as it had been . I accordingly had several slips of copper cut away from each side of the conductor in the parts between the heater and the coolers , leaving the parts within these vessels unchanged . 51 . Several experiments were made on the conductor thus reduced successively to smaller and smaller numbers of slips ; but the results did not appear much more decided than they had been in the experiments on the unreduced conductor , until it was tried with all the slips but two cut away . Thus with four slips left , the following results were obtained : 52 . Copper conductor reduced to four slips . Experiment VII . February 1854 . ( Current six times eight minutes in each direction . ) Temperatures and ^"f111 ! 111* ? ? ? ?1 ? 'f differences of temperature after eight minutes of current entering . , \#8222 ; , By end next A. By end next B. periods . Periods . TA . TB . TA-TB = D. TA . TB . TA-TB=D ' . D'-D . I. 4 & -00 45-24 -76 45-92 45-27 -65 --11 II . 45-82 45-19 -63 46-01 45-43 -58 --05 III . 4600 45-50 -50 46-02 45-54 -48 -02 IV . 46-20 45-77 '43 ' 46-21 45-76 -45 j -02 V. 46-18 45-80 -38 ! 46-09 45-71 -38 | -00 VI . 46-09 45-72 -37 | 46-05 45-68 -37 *00 Means for five periods. . 46-058 45-596 -462 | 46-076 45-624 -452 -010 Diminution of difference during periods included -28 Add average diminution per half-period +'038 Effect due to reversal of current '018 , in favour of Vitreous Electricity . The effect shown here is of the same kind as had been found in all the previous experiments , but was still too small to be very satisfactory . Some unknown cause made the difference TATB to diminish so much through the whole experiment as to overpower the apparent tendency of the current from B to A to increase it , and the abridged table has on this account a very unsatisfactory appearance as regards the conclusion drawn from it after the proper correction for their diminution is applied : but the full examination of the progress of variation in the course of the experiment shown in Table IV . below is much less unsatisfactory , and shows undoubtedly the true convective effect in copper . 53 . The following results , derived from the first experiment made on the conductor reduced to two slips , show a very marked increase in the effect , and make the result quite apparent even without the full analysis given below in Table V. mdccclvi . 4 u The Bakerian Lecture . On the Electro-dynamic Qualities of Meta is* . By Professo ! * William Thomson , M.A. , F.R.S. Received February 28 , Read February 28 , 1856 . 1 . An electrified body may be regarded as a reservoir of potential energy , and any material combination in virtue of which bodies can receive charges of electricity is a ource of motive power . The development of mechanical effect from the potential energy of electricity , or through electric means from any source of motive power , may take place in a great variety of ways . For instance , electro-statical attractions and repulsions may become direct moving forces ( as in " Franklin 's Spider " ) , to do work in the discharge of an electrified conductor or in the continued use of a continuous supply of electricity ; or the forces of current electricity may , as in any kind of electro-magnetic engine , become working forces on bodies in motion ; or the whole energy of the discharge may , as discovered by Joule , be converted into heat , which again may be transformed into other kinds of energy ; or the heat evolved and absorbed by electricity , in a circuit of two different metals , at the places where it crosses the junctions from one metal to the other , being a thermal result of dynamic moment^ when the junction at which heat is evolved is at a higher temperature than the junction at which heat is absorbed , maybe used in a tbermo-dynamic engine . Again , a thermo-electric current is a dynamic result derived from a definite absorption of heat in one locality and a definite evolution of heat in a locality of lower temperature . 2 . Of these various kinds of action , all except the first mentioned , depend essen* The author has to acknowledge much valuable assistance in the various experimental investigations described in this paper , from his assistant Mr. McFarlane , and from M. C. A. Smith , Mr. R. Davidson , Mr. F. Maclean , Mr. John Murray , and other pupils in his laboratory . t Either an evolution of heat at a temperature higher , or an absorption of heat at a temperature lower , than that of the atmosphere , may be taken advantage of to work an engine giving mechanical effect from heat ; by using the atmosphere in one case as a recipient for discharged heat , in the other as the source of the heat taken in . Or an evolution of heat at any temperature and an absorption of heat at any lower temperature , may be taken advantage of for the same purpose , in a limited material system , neither taking heat from nor parting with heat to any external matter . Hence such a double thermal effect may be said to possess " dynamic moment . " See the author 's " Account of Carnot 's Theory of the Motive Power of Heat/ ' SS 4 to 11 , Trans. Roy . Soc. Edinb . Jan. 2 , 1849 ; also his " Dynamical Theory of Heat , " SS 8 , 13 , 23 to 30 , Trans. Roy . Soc. Edinb . , March 17 , 1851 , and " Dynamical Theory of Heat , Part VI . Thermo-electric Currents , " S 102 , Trans. Roy . Soc. Edinb . , May 1 , 1854 . The series of articles under the general title " Dynamical Theory of Heat , " have been republished in a succession of Numbers of the Philosophical Magazine , viz. SS 1 to 80 , Vol. July to Dec. 1852 ; SS 81 to 96 , Vol. Jan. to June , 1855 ; SS 97 to 181 , Vol. Jan. to June , 1856 . After this experiment I considered it quite established that the Vitreous Electricity carries heat with it in copper . 55 . The conductor was still further diminished in breadth ( so as to be only an inch broad in the parts between the heater and coolers on each side ) , and an experiment was made before my class on the 19th April , 1854 , leading to the following results , shown as in the abridged tables of the preceding experiments . Experiment X. April 19th , 1854 . Copper conductor of two slips , further diminished in breadth . ( Current seven times six minutes each way . ) Temperatures and Diminutions of differences of temperatures after six minutes of current entering amerences\#8482 ; m By end next A. By end next B. periods . Periods . TA . TB . TB-TA=D . TA . TB . TB-TA=D ' . D-D ' . I. 74-30 7 & -60 1-30 74-81 77*50 2-69 --39 II . 73-80 76-48 2*68 75-32 78-10 2-78 -'10 III . 76-25 79-42 3-17 76-17 79-18 3-01 -16 IV . 76-33 79-51 3-18 76-28 79'37 3-09 -09 V. 75-60 78-69 3-09 75-20 78-07 2-87 -22 VI . 74-80 77-70 2-90 75-00 77'75 2-75 -15 VII . 74-10 76-84 2-74 75-42 78-20 2-78 --04 Means , Period I. off ... 75-147 78-107 2-96 75-565 78-445 2-88 -08 Augmentation of differences during periods included ... -09 Add average augmentation per half-period -0075 Effect due to reversal of current '-0875 M^TnT8 > PJri0dsLandi 75-356 78-36 3-004 I 75-594 78-494 2'90 -104 VII . off J Augmentation of differences during periods included ... -06 Deduct average augmentation per half-period *006 Effect due to reversal of current '110 The effect here obtained , although of quite a decisive character , does not appear to show any increased sensibility resulting from the further diminution in the breadth of the conductor . 56 . The following Tables [ printed after apart of S 58 ] show a complete analysis of the results of the seven experiments on the copper conductor which have been adduced . 4u 2 The average progress towards the final effect of a reversal , as indicated by the numbers at the ends of these Tables , is exhibited graphically for the copper conductor in the different states in which it was used in the experiments , in the following Diagram , along with the curve exhibiting the corresponding reverse effect in the iron conductor . The uppermost curve represents the results of three experiments with the Iron conductor ( thirty slips ) , the points marked # representing the mean of three days ' observation , and the points marked -.that of two days ' observation . The lowest curve represents the results of three experiments with the Copper conductor ( thirteen slips ) , the points marked V denoting three days ' , and the simple dots . two days ' observation . The middle curve represents three experiments with the Copper conductor ( two slips ) , the points marked O denoting the mean of three days ' observation . Fig. 4 . Tff I11111I LL1 11111111 -I^Kitddbfaja : %f 3 & ^TI2l1Z ^s i -M i zz zz znzz~iizzzin sf zz zn zn zz nz zz nizzznzn ZI ' . I / ' ? '\#187 ; " - ; , I -_i _ mmm m^ ^^ ^^ ^^\#187 ; .\#187 ; ^mi\#171 ; . < \#191 ; 2_._ -i m.__ __ __ _ __ _ __ , _ __ 1 _ . zzzuzz zz zz zzzz zz zz zz zz zz zz zz zz zz zn~ zz zz zzzz zz iziz zz zz zz zz ^z zzi zz zz zn zz / zz zzz zz zz zzz ' ~^_ ^2 zi zz zi izi zz zz zz zz zz azz=zzzzzz=zzzzzz^zzzzzzzzzizz^^^^^:r=:z:zzizzzizzzz ~~ a~"":"":~"1 yk " z^^r t ~~ AS tg\#191 ; ^ " / ZZZZ ! Z ] E^IZI ZZ ZZ ' ZZ ZIZ ZZ ZZZZ ZZ ZZI ZZ HZ ZZ / / ^ ^z ZZ ZZ ZZ ZZ ZZ ZZ IZZ ZZ ZZ ZZ i ~^_ ~^_ e " ^2 . ZZ ZZ j s^ ZZZZ HZ ZZZZ IH IH ZH ZZ ZH ZZ ZZ ' ZH ZZ HZ . IH / jr x\#187 ; ^3 ZZ ZZ I ~/ ^\#8482 ; ^^ ^MM"* m^ ^Ml ^z ^z ^^ ^l"*1^ 1 \#191 ; i^kZ HTH ^UH ZZIHZr3_"~HZHZZHH:~~~HziElZ ! ^~~^S^S^^^ = ^^^^^^ j\#191 ; _ m '_ ^[ .=:m:izz^iH 1 ^ ' : nzzzzz 58 . The diminution of the conducting power in the copper conductor had so markedly augmented the looked-for indication of a convective effect , that it was to be expected a corresponding augmentation might be obtained by treating the iron conductor similarly . Instead , however , of cutting up the iron conductor , which , as it stood , possessed sensibility enough to give a very decided result , I prepared a new iron conductor on a much smaller scale . It appeared that the smaller the conducting power for the same strength of current , and the same difference of temperatures between hot and cold , the greater would be the indication of convective effect ; and the greatest indication would therefore be obtained by [ Continued after Table VIL ] tially on certain definite properties of matter in regard to which different metals have remarkably different qualities . Thus in electro-magnetic engines the electric conductivity of the coils through which the current passes , and the magnetic inductive capacity and retentiveness of the iron cores of the electro-magnets , are essentially involved ; and as essentially , when permanent magnets are used , the magnetic properties of steel , loadstone , or other bodies possessing strong retentiveness for magnetism . In the simple conversion of any kind of energy into heat by means of electric currents in metals , their electric conductivities are essentially and solely concerned . The inverse thermo-electric transformation of energy into an evolution and absorption of heat , at localities of different temperature , in quantities differing from one another by the thermal equivalent of the work spent in maintaining the current* , depends essentially on certain distinct properties of metals in regard to which their various qualities are shown by the differences of their positions in the thermo-electric series at different temperatures ; and the accessory circumstances of such operations are influenced by the electric and thermal conductivities of the metals used . The same properties are involved in the direct thermo-electric transformation of energy in which electric currents , sustained by the communication of heat in a hot locality and the abstraction of a less quantity of heat in a locality lower in temperature , either produce any mechanical action , or are allowed to waste all their motive power in the frictional generation of heat^ . reducing the conductor so much that the current through it would generate heat enough to keep up the required difference of temperatures without any external heater . 59 . The new conductor was therefore made of just two slips of sheet iron broad enough to admit the whole length of the thermometer-bulbs in the same manner as in the conductor previously used ; these slips were bent in the places for the thermometer-bulbs , but were kept straight and bound close together elsewhere . Guttapercha pipes were cut and cemented upon the iron slips near their ends , so as to lead streams of cold water across them . The part of the conductor between these coolers was packed round with a large mass of cotton wool , the thermometer-bulbs being Fig. 5 . steadied in the apertures prepared for them by means of corks , as before ( S31 ) . The breadth of the conductor was 2 ' inches , the length between the coolers only 3 ' inches ( instead of 10 inches , as in the iron conductors used previously ) , so that too great a time might not elapse before such a nearly permanent state of temperature as depended on the heating effect of the current would be reached . 60 . On the 25th of March , 1854 , an experiment was made with this conductor in the following manner : A constant stream of cold water was maintained through each of the coolers ; a current from the full nitric acid battery of eight large iron cells was sent through the conductor for twelve times four minutes in each direction , that is for ninety-six minutes in all , and the thermometers were noted every halfminute . The actual observations of temperature are required to show the circumstances of this experiment , and I therefore give them as follows ; instead of an analytical table , such as those by which the results of the preceding experiments were exhibited : The differences of temperatures here tabulated , and the half sums of the same temperatures , are graphically represented in Plate XXXV . The result is obvious , either with or without the graphical representation , and affords a striking confirmation of the conclusion first arrived at by so different an apparatus ( S 31 ) , that the Resinous Electricity carries heat with it in iron . 62 . About the same time another form of the experiment was tried on a copper tube , with a vessel of oil fitted round it in the middle , and kept hot by a lamp below it , and with gutta-percha tubes fitted to conduct streams of cold water round it . A current from the battery was sent alternately in the two directions through it , as in the previous experiments , and it was attempted to observe the thermal effects by means of two open thermometer-tubes with small spherical bulbs , pushed into the copper tube from each end , and bent down at right angles outside it , with their lower ends immersed in two cups of spirits of wine . The want of any sufficient regulation of temperature to keep the liquid column of these air-thermometers within range , made it impossible to get any clear indication of a result by this experiment ; but on the whole , there appeared to be an effect of the same kind as had been previously discovered in copper . 63 . A few weeks ago , I began again to make direct experiments on electrical convection with a view to obtaining additional evidence in support of the conclusion which I had arrived at previously , and to investigate methods by which the nature of the quality in other metals could be discovered more readily , and the specific heat of electricity in any metal determined in absolute units . I had determined to give up the use of the nitric acid battery in consequence of the inconveniences which had been alluded to above ( S 34 ) , and accordingly I had constructed a large Daniell 's battery : consisting altogether of eight wooden cells lined with gutta percha , and fitted with sheet copper , suitably arranged with shelves to bear crystals of sulphate of copper ; sixteen porous cells , some of which had served previously in the iron battery ; and sixteen zinc plates of the same dimensions as those previously used . Each wooden cell had sheet copper not only round its interior , but also a portion of the same sheet carried across it so as to divide it into two spaces , each completely surrounded by the metallic surface . A porous cell is put into each of these spaces , and a zinc plate into each porous cell ; the two zincs in the porous cells contained in the same wooden cell being always united . The ordinary liquids of a Daniell 's battery , acidulated solution of sulphate of copper and dilute sulphuric acid , are used . The whole battery power thus consists of eight independent cells , which , with the connexions in ordinary use , may be arranged either in one or in two elements , but which may also , should there be occasion , be readily enough set up in four or in eight elements . Any power may of course be used down to the lowest , with only a single porous cell and a single zinc plate in one of the wooden cells . The sulphate of copper solution is kept constantly in the wooden cells , which remain in a fixed position on a shelf . Electrodes from the large commutator ( S 27 ) , which is fixed to the wall in an adjoining apartment as near as possible to the middle of the wooden cells , are brought through the partition between the two rooms , and kept always ready to be put in communication with the two poles of the battery , however arranged . This battery , or parts of it , have been used in nearly all the experiments described below in Parts IV . and V. , and it has been found very convenient . Some of the wooden cells have contained the acidulated solution of sulphate of copper now for more than a year [ for more than two years now , Nov. 1856 ] , and as yet their gutta-percha linings have shown no signs of injury . 64 . The first of the recent experiments on electrical convection was made with an iron conductor prepared as follows : The conductor , XY , consists of two pieces of thin sheet iron 8^ inches long and f of an inch broad , and bent so that when put together they form three tubular spaces , A , B , C , fig. 6 . The iron is cut so as to make prolongations of these tubes of about Fig. 6 . an inch beyond one side of the conductor . The slips thus put together are soldered so as to make the tubes perfectly air-tight , one end being closed , and the other left open to receive the thermometer-tubes a , b , c , which were cemented air-tight with wax . In soldering , great care was taken to prevent the solder from spreading between the iron slips . Copper electrodes were now soldered to the ends of the conductor , and the junctions were enclosed within pieces of gutta-percha tube , g , h , through which a continuous stream of cold water was made to flow . The distance between the coolers was 7 ' inches , and they were placed so that the four spaces between them and A , B , C were all equal . Divided scales were attached to the tubes , of which the lower ends were immersed in small vessels , A , / , m , containing spirits of wine . The conductor between the coolers was wrapped in a large quantity of cotton wool represented by the space within the dotted line . To send a current through the conductor thus prepared , the whole battery , arranged , as described below , in two elements , each exposing ten square feet of zinc surface to seventeen square feet of copper , was employed : Description and Drawing of Battery with Connexions . R , R and S , S , two series of cells , each containing eight porous cells and eight zinc plates . and D , D , thick copper supports for the zinc plates , the zincs of R , R being firmly clamped to K , K , and those of S , S to D , D. E , E , a thick conductor connecting the coppers of series R , R together . F , F , a similar conductor connecting the coppers of S , S. Fig. 7 . H , H , a bundle of wires connecting the coppers of S , S with the zincs of R , R. M , M , a wooden partition separating the battery-room from the experimenting-room . L and M are two bundles of wire which pass through holes in the partition and connect the commutator G respectively with the coppers of series R , R , and the zincs of series S , S. The bundles of wires O and P complete the circuit through XY , the conductor to be tested . The dotted spaces round the porous cells represent shelves for holding crystals 01 sulphate of copper . 65 . After about an hour and a half , the thermometer at the middle of the conductor indicated 170 ' Fahr. ( 76'7 Cent. ) ; and one of the brass bridges of the commutator was then lifted so as to break the circuit . Immediately the liquid mounted rapidly in each of the three glass tubes of the air-thermometers , and it was prevented from rising above a certain point in the middle one by completing the circuit again . The column of liquid was kept as steady as possible at this point in the middle air-thermometer by a person observing it , and making and breaking the circuit by means of the brass bridge , while two other persons noted the indications of the two lateral airthermometers . The current was reversed every three or four minutes , and the liquid in the middle air-thermometer brought back to the same point , and kept as nearly as possible to it . The imperfection of the regulating system was such as to make it very difficult to prevent great oscillations in the thermometers , but the instantaneous manner in which their indication followed the operations of the break made it certain that the plan would be perfectly successful when a continuously acting regulator should be introduced . As it was , the result afforded a most striking and immediate confirmation of the conclusion previously arrived at regarding the electrical convection of heat in iron . Every time the current was reversed , the liquid fell rapidly ( showing a rise of temperature ) in the thermometer next the end , by which the current nominally entered , and rose rapidly ( showing a fall of temperature ) in the other . Mr. Joule assisted in this experiment , and was satisfied with the evidence it afforded in favour of the conclusion that the Resinous Electricity carries heat with it in iron . 67 . Unsuccessful attempts were next made with tubular conductors of different metals ; and in endeavouring to get decisive results regarding the qualities of copper and brass , I again had recourse to the form of conductor used in the preceding experiment . The new conductors were , however , made of much thinner sheet metal than those of the iron , to admit of a less powerful battery being used ; and consequently , in each case , a frame-work had to be arranged to hold the conductor steady . Great difficulties were met with in continually repeated failures of the air-thermometers . It was therefore found necessary to have metallic tubes continued downwards several inches from the bulbs , so as to prevent the wax by which the glass was cemented from being melted by the heat . The battery , however , had also to be reduced to a single zinc plate in one of the wooden cells , as with more of the battery than this , the heating action had been found to be so sudden in the thin copper and brass conductors , as almost immediately to melt the solder about some of the bulbs , and so make one or more of the thermometers fail before the regulating action of the break was applied . Notwithstanding all precautions , the central thermometer failed in each case , and the action of the lateral thermometers was very unsatisfactory both in the copper and in the brass conductor . The central thermometer could , however , be well dispensed with by regulating by the break one or other of the lateral thermometers ; and thus , after many unsuccessful attempts , experiments were made on copper and brass conductors , which , although still unsatisfactory , showed decidedly the looked-for convective effect . In each case , the thermometer which was not kept to one point by the regulator , always showed an increase of temperature , both in the copper and in the brass conductor , when the current was reversed so as to enter by the end remote from it , and showed a diminution of temperature when the current was again reversed so as to enter by the end next it . Hence it appeared that the Vitreous Electricity carried heat with it in both copper and brass . 68 . The lateral metallic tubes branching down from the conductor to carry the glass tubes of the air-thermometer , constituted a great defect in the plan of apparatus used in the experiments just described ; and the only way of avoiding it appearing to be to make the glass tubes pass through the body of the conductor itself , so as to admit of their being cemented air-tight at its cool ends , I again had recourse to the tubular form of conductor which had been tried unsuccessfully before . 69 . A tube made of very thin sheet platinum , soldered with gold , was arranged in the following manner : A glass rod , 2 ' inches long , wrapped closely round with thin 4 y2 cotton-thread , was pushed into the central part of the tube , in which it fitted closely , and was carefully luted with red lead . After keeping it for several days heated by a stove , gutta-percha coolers , A , A , were fitted on it , leaving a length of 6 inches of tube between them . Wooden troughs , B , B , were then fitted on outside the coolers , and fastened to the ends of a piece of wood , C , C ; straps of thick copper , about an inch broad , were bent to form conducting linings for the troughs , their ends turned round , firmly fastened to C , C , and brought together at D , D , thus forming conFig . 8 . nexions with the electrodes of the commutator ( for this part of the arrangement see also fig. 9 ) . Two pieces of thermometer-tube , bent to right angles , had their short arms rolled with thread , and were pushed into the tube from its ends , as far as\#191 ; , & , leaving spaces ab , ab , each two-thirds of an inch , between them and the stopper aa in the middle of the tube , and made air-tight by cement applied at E , E. The dotted line represents the space round the tube and its wooden stand C , C , filled with cotton-wool . A conducting communication was established between the platinum tube and D , D , by pouring mercury into the troughs ( see also fig. 9 ) . Fig. 9 . 70 . The system of regulating the temperature in one part of the conductor by breaking and making the circuit , had been adopted only as a temporary expedient in the experiment on the iron conductor ( S 65 ) , in consequence of the failure of a continuous regulator which had been fitted up for that experiment . It had the advantage Fig. 10 . of requiring no other apparatus than the commutator , in regular use in all applications of the battery , and it had been found to answer the purpose tolerably well in the first trial . It proved , however , very inconvenient with the finer conductors , from the too great abruptness of its action . Besides , it was open to this very serious objection , that it kept up the required heating effect by an intermittent current , and therefore by the passage of a much less quantity of electricity than would be required to produce the same heating effect if flowing in a nearly constant current ( the rate of generation of heat being proportional to the square of the strength of the current at each instant , while the looked-for convective effect is proportional simply to the strength of the current at each instant , and is therefore , on the whole , proportional to the whole quantity of electricity that passes ) . In order , therefore , that the current might be kept as nearly as possible constant at the particular strength required to maintain the heating effect used , I had the following regulator constructed . 71 . Two iron tubes , AB , CD , 20 inches long and f ths of an inch in diameter , open at the top but closed at the bottom , are bound firmly together with insulating blocks of wood , AC and BD , so as to be parallel to one another . Pieces of thin sheet copper are bent into cylinders ; to their tops pieces of thick copper , E , E , are soldered , and the copper cylinders are put into the iron tubes . To each end of a piece of thick copper wire , shown separately at F , two pieces of No. 18 iron wire are fixed , one of the same length as the iron tubes , and the other less than half that length , and the two branches are parallel , and at such a distance that when their ends are introduced into the two tubes , they move along their axes . To use the regulator , the tubes are filled with mercury , the apparatus is put into the circuit by connecting with EE , and the requisite amount of resistance is introduced by raising G , which is kept in any position by having one end of a cord fixed to its upper part , carried over a pulley , and stretched by a counterpoise hung at its other end . [ Great improvement has been since made in the regulator , by using , instead of No. 18 iron wire , thick copper wire tapering to points at the lower ends ; and by attaching cups of gutta percha to the tops of the iron tubes allowed to communicate with the interior by small holes , to serve as overflow cisterns for the mercury . By this arrangement the tubes were kept always full of mercury , and irregular contacts between the connecting conductor and the interior of empty parts of the tubes were prevented . Nov. 1856 . ] 72 . The apparatus was set up as shown in the accompanying view . The battery connexions were completed with the regulating break partly up , so as to check the current somewhat , and prevent injury from sudden overheating in any part of the conductor . All properties , then , of electric and thermal conductivity , of magnetic inductive capacity and retentiveness , and of thermo-electric rank and its variations from one temperature to another , may be characterized as electro-dynamic ; and the degrees to which these properties are possessed by different substances may be called their electro-dynamic qualities . Again , the variation which absolute magnetic inductive capacity , and magnecrystallic axial differences , experience with change of temperature may obviously be made the means of a transformation of heat into common mechanical energy , and we have thus a set of magneto-dynamic properties of matter which may almost in the present state of science be regarded as intrinsically electric , but which at all events ( when we consider that the motions contemplated , taking place as they do under magnetic force , cannot but be accompanied by electric currents ) may be fairly classed under the general designation of electro-dynamic . The variations of intrinsic magnetism , of magnetic inductive capacity , and of magnecrystallic properties , produced by variations of temperature , are therefore included among the electro-dynamic qualities of metals which I propose to investigate , although I have as yet made no progress in this branch of the subject . PART I. ON THE ELECTRIC CONVECTION OF HEAT , SS 4 to 77 . ^S 4 to 18 . Theoretical Indications . SS 4 to 9 . Origin of the Investigation . 4 . In first attempting an application of the principles of the Dynamical Theory of Heat to show the mechanical relation between cause and effect in thermo-electric currents , I supposed the effects thermal and mechanical that can be produced by a thermo-electric current in any part of its circuit to be , as first suggested by Joule , due to the heat absorbed , according to Peltier 's discovery , at the hot junction in virtue of the current crossing it , and I pointed out that the current crossing the cold junction must evolve a quantity of heat which , were this supposition true , would be less than that absorbed at the hot junction , by an amount precisely equivalent to all the effects , produced by the current in the rest of the circuit* . 5 . Introducing Carnot 's principle , as modified in the Dynamical Theory of another is electricity set into a state of motion ; that this electric motion subsides wholly into heat in most cases , either close to its origin and instantaneously , as when the solids are both of metal , or at sensible distances from the actual locality of friction and during appreciable intervals of time , as when the substance of one or both the bodies is of low conducting power for electricity ; and that it only fails to produce the full equivalent in heat for the work spent in overcoming the friction , when the electric currents are partially diverted from closed circuits in the two bodies and in the space between them , and are conducted away to produce other effects in other localities . Still , no hypothesis need be implied by using the expression " the frictional generation of heat by an electric current , " as defined in the passage quoted , and it is introduced into the present paper with no other justification than its convenience . After a few minutes the break was raised further so as to reduce the current very much , and the liquid began to rise in the stem of each of the glass tubes , showing that both air-thermometers at first acted perfectly . One of the thermometers was then steadied with great ease to a small fraction of a scale-division by using the regulator . The liquid in the other thermometer was observed , and its position occasionally noted . The direction of the current was reversed every few minutes , as before , by means of the ordinary commutator . Fig. 11 . 73 . Slight differences were observed in the free thermometer after the reversals , but as yet no very decisive indications of the looked-for effect appeared . The mercurial thermometer beside the central conductor indicated less than 80 ' Fahr. ( 27 ' Cent. ) , its column of mercury having not yet become visible , after the experiment had been continued in this way for several reversals . 74 . The regulating break was then pushed down until a somewhat further elevation in the temperature of the platinum was indicated by a considerable escape of air in bubbles from the open ends of the thermometer-tube . The break was again drawn up until the liquids again mounted in the stems . One of the thermometers was again steadied by the regulator , and , the other being observed , the experiment was continued as before . A decided effect now appeared almost immediately after each reversal . The free thermometer regularly indicated a higher temperature when the current nominally entered by the end next it , and a lower temperature when the current nominally entered by the remote end . After four reversals this part of the experiment had lasted about twenty minutes , and the mercury thermometer beside its middle showed 104 ' Fahr. ( 40 ' Cent. ) . 75 . The break was again pushed down for some time , and again raised till the liquid rose in each thermometer-tube , and the experiment was continued as before for four reversals , the central mercury thermometer rising to about 150 ' Fahr. ( 66 ' Cent. ) . The free thermometer rose and fell alternately through several scale-divisions almost immediately after each reversal , and showed the same con vective effect as had previously been observed by smaller indications . 76 . The bridge was again pushed down and air again escaped copiously from the thermometers , but very soon beads of liquid began to appear following one another rapidly down the capillary tubes from the interior of the conductor . As the spirits of wine had not once been allowed to run up into the bulb of either thermometer , these beads of liquid could be nothing but products of the distillation of the oil which had been used in the luting of the central plug ; and on taking away the cups of spirits of wine from below the tubes , the smell and taste of the small quantities of liquid which continued to descend gave unmistakeable evidence of their origin . After this it was scarcely possible to get any satisfactory indication from either of the air-thermometers ; but the experiment was continued , and one or other of them , when by any means the beads of disturbing liquid could be sufficiently got rid of for a time , was steadied to a constant temperature ; the other thermometer being observed when possible , and the reversals repeated as before . The same result was still obtained ; and on the whole , notwithstanding the defect which caused so much inconvenience , it was very decidedly established by the experiment that the Resinous Electricity carries heat with it in platinum . 77[Added Dec. 1856 . ] After many unsuccessful trials on short brass tubes , first with air-thermometers of the metal itself and capillary glass tubes arranged as in the platinum tube ( S 69 ) , and latterly with glass air-thermometers ( S 62 ) having very small cylindrical bulbs , the following conclusive experiment was made a few days ago . Four of the large double cells , connected to form a single Daniell 's element , exposing 10 square feet of zinc to 17 square feet of copper , were used to send a current through a piece of brass telescope tube 6 inches long , \#163 ; of an inch diameter , and ground as thin as it could be without breaking it up by emery-paper , over the length of 3^ inches which was left between the near sides of gutta-percha coolers , fitted to it in the manner represented above ( see fig. 11 , S 72 ) . Streams of water being , as in other experiments , kept running through the coolers , and the regulating break ( S 71 ) being used to keep the liquids within range in the tubes of the airthermometers , a small mercurial thermometer pressed against the middle of the brass tube , with its stem and scale projecting out through the cotton wool , indicated from 190 ' to 195 ' Fahr. ( 90'-6 Cent. ) . The regulator was not used so much as it might have been with advantage ; but , notwithstanding great unsteadiness in the indications of the two air-thermometers , the observations showed decidedly , after each reversal of the current , a cooling effect on the thermometer next the entering stream , in every case in which the irregularities were not so great as to make a comparison impossible . This effect is manifest from the following four cases , selected merely as being those in which one of the thermometers was most nearly steady during a few minutes of flow of the current , first in one direction and then in the other . Current entering Readings , in arbitrary scale-divisions , of by end next Thermometer A. Thermometer B. 2 IA 43 bl ' IB 42 44\#163 ; n JA 41 41 IB 41 34\#163 ; m IA 31i 26i IB 29\#163 ; 16i IV iA 27I 22 'IB 20i 121 Hence the conclusion ( see below , SS 102 and 103 ) , that the Vitreous Electricity carries heat with it in brass , which I anticipated three years ago from the-mechanical theory * , is now established by a direct experimental demonstration . PART II . ON THERMO-ELECTRIC INVERSIONS . 78 . Cumming 's discovery of thermo-electric inversions having afforded the special foundation of that part of the theory by which I ascertained the general fact of electric convection in metals , and every observation of a thermo-electric inversion being a perfect test as to the relative positions of the two metals between which it is observed in the Table of Convections ( see below , S 103 ) , I was induced to make experiments with a view to finding new instances of inversion , and to determine in each case , with some degree of precision , the temperature at which the two metals are thermoelectrically neutral to one another , 79 . In the experiments on thermo-electric inversion described by Cumming , and by Becquerel , the only other experimenter , so far as I am aware , who has published observations on the subject , one junction between the two metals is generally kept cool , while the other is raised until the current indicated by the galvanometer , instead of going on increasing , begins to diminish , comes to a stop , and then sets in the reverse direction^ . 80 . In this way Cumming found that " if gold , silver , copper , brass , or zinc wires be heated in connexion with iron , the deviation [ indicating the current ] , which is at first positive , becomes negative at a red heat J. " Many other experimenters have professed themselves unable to verify these extraordinary results , and have attempted to explain them away by attributing them to coatings of oxide formed on the metals , or to other causes supposed with equally little reason to exercise sensible disturbing influences ; but the descriptions , given by the original observers , of their experiments leave no room for such doubts . It is certainly not easy to get the inversion between copper and iron ( with such specimens as I have tried ) by the heat of a spirit-lamp , applied as described by Becquerel to one junction while the other is left cool ; but I readily obtained it by raising the other junction somewhat in temperature , with the first still kept at a red heat . Probably if the atmospheric temperature had b^en higher , or if a somewhat more intense red heat had been obtained from the spiritlamp , I should at once have obtained the result simply in the manner described by the previous observers . 81 . The easiest way to verify the thermo-electric inversion of iron and copper is to take a piece of iron wire a foot or two long , and twist firmly round its ends two copper wires connected with the electrodes of any ordinary astatic needle-galvanometer . Then first heat one of the junctions with the hand , or by holding it at some height over a flame ; and note the deflection , which will be found such as to indicate a current from copper to iron through the hot junction . Again , heat both junctions in flame , or in sand at any temperature above 300 ' Cent. , and withdraw one a little from the hottest place , so that while both junctions are at temperatures above 300 ' Cent. , that which was heated in the first experiment maybe still decidedly hotter than the other . The deflection will now be found to be the reverse of what it was before , and will be such as to indicate a current from iron to copper through hot . The reversal of the current may be very strikingly exhibited by allowing the two junctions gradually to cool , while ensuring that the same one remains always somewhat above the other in temperature . When the mean of the temperatures of the two junctions falls below 280 ' Cent , or thereabouts , the primitive deflection will be again observed . All these phenomena are observed indifferently whether the copper wires be simply twisted on the ends of the iron wire , or brazed to them , or tied to them by thin platinum or iron wire . 82 . Similar phenomena may be observed without the necessity of going to so high temperatures , by soldering galvanometer electrodes of copper to the ends of a double platinum and iron wire , and treating this compound circuit in the manner just described , only with a more moderate application of heat . If the platinum wire be very thin in comparison with the iron one connected along with it , the circumstances will be but little altered from those observed when iron simply is used . By taking a thicker platinum wire , or several thin ones together , in connexion with the same iron wire , or by using a thinner iron wire and the same platinum , the neutralization and reversal may be shown with temperatures below the boiling-point . Most specimens of platinum wire thus applied reduce the neutral point of copper and the compound platinum and iron wire much below the temperature of melting ice , when the proportion of platinum to iron in the bundle is sufficiently increased ( the limit , of course , being the neutral point of copper to the platinum itself . See below , SS 83 , 84 ) . 83 . A certain specimen of platinum wire in my possession , when tested by such elevations of temperature as could be produced by the hand , was found to lie in the thermo-electric series , on the other side of copper from the position in which platinum is placed in all statements of the thermo-electric qualities of metals previously published . That is to say , when connected by copper electrodes with the circuit of a galvanometer , and when heated at one junction up to ten or twenty degrees above the atmospheric temperature , a current set from copper to platinum through hot . On raising the temperature of the hot junction towards the boiling-point of water , the strength of the current began to diminish ; came to a stop when a temperature I suppose little above that of boiling water was reached ; and set in the reverse direction with increasing strength when the temperature of the hot junction was further raised , the other junction being kept all the time at the atmospheric temperature . I afterwards found that this specimen of platinum wire ( referred to under the designation Pj in what follows ) became neutral to ordinary copper wire at the temperature 64 ' Cent. 84 . Of two other specimens of platinum wire which I tried with copper , one ( marked P2 ) gave indications of a neutral point about the zero of Fahrenheit 's scale , but the other ( P3 ) remained , for the lowest temperatures I reached , always on the same side of copper as that on which platinum appears , at ordinary and at high temperatures , generally to lie . When these three platinum wires were tried with one another thermo-electrically , they gave , as was to be expected , the mutual thermo-electric indications of different metals lying in the order Bismuth , P3 , P25 P\#8222 ; Iron , Antimony . They retained all the same qualities after being heated to redness ; and in a great many experiments performed upon them , in which I have found them extremely convenient as thermo-electric standards , have exhibited perfect constancy in their thermo-electric bearings . I have not yet discovered on what their differences depend , but in all probability it is on the degrees to which they are alloyed with other metals . 85 . The fact of copper changing in the thermo-electric series from below the position of the platinum specimen P2 to above that of iron , when the temperature is raised from -30 ' or -20 ' Cent , to 300 ' , proves that every metal which lies between P2 and iron for any intermediate temperature , must become neutral to either P2 or copper , or iron at some temperature between these limits . Now nearly all the common metals , for instance , lead , tin , brass , zinc , silver , cadmium , gold , lie between platinum and iron in the thermo-electric series at ordinary temperatures , and no doubt many of the rarer metals ( I have found aluminium to lie between P3 and P2 ) are to be ranked within the same limits . Hence at temperatures easily reached and tested , neutral points may be looked for with the certainty of finding them , between each of those metals and one or other , if not several , of the metals and metallic specimens ( P2 , Pi9 Copper , Iron ) referred to above . Taking then the platinum specimens Pw P2 , P3 as standards , and using besides ordinary copper and iron wires , I commenced investigating their thermo-electric relations to as many other metals as I could obtain . 86 . In experiments to determine temperatures of neutrality , the first apparatus which I employed for regulating the temperatures of the two junctions , consisted of copper vessels placed side by side in which oil could be raised by gas-burners as high in temperature as the mercurial thermometer can be used , that is to 340 ' or 350 ' Cent. , or somewhat above the boiling-point of mercury . To do away with irregularities from the flame and cold air playing unequally on the sides of these vessels , smaller ones were placed on wire stands within them , and were completely filled and surrounded with oil . In each experiment a wire or slip , about 18 inches long , of one of the metals to be tested , had somewhat longer wires or slips of the other soldered to its ends . The compound conductor thus constituted was bent into such a shape that the two junctions of the metals could be placed near the centres of the oil-baths ; it was supported in this position , carefully insulated from touching the Fig. 13 . copper vessels and from all other metallic contacts ; and thermometers were put with their bulbs in the oil as close to the junctions as possible . The gas-furnaces were applied below and round the sides of the large copper vessels , so that they could be regulated to any desired temperatures . 87 . After this apparatus had been used in several experiments , and neutral points between copper and iron , copper and Pw lead wires and Pw and brass and Pl had been determined , I saw reason to alter the arrangements in various respects , and had another apparatus constructed , according to the following description . 88 . Two small oil-baths were made , each of an outside partly cylindrical and partly plane sheet of copper , and a concentric copper tube 5 inches long and - & ths of 4z 2 Fig. 15 . Fig. 16 . 702 PROFESSOR THOMSON ON THE ELECTRO-DYNAMIC QUALITIES OF METALS . an inch diameter brazed to it by ends of sheet copper , shaped as shown in the diagram . The space round the inner tube and within the outer sheet and ends was filled with oil completely covering the inner tube , and , when heated , rising into the space between the upper parallel plane parts of the outer sheet . A narrow ring of sheet metal with a long slip projecting from one side for holding it by , was put in the inner tube before the other parts were brazed on , and during an experiment was kept as constantly moving from one end of the bath to the other and back as was required to keep the whole mass of oil at one temperature . The second drawing represents , on the actual scale , a section of either bath through the position occupied by its stirrer . This diagram also shows a section of an external case of sheet metal which supports the bath , and serves as a flue to carry the flame and products of combustion round its sides . The rows of gasburners for the two baths were fixed in a line , and each burner regulated by a separate stopcock . The outer cases are screwed to the same stand , and the copper vessels holding the oil are pushed into them and rest with their axes in a line over the burners . The ends of the T)aths and of the outer cases are kept about one-fourth of an inch apart , and their supports are also made quite separate , which was found to be necessary to allow one of the baths to be kept cool , while the other is raised to a high temperature . ( In the third drawing , the stems by which the stirrers are held are accidentally omitted . ) 89 . When the baths and their furnaces are all fixed in their proper positions , a tube of thin glass , about 10^ inches long , just small enough to enter easily , is pushed into the inner tubes of the baths , and is left resting there , with its ends projecting a little outside their remote ends . In recent experiments I have substituted a simple roll of paper for the glass tube , and have found it answer quite as well . 90 . A compound conductor , to be tested thermo-electrically in this apparatus , conFig . 14 . sists of a wire or a thin bar of one metal , or a bundle of wires of two different metals 5J inches long , with wires of from 18 to 30 inches long of another metal soldered to its ends . To avoid circumlocution I shall call the former the mean conductor , and the wires soldered to it the electrodes , of the thermo-electric arrangement . The connexions between the mean and the electrodes are generally made by brazing , or by hard silver solder , when temperatures much above the boiling-point of water are to be used . 91 . A conductor thus prepared of two metals to be tested is drawn through the glass tube till the mean occupies a position , lying on the glass or paper 'tube , with its centre under the centre of the tube , and consequently with its ends about the middle of the hollow spaces surrounded by the oil-baths . 92 . The electrodes are carried from the ends of the insulating tube to the connexions required for completing the circuit through the coil of a galvanometer . These must essentially be maintained at the same temperature , unless the electrodes of the thermo-electric arrangement be copper , the same as those of the galvanometer . After trying several obvious , more or less troublesome plans to secure the fulfilment of this condition , I found a perfectly effective way simply to the the connexions firmly together as close to one another as possible , only separated from contact by a fold or two of paper wrapped round each , and to the a quantity of paper , or to make up a bundle of cotton wool , or some other bad conductor , round the two , for two or three inches on each side of the junctions . The junctions themselves , except when they are between homogeneous metals , are not made by binding-screws , but either by soldering , or by cleaning the surfaces and then tying the metal firmly together by fine twine . To avoid mistakes and prevent the necessity of disturbing the bundle round the junctions , in tracing the courses of the conductor on the two sides of it , a thread or mark of some kind is attached to one galvanometer electrode , and a corresponding mark on the electrode of the thermo-electric apparatus to which it is joined . This system of electric insulation and thermal connexion between junctions of dissimilar metals , I have found very convenient in a great variety of thermo-electric and other electro-dynamic experiments , and when it was used I have never observed the slightest trace of a current attributable to any difference of temperatures in the parts of the circuit to which it is applied . 93 . The conductor being thus arranged , two thermometers are pushed into the glass or paper tube from its ends and placed with the centres of their bulbs as close as possible to the metallic junctions , and with their graduated tubes extending nearly horizontally outside the apparatus , but inclined upwards as much as the inner diameter of the insulating tube and their dimensions permit , so as to check as much as possible the tendency ( in some of the thermometers found very inconvenient ) of the column of mercury to divide when sinking rapidly . All the space inside the glass or paper tube left vacant by the thermometers and the conductor is filled with cotton wool , well pressed in to prevent currents of air . 94 . This apparatus has many advantages over that first used and described in above : the temperatures of the baths can be changed with great rapidity , in consequence of the smallness of the quantities of oil which they contain ; and by watching the thermometers and adjusting the gas-burners , can be regulated as desired with great ease . I have found it not a small practical advantage to be freed from the necessity of bending the mean part of the conductor to be tested , and of making the arrangements to prevent irregular contacts and to keep the junctions and the thermometers in their proper positions immersed in the oil . When a rare metal is to be tested , or one , such as sodium or potassium , which cannot be kept in air , it will be of great consequence to be able to apply the tests to a little straight bar or slip only a few inches long , or to a small column filling a glass tube . 95 . For experimenting at low temperatures a modified apparatus was made , consisting of a double wooden box , each compartment , nearly a cube of 4 inches side , fixed to a common base with a space of about J inch between their sides , and a glass tube running through them and cemented at the apertures in the sides so as to hold water-tight and resist the action of acids which might be employed in freezing mixtures . The conductor to be tested and the thermometers are arranged in this glass tube , as in that of the other apparatus ( S 89 to 93 ) ; and while a freezing mixture is kept in one compartment , the other is either allowed to take the atmospheric temperature , or is heated by hot water or steam . 96 . The way of experimenting which I followed , was to raise the temperature of one bath until a deflection of the galvanometer-needle became sensible ; then to go on raising it , and letting that of the other follow , so that the two thermometers may indicate as nearly as may be a constant difference of temperatures ; and to watch the needle until a reversal is observed , or until the limit of temperature which the arrangement admits of is reached . As soon as a reversal is obtained , the two thermometers are allowed to sink until the needle begins to return from its reverse deflection . When it approaches zero the thermometers are kept from any rapid changes , but allowed to sink very slowly , with always the same difference , or at least with a quite decided difference of the same kind as that raised between them at the beginning . The last readings of the sinking thermometers which give a sensible deflection before the original deflection is recovered , several readings when the needle appears perfectly at zero , and the first readings when the needle is discovered to deviate again in the original direction , are carefully noted . The arithmetical mean of the temperatures of the two thermometers for each of these simultaneous or nearly simultaneous readings is taken ; and it is generally found that the means derived from the readings taken when no deflection can be discerned , lie within a fraction of a degree of the mean of the last sinking mean temperature of the junctions which show one deviation , and the first which shows the deviation in the other direction . The mean of either the readings which Fig. 17 . give no deviation , or of the last and first which give the contrary deviations , or of all these readings together , according to the nature of the memoranda made by the observer , is taken as a determination of the neutral point of the two metals , that is , the temperature at which they are thermo-electrically like one metal , or thermoelectrically neutral to one another . In the course of one experiment several such determinations , both with descending and with ascending mean temperature , are made , and if possible also , with first one and then the other junction higher . 97 . Either in one experiment , or with the same apparatus on successive days , determinations are sometimes made with as considerable a variety of differences of temperature between the two junctions as is attainable . Sometimes the difference of temperatures used is so small as to give very slight indications of electro-motive force , even when the mean of the temperatures of the junctions differs widely from the neutral . point , in which cases , of course , the test is deficient in sensibility . The best determinations are generally those derived from observations showing the galvanometer at zero , with the widest difference between the temperatures of the junctions , to which the thermometers are applicable with trustworthy indications ; as , for instance , 100 ' or 150 ' Cent. , which are attainable in the most favourable cases , being those in which the neutral point is at about midway between the temperatures of freezing and boiling water . The differences between these determinations sometimes amount to a degree or two , and even to several degrees when zinc was one of the metals ; but generally the final mean for the neutral point does not differ by more than a degree from any single determination considered as satisfactory at the time it was made . 98 . The mutual interchanges of thermo-electric order observed in various specimens of zinc , gold and silver , occasioned considerable perplexity , which has only been cleared up by observations made subsequently to the communication of this paper . The following determinations were made at different times and by different observers , as noted : Observer . Date . Metals . Neutral points . Mr. C.A.Smith Sept. 27 , 1854 ^S^^'ZZZZZ ~ *06 Mr. C.A.Smith Aug. 18 , 1854 ^^^d^ZZZZZ ~ 1 > B Mr-c-A.smith sept , s , 1854 z^Xirodes " : : : : : : : : : : : : : : : + 8 > 2 MrCASmith *I* 2 ' . 1854 IfnTsp'dln^iyeiectVod'e ; 43'9 Mr. G. Chapman and 1 Jan " T on 1QKss i and , Feb'\#8222 ; , 5_ Silver electrodes 51 -,.\#187 ; 5 Mr. J. Chapman Cranston ... ) Jan " T 29 > on 1QKss i 856 > and , \#8222 ; Feb ' , 5_ Zinc specimen ( 2 ) mean ... 51 -,.\#187 ; 5 Mr. G. Chapman and 1\#8222 ; Feb,.\#8222 ; , , , 1856 Silver mean Afi.ss 4t > 5O Mr. J. Cranston ... / \#8222 ; Feb,.\#8222 ; , , , 1856 Zinc ( 1 ) electrodes 4t > Afi.ss 5O Mr. G. Chapman and I , - , , Feb , o.c 1856 Silver mean o8 ie.ie 18 Mr. J. Cranston ... / , - , , Feb , o.c 1856 Zinc ( 2 ) electrodes o8 ie.ie 18 Mr-J-M-y A^1856 STdSKto " : : : : : : : : : : : : : : : 66-95 Mr. G. Chapman and " 1 v teD , 18O ' , e~ Gold mean 71 Mr. J. Cranston ... / teDv , 18O ' e Zinc electrodes Mr. G. Chapman and I p , lo.c Gold mean fiQ.7fi b9 7 ' Mr. J. Cranston ... / Feb-1856 p , lo.c Zinc electrodes mean b9 fiQ.7fi 7 ' IArd}^^\#171 ; 6 GImr^r ... : : : : : : : : : : : : } 7'-8 M'-j-M-y Aug.2i.i856 Giesdes-:::::::::::::::}-^ Heat* , I found a relation between the quantities of heat absorbed or evolved by currents crossing metallic junctions at different temperatures ; which led immediately to a general expression for the electrical condition of a circuit of two metals with their junctions kept at any stated temperatures . 6 . From this it appeared that the electro-motive force should follow the same law of variation in every case , being expressed by a constant , ( representing the thermoelectric difference between the two metals , ) multiplied into an absolute function of the temperatures of their junctions , namely , the difference of their temperature on the absolute thermometric scale since proposed by Mr. Joule and myself , and demonstrated by our experiments-^ to agree very approximately with their difference of temperature as indicated by an air-thermometer . Finding this conclusion contradictory to the statements made by experimenters , that the electro-motive force does not vary with the temperature of the junctions according to the same law in circuits composed of different metals , I perceived that Peltier 's discovery did not afford a sufficient explanation of the source whence a thermo-electric current derives its energy , but that electric currents must possess the previously undiscovered property of producing different thermal effects in passing from cold to hot and from hot to cold in the same metal , and must possess this property to different amounts in different metals . 7 . Taking this new property of electric currents into account along with that discovered by Peltier , and introducing an application of Carnot 's principle , I arrived at expressions for the relations between the heat absorbed and evolved in various parts of a circuit of any different metals , and between the electro-motive force and the temperatures of the junctions , which appear to be in complete accordance with the facts . These investigations were communicated in December 1851 , to the Royal Society of Edinburgh^ . 8 . Still simpler theoretical considerations ( SS 10 to 18 below ) regarding the source of energy drawn upon in a thermo-electric current , make it certain that the phenomena of inversion discovered by Cumming could not exist , unless the metals presenting them had the property of experiencing , when unequally heated , unequal thermal effects from electric currents passing through them from hot to cold , and from cold to hot . Having satisfied myself , both by an examination of the evidence afforded by Becquerel 's experiments ( the original investigation on the subject by Cumming being at that time unknown to me ) , and by actual observation , in experiments of my own S , Of the two results for the neutral point between silver and gold , only the last can be reconciled with the indications derived from the previous results as to the relative positions of these and the other metals tried along with them ; and accordingly 5O#7 has been taken as the neutral point of gold and silver in the thermo-electric diagram given below ( S 101 ) . The first result , 70'*8 , was found as the mean of several determinations , from none of which it differed by more than 0'7 , and the discrepance can scarcely be attributed to errors of observation , but is probably due to slight differences in the specimens of gold and silver used in the different experiments . That very slight chemical differences in specimens of gold and silver wire may make great alterations in the temperature at which they become thermo-electrically neutral to one another , is readily understood by glancing at the diagram given below ( S 101 ) , and observing how close together the lines for gold and silver lie . 99 . The question , Does the difference between the specific heat of electricity in two metals vary with the temperature* ? may be answered by experiments showing the law according to which the means of widely different temperatures of the junctions giving no electro-motive force deviate from the true neutral point , which is the mean of any infinitely small difference of temperature giving no electro-motive force . I have not yet obtained indications of such a deviation in any case , having been prevented from prosecuting the inquiry by delays in the construction of a suitable air-thermometer . The examination I have been able to give the subject is only sufficient to show that the arithmetical mean of the temperatures of the two junctions giving no current , is probably in general within a degree of the true neutral point , when the difference between those temperatures does not exceed 100 ' Cent. The following summary of a series of experiments made on two consecutive days may serve as an example of the degree of consistence of the results obtained by the method which has been explained , in a case in which the two metals deviate rapidly from one another above and below their neutral point . Sheet-lead Electrodes ; Vx mean . Determinations by Mr. C. A. Smith , May 17 & 18 , 1854 . Difference Half sum of mercurial thermometer temperatures of temperatures . giving no current . m 12I . " 7\#161 ; i yi2 'l'i U14 Mean yi2 U14 121'.* ; 1\#191 ; 1 5 7li mJ 121'.* ; 1\#191 ; 1 5 70 122 185\#163 ; 120jf USi m* Mean H3 121* JJeaD Mean iAi 133 Uli iAi 4 125\#163 ; 12 ' ' 68\#163 ; 122 Mean 50 123 l22'-5 Mean of temperatures by mercurial thermometer giving no current . Differences from 50 ' to 77 ' 122'-15 Differences from 125 ' to 185 ' ... 121'-4 * See " Dynamical Theory of Heat/ 1 S 115 , equations ( 15 ) and ( 17 ) . These results seem on the whole to show that the mean of apparent temperatures giving no current is rather less for the wide than for the narrow ranges , in the case of the two metals concerned ; that is , that the mean of the apparent temperatures giving no current is somewhat below the true neutral point . I need scarcely remark , however , that even if this indication could be relied on , it would be necessary to compare the actual mercurial thermometers which were used , with an air-thermoineter , before any conclusions of value could be drawn from it regarding the constancy of the difference of specific heats of electricity in lead and platinum . 100 . The following Table shows the results of observations leading to actual determinations of neutral points between various pairs of metals : -14 ' C. -12'-2. . -5'7 . -3'-06 . -l'-5 . 8'-2 . 33 ' . 36 ' . 38 ' . 44 ' . I 44 ' . 47 ' ... 71 ' . P3 Pi Silver . Pj Pj Px Tin . P2 P2 P2 Lead . Different specimens of Silver . Brass . Cadmium . Gold . Gold . Silver . Zinc . Brass . Lead . Brass . Tin . Brass . Different specimens of Zinc . Some tempera53 ' . 57'* . 64 ' . 71 ' . 99 ' . 121 ' . 130 ' . 162'-5 . ture between 237 ' . 280 ' . 223 ' & 253'-5 . P2 Hard steel . F1 Gold . Pj Px F1 Iron . Iron . Iron . Iron . Double wire of " 1 Palladium 11*31 grs.w Cadmium . Copper . Zinc . Brass . Lead . Tin . Cadmium . Gold . Silver . Copper , and Copper 19*41 grs. J The number at the head of each column expresses the temperature Centigrade by mercurial thermometers , at which the two metals written below it are thermo-electrically neutral to one another ; and the lower metal in each column is that which passes the other from bismuth towards antimony as the temperature rises . It was also found that Aluminium must be neutral to either P3 or Brass , or P2 , at some temperature between 14 ' C. and 38 ' C ; that Brass becomes neutral to Copper at some high temperature , probably between 800 ' and 1400 ' ; Copper to Silver , a little below the melting-point of silver ; Nickel to Palladium , at some high temperature , perhaps about a low red heat ; and P3 to impure mercury ( that had been used for amalgamating zinc plates ) , at a temperature between -10 ' and 0 ' . P3 appears to become neutral to pure mercury at some temperature below -25 ' Cent. 101 . The following Diagram exhibits graphically the relative thermo-electric bearings of the different metals , and may in fact be regarded as a series of tables of the thermo-electric order of metals at different temperatures from -30 ' to 300 ' Cent. in Part I. , that the vitreous electricity carries heat with it in copper ( ^ 54 ) , or , as it may be expressed , the electric convection of heat is positive in copper . From the diagram we infer that it is greater , and consequently positive , in Brass . That it is positive in brass has been proved also by direct experiment ( SS 67 and 77 ) . We infer also with certainty from the diagram , that the electric convection of heat ( whether positive or negative ) is greater in Zinc than in Gold , and greater in Gold than in Silver ; that it is greater in Brass , Tin , Lead , Copper , Zinc , Gold , Silver , and Cadmium than in Platinum ; that it is greater in Brass , Copper , Gold , Silver , and Cadmium than in Iron ; that it is greater ( that is to say , since it has been proved , S 76 , to be negative , less negative ) in Platinum than in Mercury ; and that it is greater in Nickel than in Palladium . In Cadmium , as we may judge by the eye from the diagram , the convection is probably greater than in Copper ; and in Palladium probably less ( that is , greater negatively ) than in Platinum . 103 . These conclusions , certain and probable , are collected in the following Table of Convections , in which the different metals are arranged in order of the amounts of the electric convection of heat which they experience , or in the order of the values of " the specific heat of electricity in them . " Electrical Convection of Heat In Cadmium Positive , Brass Positive . Copper Positive . Order doubtful A Lead.1 ^. . T. > equal Positive . ^. . Zinc Positive , Zero , or Negative . Gold Positive , Zero , or Negative . Silver Positive , Zero , or Negative . Iron Negative . Order doubtful . Platinum Negative . Nickel Probably Negative . Probably nearly r Palladium Probably Negative . equal . 1 Mercury Negative . PART III . EFFECTS OF MECHANICAL STRAIN AND OF MAGNETIZATION ON THE THERMO-ELECTRIC QUALITIES OF METALS . 104 . Physical agencies having directional attributes and depending ( as all physical agencies we know of except gravitation appear to do ) on particular qualities of the substance occupying the space across or in which they are exerted , are transmitted or permitted with different degrees of facility in different directions if the substance is crystalline . The phenomenon of crystallization , exhibiting different chemical 5 a2 affinities on different bounding planes , between a growing crystal and the fluid from which it is being formed , and the cleavage properties ( different specific capacities for resisting stress in different directions ) afford the primary illustrations of this statement . It is probable that the proposition asserted is a universal proposition in the sense , that there is no kind of physical agency falling under the category referred to , which does not meet with different capacities for receiving it in different directions in some crystals . There certainly may be , and probably are , crystals which transmit certain physical agencies equally in all directions . Crystals of the cubical system , for instance ( unless possessing the conceivable dipolar rotatory property * , from which some , if not all , are certainly exempt ) , conduct heat and electricity equally in all directions , and have equal magnetic inductive capacities and equal thermo-electric powers . But thermal and electric conductivity , magnetic inductive capacity , and " thermo-electric power-f~ " are undoubtedly different in different directions in many , if not in all , crystals not of the cubical system . Many crystals have not shown any marked difference in their absorption of light according to the direction of its propagation through them ; but some undoubtedly do show a difference of this kind , to such a degree as to give sensibly different colour to light passing short distances through them in different directions^ . Faraday had good reason , after making the discovery of the induction of electro-polarization in non-conducting substances^ , to try the specific directional qualities of crystals used as dielectrics ; and although he found no sensible differences in the inductive capacities of the crystals ( rock crystals and Iceland spar ) which he tried for this kind of action , in different directions , it appears highly probable that induced electro-polarization will sooner or later be ascertained to be no exception to the general rule . 105 . Another very general principle is , that any directional agency applied to a substance may give it different capacities in different directions for all others . Whether or not this is true as a universal proposition , events have proved that the probability of its being true in any particular case is quite sufficient to warrant an experimental inquiry . Brewster discovered that mechanical stress induces in glass directional properties with reference to polarized light , which are lost as soon as the stress originating them is removed . These properties were shown by Fresnel to be of the same kind as the property of double refraction possessed by a natural crystal . Experiments made by Sir David Brewster and Mr. Clerk Maxwell prove that isinglass and other gelatinous substances dried under stress , thin sheet gutta-percha permanently strained by traction , and probably all non-brittle ( or plastic ) transparent solids when permanently strained otherwise than by uniform condensation or dilatation in all directions , possess double refraction as a property of the molecular alteration which they acquire under the stress and retain after the stress is removed . Again , magnetization , as Joule discovered , causes an elongation of iron in one direction ( that of the magnetization ) and a contraction in all directions perpendicular to it , with no sensible change of volume . Faraday discovered the wonderful dipolar optical property of transparent bodies in a magnetic field ( the first and only case known of any dipolar qualities , other than those of magnetic and electric reactive forces , called into existence by induction ) : Maggi discovered that magnetized iron conducts heat with a greater facility across than along the lines of magnetization * . 106 . In applying the dynamical theory of heat to thermo-electric currents in conducting crystals , I was led to consider the probable effects of mechanical strain , and of magnetization on the thermo-electric properties of non-crystalline metals , and in consequence entered on the investigation , of which the results , so far as I have yet advanced in it , are now laid before the Royal Society . 107 . To find the effect of longitudinal tension on the thermo-electric quality of a metal , I first took eight thin copper wires each capable of bearing about 10 lbs. , and y attaching their upper ends to a horizontal wooden arm at distances of about ' of an inch from one another , allowed them to hang down , each kept stretched by a weight of about\#163 ; Jb . They were connected with one another in order , and the first and last with the electrodes of a galvanometer , by nine wires soldered to them , as shown in the diagram ; the junctions between the successive wires being alternately in the upper and lower of two horizontal lines 4 inches apart . Every alternate wire was then stretched with a weight of about 3 lbs. , and a slip of hot plate glass was applied , sometimes to the upper and sometimes to the lower row of junctions . A deflection of the galvanometer needle was observed in one direction or the other , according as the glass heater was applied to one set of junctions or the other . The deflection was also reversed when the weights were changed to the alternate set of wires , and the heater kept applied to the same set of junctions . In every case the deflection was such as to indicate a current from stretched to unstretched through hot junctions . The uniform and consistent nature of the indications was such as could leave no doubt as to the result ; and I concluded that copper wire stretched by a longitudinal force bears to copper wire of the same substance unstretched , the same thermo-electric relation as that of bismuth to antimony . 108 . I next made a similar experiment on iron wire , varying the arrangement so that the weights could be rapidly shifted ; and again so that equal sets of forces could be applied to one or to the other of the two sets of wires , merely by pressing with the foot upon one or another of two levers . A perfectly decided result was at once obtained ; and I ascertained that the thermo-electric effect was induced and lost quite suddenly on the pressure being applied and removed . In this case the nature of the effect was the reverse of that found in the experiment on copper , the deflections being always such as to indicate a current in the iron wires from unstretched to stretched through the hot junctions . 109 . The thermo-electric effect which these experiments demonstrated to accompany temporary strain produced by a longitudinal force , was , in each of the metals , the reverse of that which Magnus * had previously discovered in the same metal hardened by the process of wire-drawing , and which I ascertained for myself to be produced in each case when the metal is hardened by simple longitudinal stress without any of the lateral action inseparable from the use of the draw plate . I thus arrived at the remarkable conclusion , that when a permanent elongation is left after the withdrawal of a longitudinal force which has been applied to an iron or copper wire , the residual thermo-electric effect is the reverse of the thermo-electric effect which is induced by the force , and which subsists as long as the force acts . 110 . I have made a single experiment demonstrating this conclusion for iron by means of a multiple tension apparatus , similar in principle to that described above ( S 105 ) . But with a somewhat more sensitive galvanometer than the one I used , the result may be shown in a perfectly decided manner ( for iron at least ) without any multiplication of the thermo-electric elements ; and a very striking experiment may be made on the following plan : A thin iron wire is wrapped three or four times round a wooden peg held firmly in a horizontal position , and again two or three times round another parallel peg , about 4 inches lower . A frame is rigidly connected to this second peg , so that it may remain stably in a horizontal position ; hanging from the wire and pulled down by the frame with either a light or a heavy weight attached to its lowest point . To keep the wire from slipping , the parts of it running from the pegs towards the ends are kept stretched by light weights tied to them ; and the slack parts below these weights are carried away to the Fig. 20 . galvanometer electrodes , with which they are connected in the manner described above ( S 92 ) . Any convenient source of heat is applied to the part of the wire bent round either peg , so as to keep it at some temperature , perhaps about as high as that of boiling water . If the wire be well annealed at the commencement of the experiment , and if weights be gradually added to the lower side of the frame , the galvanometer needle gradually moves to one side , indicating a current from the unstretched to the stretched round the hot peg ; and the deflection goes on increasing as long as weights are added , up to the breaking of the wire . If , however , before the wire breaks , the weights are gradually removed , the needle comes back towards its zeropoint , reaches zero , and remains there when a certain part of the weight is kept suspended . If this is removed the needle immediately goes to the other side of zero , and remains , indicating a current from the strained part into the unstrained part of the iron wire round the part wrapped on the hot peg ; that is , from strained to unstrained through hot , or as Magnus found , " from hard to soft through hot . " 111 . If weights be added again , as at first , this deflection is done away with , and the deflection that first appeared is regained , when the weight which previously allowed the needle to return to zero is exceeded . We thus conclude that iron wire hardened by longitudinal tension , may , by the application of a certain longitudinal force , have its thermo-electric quality reduced to that of unstrained soft iron , and by a greater force may be made to deviate in the other direction ; or that hardened iron under a heavy stress , of the kind by which it has been hardened , and hardened iron left free from stress , are on different sides of unstrained soft iron in the thermo-electric series . There can be no doubt but that the same property holds for copper wire , being in fact demonstrated by the experimental results described above in SS 107 and 109 . 112 . I have not yet investigated the thermo-electric effects of stress ( that is , the effects accompanying temporary strain ) in other metals than iron and copper ; but it appears probable that the same law of relation to the thermo-electric effects of permanent strain without stress will be found to hold in each case , since it has been established for two metals in which the absolute thermo-electric effects are of contrary kinds . I hope , however , before long to be able to adduce experimental evidence which will supersede conjectures on the subject . [ Since this paper was read I have verified the same law for platinum wire . ] 113 . The object which was proposed in entering on the investigation , being to test the thermo-electric properties of a strained metal , in different directions with reference to the direction of the strain , was not attained by comparing the thermo-electric properties of a longitudinally strained metal with those of the same metal in its natural state ; but it would certainly be promoted by discovering the effect of lateral pressure on a wire in modifying its longitudinal thermo-electric action . I therefore made the following experiments on the thermo-electric effects experienced during the application of a moderate lateral pressure , and of permanent strain after the cessation of excessive lateral pressure , in various wires . 114 . Experiment to discover the temporary effect of lateral pressure on the thermoelectric quality of iron wire : A rectangular bar of iron ( If inch square ) , with pieces of thin hard wood placed on two opposite sides , had fine iron wire laid in a coil of about twenty turns round it . The wood perfectly insulated the wire from the iron bar , and the different turns of the wire were kept from touching one another , by little notches cut in the edges of the pieces of wood . The whole coil was made firm , and its extreme turns tied down to the wood to prevent slipping . The ends of the wire , extending a foot or two on each side of the coil , were connected in the usual way ( S 92 ) with a galvanometer . The bar bearing the coil was laid with its two wooden faces horizontal , and one of them supported on a thin piece of hard wood lying on the stage of a Bramah 's press . Another thin piece of hard wood was laid upon the top of the coil , to prevent the upper part of it ( when , in the course of the experiment , it is forced upwards , ) from touching the roof of the press . Blocks of iron were placed on the ends of the bar , so that when the stage is pushed up they may be resisted by the roof , cause a heavy stress to act on the bar , and press the lower horizontal parts of the wire coil between the two pieces of hard wood touching them above and below . The same blocks are afterwards shifted to rest on the stage and bear the ends of the bar upon them , so that , when the stage is forced up , the upper parts of the wire coil may be pressed against the piece of hard wood above them , which will then be resisted by the roof of the press . Pieces of plate glass highly heated were applied to the vertical parts of the wire on one side of the bar , those on the other side being left cool , and the galvanometer was observed . Some slight deviation of the needle was generally noticed . Then the press was worked , and immediately a strong deflection took place , indicating a current in the iron coil , from the uncompressed portions through the heated vertical portions , into the compressed portions . The pressure was relieved , and the galvanometer needle returned nearly to zero . It was reapplied , and the same powerful deflection was observed . The glass heaters were shifted to the other side , and , the pressure being continued , the deflection of the needle became reversed . The pressure was removed , and by shifting the iron blocks , and working the press again , was applied on the other horizontal side of thecoil . The heating being kept unchanged , a reverse deflection was observed , powerful as at first . The current indicated was in every case from free irmi wire to pressed iron wire through hot , as is illustrated in the diagram , for a case in which the upper parts of the wire are compressed . 115 . From this , in conjunction with the result regarding the effect of longitudinal stress previously obtained , we may nearly conclude that a longitudinal strain in iron Fig. 21 . Fig. 22 . developes reverse thermo-electric qualities in the axial direction and in directions perpendicular to it ; for there can be little doubt but that a lateral traction would produce the reverse effect of a lateral pressure , or that a portion of a linear conductor of iron pulled out on two opposite sides in a direction at right angles to its length , would acquire such a thermo-electric quality as to give rise to currents from stretched to free through hot . But in the former experiment ( S 108 ) it was demonstrated , that when part of an iron conductor is pulled out longitudinally , the thermoelectric effect gives currents fvom free to stretched through hot . The crystalline characteristic is therefore established for the thermo-electric effect of mechanical stress applied to iron , if it be true that traction produces the reverse temporary effect to that of pressure in the same direction . There seems so strong a probability in favour of this supposition , that it may almost be accepted without experimental proof ; but I intend , notwithstanding , to make experiments , for the purpose of explicitly testing it , as soon as some preparations at present in progress enable me to do so . In the mean time I have made the following decisive experiment on the difference of thermoelectric quality in different directions in iron subjected to stress . 116 . A piece of sheet-iron 36 inches long and 16 inches broad , was rolled round two thick iron wires ( J-inch diam. ) , along its breadth at its two ends , and soldered to them . It was cut into narrow slips , each about ' of an inch broad and of different lengths , as shown in the diagram , so as to prevent electric conduction , except along a band about half an inch broad running across the sheet at an angle of 45 ' through its centre . The ends of the slips on each side of this band were clamped ( as shown in the annexed sketch ) between two flat iron bars , but insulated from them by thin pieces of hard wood * , and from one another , where necessary , by pieces of cotton cloth . These bars were each J an inch thick , 3 inches broad , and 30 inches long ; and the two at each side clamped together upon the pieces of hard wood , with the iron slips between them , formed a firm beam , by means of which a considerable stress would be brought to bear on the sheet iron to stretch it in the direction of the slips . The upper of these beams was laid resting with its two ends on the tops of stout wooden pillars , supported below on a very strong wooden bar laid on the stage of a Bramah 's press . The lower double iron beam hanging down and straightening the sheet iron by its weight had strong iron links put over its ends , and an iron bar of about lf-inch square section slipped through them below , so as to hang down a small distance below the roof of the press . Thus , when the press is worked , the upper double iron beam is forced up , and the sheet iron is stretched between it and that the doubts which various writers had thrown on the existence of thermo-electric inversions were groundless , I concluded with certainty that the newly conceived thermal effect of electricity in unequally heated metals really exists . But the theory left it undecided what the absolute nature and amount of this effect may be , and only showed how , by observations on thermo-electric currents , its difference in different metals may be determined . 9 . I therefore had recourse to direct experiment on the thermal effects of electric currents in unequally heated conductors , not to demonstrate the existence of the peculiar effect anticipated , but to ascertain its nature , with moreover a view of ultimately determining its absolute amount , in some particular metal or metals . Before proceeding to describe experiments , by which I have now discovered the quality of the new effect in several cases , I shall , without entering on the mathematical details of the theory , or the full application of Carnot 's principle , repeat in a few words so much of my first communication on the subject to the Royal Society of Edinburgh , as to show the reasoning , founded on incontrovertible mechanical principles , which made me commence the experimental research with the certainty that the property looked for existed , whether I could find it or not . SS 10 to 15 . General inferences regarding the Electric Convection of Heat from Dynamical Principles . 10 . Cumming has discovered that in many cases when one of the junctions of a thermo-electric circuit of two metals is kept at a fixed temperature , if that of the other be elevated gradually from equality , an electro-motive force is produced , which first increases to a maximum , then diminishes , vanishes for a certain temperature of the junction , and acts in the contrary direction with gradually increasing strength as the temperature is further raised . It is clear that , at exactly that temperature of the hot junction for which in any such case the electro-motive force is a maximum , the two metals must be thermo-electrically neutral to one another , and must present reverse thermo-electric relations for temperatures below and above this point . Hence the thermal effect depending on the direction of a current crossing the junction of two such metals must be for temperatures above , the reverse of what it is for temperatures below , the neutral point , and must vanish when the metals are exactly at this temperature . 1 1 . For although Peltier himself supposed the effect he had discovered to depend on the conducting powers of the two metals for heat , and remarked as an anomaly the case of bismuth and copper , for which his supposition was violated , his own experiments show the truth to be , that in a circuit of two metals an absorption of heat at the junction where the temperature is higher , and an evolution of heat at the other , must be produced by the thermo-electric current which is caused by the maintaining of the difference of temperature between the junctions . That this is universally true when the temperatures of the two junctions are on the same side of 4 r2 the lower double iron beam , which is held down by the links and the bar under the roof of the press . Before working the press , the rectangular wooden frame with its iron crosshead is steadied by cords from hooks in the ceiling , and the following arrangements are made : Two slips of sheet iron , each about 18 inches long , are soldered to the upper and lower ends of the oblique conducting channel , and their other ends are soldered to copper wires and put into the circuit of a galvanometer , with the usual precautions ( S 92 ) to ensure equality of temperature and electrical insulation between the two junctions of the dissimilar metals . Four tin-plate tubes , of semicircular section , each about f-inch diameter , and coated with a single fold of paper pasted round it , are pressed with their flat sides on the two sides of the sheet iron against the upper and lower edges of the oblique conducting band ; and are connected by india-rubber junctions , so that steam may be blown through two of them to heat one edge of the conducting band , and cold water sent through the other pair to keep the other edge of the band cold . The arrangements being thus made , a small boiler , heated by a common wiregauze gas-lamp , is used to send steam through one pair of the tubes , and the town-supply water-pipes give a continued stream of cold water through the other pair . When the galvanometer was observed , there was at first no sensible indication of a current . The press was then worked , and the galvanometer immediately exhibited a slight deflection . The press was released , and a careful observation gave again little or no evidence of a current . Then , by an arrangement of double-branched stop-cocks , the steam and cold water were quickly reversed , so that the edge of the conducting band which was hot became cooled , and the other one became heated . Still the galvanometer showed no sign of current until the press was worked , when a reverse deflection to the former was manifested . While the press was kept up the steam and cold water were again sent along the same edges as at first . After a short time the deflection of the needle was reversed , and the same current as at first was indicated . The deflections were very slight in each case , but were unmistakeably demonstrated by the use of the reversing break ( commutator ) connected with the galvanometer . Had it not been for the accident noted above , a much more powerful stress would have been applied to the iron , and I have no doubt but that conspicuous deflections of the needle would have been produced . 1 17 . The current in every case was down the inclined channel of sheet iron when the upper edge was heated , and up the incline when the lower edge was heated . That is , if Fig. 25 . we imagine a rectangular zigzag , from side to side of the bar , instead of the true rectilinear course of the current , the current would be from transversely stretched to longitudinally stretched through hot . Hence it is established by this experiment , that iron , under a simple longitudinal stress , has different thermo-electric qualities in different directions . Knowing , as we do , from the first experiment on copper , described above ( S 107 ) , that iron is not the only metal thermo-electrically affected by stress , we may conclude with much probability that , in general , metals subjected to stresses not equal in all directions will acquire the crystalline characteristic of having different qualities , as regards thermo-electricity , in different directions . 118 . The qualitative investigation of the thermo-electric effects of stress , unaccompanied by permanent strain , that is , the elastic thermo-electric effects of stress , would be complete for iron if the thermo-electric effect of a uniform dilatation or condensation in all directions had been ascertained . I hope before long to be able to carry into effect various plans I have formed with this object in view ; but in the mean time it would be the merest guessing to speculate as to the result . 119 . The establishment of the crystalline characteristic for the thermo-electric effects of stress not equal in all directions , would make it probable that any thermoelectric effects which a metal permanently strained by such a stress can retain after the stress is removed , must also possess the crystalline characteristic . That this is really the case I had in fact proved , before performing the decisive experiment , just described , regarding the nature of the elastic effect , which was only made a few weeks since . The following experiments on the thermo-electric effects of permanent strains in metals were all made more than a year ago . 120 . Well-annealed iron wire was rolled in a coil of about twenty turns on a flat bar of iron |-inch thick and 2 inches broad . The bar was laid on an anvil , with little pieces of thicker wire laid upon it to support the iron core and prevent the lower parts of the coil from being pressed . The upper parts of the coil lying on the upper flat side of the core were hammered till they were all very much flattened . The coil was then a little loosened and drawn off the bar of iron , and a similar wooden core was pushed into it . The ends of the iron wire were arranged , with the usual precautions ( S 92 ) , in connexion with the electrodes of a galvanometer . A piece of hot glass ( not above the boiling-point of water ) was laid along one edge of the coil , so as to heat the iron wire at one set of the points separating hammered from unhammered portions . The galvanometer showed by a great deflection of its needle a current through the iron coil from hammered to unhammered through hot . When the heater was applied at the other edge of the flat coil , the deflection soon became reversed ; still , and always in subsequent repetitions , indicating a current from the strained to the soft metal through the hot junctions . 121 . The coil was next replaced on its iron core , heated to redness in the fire , and cooled slowly . It was then insulated by slipping in paper between it and the iron 5 b2 bar , or by putting it once more on its wooden core ; and it was tested in the galvanometer circuit with the application of glass heaters as before . Not the slightest trace of a current was now found ; a result verifying the conclusion arrived at by Magnus , that it is not peculiarities of form in different parts of a circuit of one uncrystallized metal , but variations in its quality as to mechanical strain , that can ever give it continuous thermo-electric action . 122 . It has thus been proved that a circuit of iron permanently strained by pressure across the lines of conduction acquires the same kind of thermo-electric quality as that which Magnus first discovered to be produced by the lateral pressure compounded with longitudinal traction , which the process of wire-drawing calls into play , or as that which I had myself found to result from a simple traction , leaving a permanent elongation after the force is removed . In all these cases the iron is found to be harder than it was before acquiring the strain , or than it becomes again after being annealed . Hence the nature of the thermo-electric effect in each of the three cases falls under the designation " current from hard to soft through hot " by which Magnus stated his result as regards iron . This is just as is to be expected from the crystalline theory ; since longitudinal extension has a common characteristic with lateral condensation in the theory of strains , and only differs from condensation uniform in all transverse directions , by a certain degree of absolute dilatation which accompanies it , instead of the slight absolute condensation accompanying the lateral condensation as an effect of pressure all round the sides . In fact the agreement between the characters of the thermo-electric effects due to longitudinal traction and lateral pressure , and again between the reverse characters of the effects of permanent longitudinal extension and those of permanent lateral compression established by the experiments which have been described , proves that these effects are due to distorting stress , and to permanent distortion , in the main , and leaves it quite an open question , only to be decided by further experimental investigation , what may be the effects of uniform pressure and of permanent uniform condensations or dilatations . 123 . The crystalline theory is really unavoidable when it is thus established that the effect discovered is due to distortion ; but still , as the one designation " current from hard to soft through hot " applies to all the cases of permanent strain in iron as yet experimented on , I thought it necessary , for removing the possibility of objections , that an iron conductor giving a current from soft to hard through hot , should be constructed . I therefore took twenty-four small soft iron bars turned in a lathe to a cylindrical form Jth of an inch diameter , and each an inch long , with flat ends ; and compressed twelve of them longitudinally in a Bramah 's press , so as to permanently shorten each by about\#163 ; th of an inch . They were then set in a wooden board cut to hold them firmly lengthwise in two rows , those hardened by compression and those left soft , being placed alternately with their ends in contact . The end pieces towards one side were connected with one another by a little slip of iron touching each , and the other ends of the rows were connected with the electrodes of a galvanometer by slips of iron touching them . Each row was firmly wedged up between its terminal iron slips to ensure metallic contact ; but after several attempts , and with all care in cleaning the surfaces meant to touch , no sufficient completeness of contact throughout the circuit could be obtained until mercury was introduced as a liquid solder to connect the pieces of iron . This was done simply by pressing them together as at first , pasting paper round the junctions , and pushing little drops of liquid mercury or small quantities of soft mercurial amalgam into apertures in the tops of these paper coverings . Twelve hollows were cut in the board under and round the junction of the iron bars , each except the last including a pair of ends of the bars in contact in each row , and the last including the ends of the extreme bars on that side and the slip of iron by which they are connected . These hollows were filled alternately with hot sand and cold sand , which was everywhere piled over the junctions ; and the galvanometer gave slight indications of a current , the direction of which through the iron appeared to be generally from uncompressed to compressed , through hot . 124 . The result , however , was not satisfactory ; and it was obvious that the plan which had been adopted for heating and cooling was quite insufficient to sustain the required differences of temperature through so considerable masses of iron ; I therefore had an apparatus constructed for the purpose , consisting of two main pipes of tin-plate , each carrying six smaller pipes and leading to small cells , also of tin-plate , with cylindrical passages through them to admit the iron bars , and with short discharge pipes attached to them on the other side from that by which the former enters . These cells were fitted into the hollows cut for the sand in the board formerly used , the main pipes occupying parallel positions above them on each side several inches from one another . The iron bars , each coated with paper and united as before one to another with mercury solder , were pushed through the hollows of the cells , and were fixed in two rows , with a junction in the centre of each of these hollows , and with the terminals adj usted as before . Cold water from the town supply-pipes was then run into one of the main pipes , so as to flow through the branch pipes and cells connected with it ; and steam from a boiler heated by an ordinary wire-gauze gas-burner was sent through the other system , so as to cool and heat alternately in their Fig. 26 . Fig. 27 . Fig. 28 . order of position the twelve cells with the junctions which they surround . A deflection of the galvanometer needle , amounting to about 4 ' , was now observed ; and when the cold water and steam supplies were interchanged in the two sets of tubes , an equal reverse deflection almost immediately took place . The current indicated was always in many trials from uncompressed to compressed through hot in the iron of the circuit . 125 . Here then we have a case of thermo-electric action in iron giving a current from soft to hard through hot ; not as found before , " from hard to soft through hot . " Hence it is not pieces of hardened iron in general , but the direction of extension or directions perpendicular to the direction of compression , in iron hardened by extension or by compression , that have the thermo-electric quality of deviating from soft iron towards bismuth ; and a line of compression , or ( as we may now safely conclude ) lines perpendicular to a line of extension , have the reverse deviation , that is deviate from soft iron towards antimony , in the thermo-electric series . [ Addition , Dec. 1856 . Subsequently to the reading of the paper , I have , in verification of this conclusion , found , by a direct experiment , that a conductor of sheet iron , hardened by lateral extension and softened in parts , has the thermo-electric property of giving a current from soft to hard through hoti ] The crystalline theory being thus fully established for the thermo-electric effects of mechanical strain in iron , whether temporarily induced during the application of stress , or remaining with molecular displacement after the stress is removed , we may readily suppose it will be found to hold equally for all thermo-electric effects any metal can experience from mechanical action , except the hitherto undiscovered effects of condensations or dilatations equal in all directions . The experiments I have already made on other metals than iron , do not go further in verifying the crystalline theory than to show for copper and tin wires what I had previously shown for iron , that the same thermo-electric effect in a linear conductor is produced by permanent longitudinal extension and permanent lateral compression . 126 . The process of raising to a high temperature and then cooling very suddenly , produces a marked effect on the mechanical qualities of most metals , especially on their hardness ; and generally all that is necessary to do away with this effect and restore the metal to its primitive condition , is to keep it for some time at a high temperature and let it cool slowly . This process being called annealing , I shall for brevity designate as unannealed , any substance which has been subjected to the former process ( sudden cooling ) and which has not been subsequently annealed . It is not easy to judge exactly of the relation of the strains in the different parts of an unannealed piece of metal , to simple mechanical strains ; but some thermo-electric effect , whatever its exact nature and explanation may be , is to be anticipated , with so great a change of other qualities as many metals experience in the process of sudden cooling ; and it may be readily supposed that different thermo-electric qualities will be found in unannealed pieces of different shapes . I have therefore made experiments on the thermo-electric differences between unannealed and annealed linear conductors consisting of round wires , of wires flattened by hammering , and of flat slips , of one metallic substance . 127 . Twisting a wire beyond its limits of elasticity hardens it perhaps as much as traction or hammering , and certainly in every case , when continued far enough , makes the metal very brittle . The nature of the mechanical strain here operative is easily expressed and explained in the theory of elasticity in terms of simple strains different in magnitude and direction in different parts of the wire ; but it is not very easy to judge by theory from the effects of simple strains supposed known , what kind of thermo-electric effect , if any , is to be expected in a metallic wire , with strain thus heterogeneously distributed through it . I have therefore made experiments to determine this effect in various metals . 128 . For experimenting on the thermo-electric differences between annealed and unannealed metallic conductors , a wire , round or flattened , or a slip of the metal was wrapped in a coil of from ten to thirty turns on a wooden core , about 2 inches broad and\#163 ; of an inch thick , or sometimes only an inch broad , with a flat slip of thin sheet-iron laid on one side of it . ' The wooden core was then drawn away , and the coil , held in form by the thin iron core , was heated to redness in the fire , or to some temperature short of its melting-point , in hot oil , and was then suddenly plunged in cold water . After that , one side of the iron core was held over a flame , so as to heat the parts of the coil next it , while the parts of the coil on the other side were carefully kept cool , by the constant application of cold water with a sponge . The wooden core was then slipped in and the sheet-iron removed ; and the coil was ready for testing by the galvanometer . 129 . The preparations for an experiment on the thermo-electric effect of permanent torsion , were commenced by bending a short portion at each end of a length of two or three yards of the wire to be examined , holding these end portions so as to keep the wire between them firmly stretched , and twisting it till it became brittle . It was then wound on a flat iron core ( unless it was too brittle , as often proved to be the case , and then another wire was similarly prepared but not twisted quite so much ) ; the parts of the coil on one side were carefully annealed by flame or hot oil , while those on the other side were kept cool by sponging with cold water . The iron core was then drawn out and the wooden core slipped into its place ; and the coil was ready for testing by the galvanometer . 130 . In making the thermo-electric experiments on the coils prepared in these various ways , glass heaters were first used , but I afterwards substituted two tubes of horseshoe section made of tin-plate and coated with paper , which were applied with their concave parts touching the coil round its two edges . Steam from the small boiler was sent through one of these , and cold water from the town supplypipes through the other . Fig. 29 . The wires used , with the exception of the iron , steel and brass , were all supplied by Messrs. Matthey and Johnson , as chemically pure . The results of the experiments ( made as described in SS 120 and 121 ) on the effects of lateral hammering were , in every other kind of wire tried , the reverse of those found for iron . Thus in steel , copper , tin , brass , lead , cadmium , platinum , zinc , the current was always found to be from the unhammered to the hammered portions through hot . All the wires except zinc were carefully annealed by myself , before they were coiled and hammered ( S 120 ) ; but the process of annealing by heating in oil and cooling slowly made the zinc very brittle and crystalline , instead of softening it as in the other cases , and it was therefore taken as supplied by the manufacturers , and coiled on the core and hammered in the manner described . 132 . The experiments on the coils differently tempered in their different parts ( S 126 ) , in the cases of tin and cadmium , gave only doubtful galvanometer indications ; zinc wire proved so brittle in the annealed parts as to defeat some attempts to test the thermo-electric effects of temper . I have little doubt but that results may be obtained in all these cases by a careful repetition of the experiments , with perhaps some modification to meet the peculiarity of zinc . Slips of sheet iron and of sheet copper were tried without any thermo-electric indication being noticed . [ Addition , Dec. 1856* I have recently found in slips of sheet iron the same thermo-electric effect of temper as in round and flattened iron wires . ] All the other conductors tried gave very decided results . In the cases of round iron wires of very different diameters , of iron wire flattened through its whole length by hammering , of round steel wire , and of steel wire flattened through its whole length by hammering , and of steel watch-spring , the thermo-electric effect of annealing portions of the coil after the whole had been suddenly cooled , was a current from unannealed to annealed through hot . In round wires of copper and brass , the thermo-electric effect of the same process was a current from annealed to unannealed through hot . 133 . The effects of permanent torsion were decisively tested only for iron and copper wires ; and they proved to be in each case the same as the effects of hardening by longitudinal extension , by lateral compression , or by rapid cooling , being quite decidedly from brittle to soft through hot in the iron , and from soft to brittle through hot in the copper . 134 . The views explained above ( S 105 ) , by which I was led to look for the thermoelectric qualities of a crystal in a non-crystalline metal subjected to mechanical strain , show the probability of finding such properties also developed along with magnetism , by external magnetic force , especially in the few metals , iron , nickel and cobalt , which have high capacities for magnetic induction . Towards verifying this idea I tried first the following simple experiment , analogous to the first experiment ( S 107 ) which I had made on the thermo-electric effects of tension . A little helix about 3 inches long , consisting of 220 turns of thin covered copper wire laid on in three strands on a cylindrical core of pasteboard , about J of an inch internal diameter , was slipped upon a piece of thick straight iron wire about 2 feet long , which was supported in a horizontal position by its ends , and through them put in the circuit of a galvanometer . A spirit-lamp was held under the middle of the wire so as to raise it to a high temperature , and then a current from a few of the iron cells was sent through the helix , which was kept a little on one side of the middle of the wire . Immediately the galvanometer needle , which was not at first disturbed by the application of the spirit-lamp , experienced a deflection . The little helix was slipped rapidly through the flame of the spirit-lamp to the other side of the hot part of the wire , and a reverse deflection was immediately produced . It was easy , by moving the helix alternately to the two sides of the hot middle of the wire , to make the needle of the galvanometer to swing through an arc of 10 ' or more . When the needle was brought to rest there was always a most sensible permanent deflection , on one side or the other , according as the helix was left on one side or other of the heated parts . When the circuit of the galvanometer was broken , none of these effects followed from the motions of the helix . They were therefore not due to the direct force of the magnetism in the helix and iron wire , but to that of a current through the galvanometer coil . This always took place in such directions as to indicate a current/ row unmagnetized to magnetized through hot . 135 . The decided character of the result of this experiment established it beyond doubt , that the thermo-electric quality of iron is altered by magnetization . Immediately the question arose ( from the general considerations referred to above , SS104 and 105 ) , are the thermo-electric qualities equally or even similarly affected in all directions ? and the crystalline hypothesis suggested the answer : no ; probably even the reverse thermo-electric effect may be found across their lines of magnetization . As theory could give no more than a conjectural answer , I tried to find the truth by experiment ; and , after various fruitless operations , obtained a very decided result , in the following way . 136 . A piece of thin sheet iron was cut into the shape shown in the diagram , the breadth everywhere being about J of an inch , the length of the longer branch 45 inches , and that oi the shorter 6 inches . In longer branch was.rolled into a plane spiral , on a cylindrical core ^ an inch diameter , the different successive turns being prevented from touching one another by a piece of narrow tape wound on along with the iron slip . The shorter branch , which stood out from the inner end of the coil at right angles to the plane of the spiral , was bent round into this plane , and carried out along one side of the spiral several inches beyond its circumference . Along MDCCCLVI . 5C Fig. 30 . Fig. 31 . with it , a portion of the slip next the other end which was left uncoiled , was carried out from the outer part of the spiral , and cut to such a length as to let the two ends be brought close together . Copper wires , to lead to the galvanometer electrodes , were soldered to these ends , and the junctions of dissimilar metals thus formed were arranged with the usual precautions ( S 92 ) to ensure equality of temperature and electrical insulation . Contrary poles of two steel bars , each about 3 feet long and of rectangular section , 4 inches by ' inch , were placed pressing on each side of the spiral , as shown by the dark shading in the diagram , but insulated from it of course . Four rectangular pieces of thick plate glass , two of them very hot ( perhaps about 300 ' Cent. ) and two cold , were applied , touching the coil on each side , and symmetrically arranged on the two sides of the steel magnets . The galvanometer showed a current in the direction indicated by the arrow-heads . The pieces of hot and cold plate glass were interchanged , and the current became reversed . The magnets were removed , and their effects became scarcely perceptible , or altogether ceased . On repeated trials a current was found always in the direction , from parts of the coil between the magnets towards parts touched by the hot glasses . The experiment was repeated with a powerful electro-magnet , and gave the same result , but not with the same ease , because of difficulties in applying the heaters , &c. 137 . The very strong tendency iron has to assume longitudinal rather than transverse magnetization , when of any form extended in one direction more than in others , was partially done away with by the mutual influence of the different turns of the spiral used in the experiment which has been described ; and the symmetrical arrangement of the heaters was such as to nearly exclude all thermo-electric action , except what is due to the thermo-electric difference between that part of the coil touched on each side by the steel magnets , and the part diametrically opposite . Any thermo-electric effect there may have been from longitudinal magnetization in the parts of the iron ribbon on each side of the steel magnets , must , so far as I could judge , have been contrary to the effect observed . The result obtained , therefore , demonstrates an electro-motive force urging a current from transversely magnetized parts of the iron conductor , through hot parts , to comparatively unmagnetized parts . Hence a transversely magnetized iron conductor deviates from unmagnetized iron towards bismuth , or in the reverse direction to that of the deviation discovered in wire longitudinally magnetized , in the first experiment on the thermo-electric effects of magnetism . It may be concluded , a fortiori , that in uniformly magnetized iron , directions transverse to the lines of magnetization differ thermo-electrically from directions along the lines of magnetization ; and differ in such a way , that if we could get Fig. 32 . an iron conductor of the shape indicated in the diagram magnetized , with perfect uniformity everywhere , in the direction shown by the lines of shading , and if , when the two ends kept at the same temperature are put into the circuit of a galvanometer , the corner is heated , a current would be found to set in the direction shown by the arrow-heads , that is , from transversely magnetized to longitudinally magnetized through hot . 138 . To test and illustrate this conclusion , I took a piece of sheet iron , cut to the shape shown in the diagram , and wound it spirally on a wooden cylinder , prepared with spiral grooves and pipes for steam and cold water , as described below . The oblique edge of the iron , shown on the left boundary in the diagram , being cut at angles of 45 ' and 135 ' to the long edges conterminous with it , was bent in a plane perpendicular to the axis of the cylinder , and thus the long edges of the iron , and the cut separating it into two branches , formed spirals , each at an angle of 45 ' to the axis of the cylinder . The two long edges themselves came very nearly to coincide , the circumference of the cylinder being a little greater in length than the oblique edge of the iron which thus nearly met round it . These two edges , as well as the two edges on each side of the cut between the branches , were prevented from touching one another by being , one at least in each of the contiguous pairs , bound with cotton tape . The projecting slips ( shown on the right in the diagram ) came to positions parallel to the axis of the cylinder , through two diametrically opposite parts of its circumference . Their ends had copper wires soldered to them , and were arranged with the usual precautions ( S 92 ) to ensure electric insulation and equality of temperature between them . The wooden cylinder had two diametrically opposite spiral grooves , each at the same inclination of 45 ' to the axis , and spiral sheet copper tubes , prepared of the proper shape , were slipped into these grooves , and nearly filled up the spaces to the surface of the cylinder . The outsides of these tubes were coated with paper , so as to maintain electric insulation between them , and the sheet iron wound on outside . The wooden cylinder bearing the spiral tubes , and the sheet iron arranged in the manner described , was slipped into the hollow of an electro-dynamic helix , steam was sent through one of the spiral tubes and water through the other , and the copper wires soldered to the ends of the iron slips were connected with the electrodes of a galvanometer . No current was at first indicated . The galvanometer circuit 5c2 Fig. 33 . Fig. 34 . Fig. 35 . the neutral point , cannot , in the present state of science as regards the theory of heat , be reasonably doubted . 12 . If , therefore , a circuit of two metals have one junction kept at the neutral point , and the other at some lower temperature , the current excited will cause the evolution of heat at the cold junction , but neither absorption nor evolution of heat at the hot junction ; and in the rest of the circuit there will be effects either purely thermal , or thermal and mechanical or chemical , according to the nature of the resistance against which the electro-motive force is allowed to work . The source from which the electro-motive force derives its energy to produce these effects cannot be at the hot junction ( S 10 ) , where heat is neither absorbed nor evolved , nor at the cold junction ( S 11 ) , where heat is evolved , nor of course in any uniformly heated part in either metal , through all of which , provided the metal has no thermo-electric crystalline characteristic , there can be nothing but a frictiorial evolution of heat ; that is , it is nowhere but in those portions of the circuit where the temperature varies between that of the cold and that of the hot junction . In those portions , therefore , there must be as much heat absorbed , in virtue of the current , as is equivalent to the aggregate mechanical value of the heat evolved at the cold junction , and all the effects , thermal , mechanical , and chemical , produced in the rest of the circuit . 13 . If , for example , an electro-magnetic engine be introduced into the circuit , and be allowed to work at such a rate as to reduce , by its inductive reaction , the strength of the thermo-electric current to an infinitely small fraction of what it is when the engine is at rest , the heat absorbed in virtue of the current in the unequally heated parts of the two metals will be equal to the heat evolved at the cold junction , together with the thermal equivalent of the work done by the engine , and will be simply proportional to the strength of the current . On the other hand , if the engine be forced to work a little faster , so as to overbalance by an infinitely small amount the thermal electro-motive force , and cause a reverse current in the circuit , there must be heat evolved in virtue of this current in the unequally heated parts of the two metals to an amount equal to the heat absorbed at the cold junction , together with the thermal equivalent to the work done against electro-magnetic forces in the engine . It follows that in the unequally heated portions of the two metals , the current passing from cold to hot in one , and from hot to cold in the other , must produce a thermal effect , in simple proportion to its own strength , constituting on the whole an absorption of heat when the thermal electro-motive force is allowed to produce a current , and an evolution of heat when a current is forced by other means in the contrary direction . 1 4 . Hence , for any two metals which are thermo-electrically neutral to one another at a certain temperature , and which possess reverse thermo-electric properties for temperatures above and below the neutral point , we conclude the following propositions : was broken by its own commutator , and a current was sent through the magnetizing helix . The galvanometer circuit was completed again , and immediately a strong indication of a current through it was manifested . The galvanometer circuit was broken , the magnetizing current reversed , and the galvanometer circuit again completed ; again the same current as before was observed . The steam and cold water were interchanged in the spiral pipes , and the galvanometer current soon set in the reverse direction , with about the same force as before . The magnetizing current was stopped ( the galvanometer circuit being broken for the time and closed again ) , and only slight traces of the current that had been so powerfully indicated could now be observed . 139 . In this experiment the action of the electro-dynamic helix caused the double slip of iron to receive magnetization in lines nearly parallel to the axis of the cylinder ( only a little disturbed in consequence of the gaps between the adjacent edges ) , that is to say , magnetization as nearly as may be in directions at an angle of 45 ' to its length . The sources of heat and cold appliedfalong the two spirals , gave either heat along each of the outer edges of the double slip , and cold along the inner edges between the two branches , or cold along the outer edges and heat along the inner edges . When the ends were connected with the electrodes of the galvanometer , in the case illustrated in the diagram , the current was in the direction indicated by the arrow-heads ; and it was always in such a direction , that if a zigzag line be traced through the two slips from side to side of each , on the whole in the same direction as the current , the changes of direction at the sides of the slips are from transversely to longitudinally magnetized through hot , and from longitudinally to transversely magnetized through cold ; which is the conclusion that was anticipated . 140 . I also experimented on the thermo-electric effects of retained magnetism in steel after the magnetizing force is removed , and obtained very decided results , showing that at least in the case of magnetization along the lines of current , the effect is of the same quality as in soft iron or in the steel itself while under a magnetic force which induces such a state of magnetization . 141 . In one of these experiments , thirty-nine pieces of steel wire , each about -^th of an inch diameter and 2 inches long , soft tempered , were connected by thirty-eight pieces of copper wire , each an inch long , placed between each two of the pieces of steel , and hard soldered to their ends . Pieces of copper wire of the same length were soldered to the outer ends of the first and last pieces of steel , and several feet of steel wire to the ends of each of these . A little electro-dynamic helix was made , 2 inches long and wide enough internally to slide freely over this compound steel and copper conductor ; and by means of it every second piece of the 2-inch steel wires , commencing with the first and ending with the thirty-ninth , were magnetized alternately Fig. 36 . with their poles in dissimilar directions , while the other short wires , and the longer steel terminals , were left as free from magnetism as possible . The magnetizing helix was then removed , and the compound conductor was made into a flat coil on a wooden core ( 2 inches broad and J-inch thick ) , by bending the short copper wires , and arranging the 2-inch steel wires alternately on the two sides of the wood . The terminals were joined , with the usual precautions ( S 92 ) , to the galvanometer electrodes , and one edge of the coil was immersed nearly an inch below the surface of a vessel of oil at the temperature of about 100 ' Cent. Immediately a strong deflection of the needle showed a current , of which the direction in the coil was from unmagnetized to magnetized through hot . When the other edge of the coil was similarly heated , a contrary deflection of the needle as decidedly showed the same thermoelectric difference of quality between the magnetized and the unmagnetized steel wires . 142 . The object of the peculiar arrangement just described , was to prevent the magnetism from spreading to those of the steel portions of the circuit which were to be kept as free from magnetism as possible in order to be compared with those which were magnetized . The introduction of the connecting pieces of a different metal from steel into the circuit cannot give rise to any thermo-electric disturbances * , provided the two ends of each are at the same temperature , a condition which was nearly enough fulfilled in the way the experiment was made , and which was very much favoured by the shortness and the high thermal conductivity of the little copper arcs . The same result was demonstrated in an experiment made with a homogeneous coil of steel wire , of which parts had been magnetized , by ordinary steel magnets , before it was bent on the core . [ S 143 . Received May 10 , 1856 . ] S 143 . Experiment . On the Effect of Magnetization on the Thermo-electric Quality of Nickel . Through the kindness of Dr. George Wilson , I have been able to experiment on a bar of nickel , about ' an inch in diameter and about 8 inches long , in the form of a horse-shoe magnet , belonging to the Industrial Museum of Edinburgh . The accompanying sketch and description show the plan of the experiment . Description of Sketch . N , nickel horse-shoe . B B , double tubes of sheet copper , electrically connected with one another by a copper band , and insulated from the nickel by silk paper , laid on with shelllac varnish ; serving to drain all electrical leakage from the magnetizing coil , without causing the slightest sensible current through the nickel , and serving also to convey a stream of cold water to maintain the lower parts of the two branches of the horse-shoe at as nearly as possible equal temperatures . Fig. 37 . AA A , india-rubber pipes to lead a stream of cold water through the coolers . C , magnetizing coil , wrapped on one of the copper coolers . E E , electrodes of magnetizing battery of twenty iron cells , charged with nitric acid , &c. F , commutator for interrupting and reversing the connexion between the magnetizing battery and coil , or reversing the current , M M , mercury cups , in which the extremities of the nickel were immersed ( mercury being both very convenient for the purpose , and the metal least thermoelectrically removed from nickel of all that have been tried by any experimenter ) . m m , mercury electrodes joining copper galvanometer electrodes D D , at G G. K , commutator for interrupting and reversing the connexions of the galvanometer electrodes . Heat was applied at HH by means of a gas-lamp and blowpipe . A current from magnetized to unmagnetized through hot , was indicated by a considerable galvanometer effect , which , by management of the galvanometer break , K , was readily directed to give oscillations of the needle through three or four degrees . The same conclusion had been indicated in several previous attempts , with various defects of arrangement remedied in the experiment just described . In this last experiment the result was made most manifest ; and , being completely separated from all effects of induced currents ( which were quite insensible ) , of electrical leakage , and of unequal heating of the junctions of mercury and nickel , and of the junctions of mercury and copper , was set beyond all doubt , I therefore conclude , that longitudinally magnetized nickel in a thermo-electric circuit deviates from nickel not under magnetizing force , in the same direction as bismuth . This is the reverse of the deviation which I formerly found to be produced in iron by longitudinal magnetization . 144 . The results of the various experiments which have been described in Part III . are collected in the following Tables . Table I. Effects of Stresses and Strains on the Thermo-electric Qualities of Metals . DCon(fuctor()f Thermo-electric Order reckoned from Bismuth towards Antimony . Iron I Free Under longitudinal traction . ! Iron Free Under transverse compression . Iron Under transverse traction Under longitudinal traction . Iron Permanently strained by longitudinal Soft Permanently strained by longitudinal traction , and left free from stress . compression , or by lateral extension , and left free from stress . Iron Hardened by transverse hammering ... I Soft Hardened by longitudinal hammering . Round iron wires of Made brittle by twisting I Annealed after being made different diameters . | brittle by twisting . Round and flattened Suddenly cooled I Annealed . iron wires . | Steel wire Some specimens flattened by transI Soft Other specimens flattened by transverse hammering . j verse hammering . Round and flattened Hardened by sudden cooling Annealed . steel wires . Steel watch-spring. . Hardened by sudden cooling Annealed . Copper Under longitudinal traction Free . Copper Soft I Permanently elongated by longitudinal I| traction , and left free from stress . Copper Soft Hammered transversely . Round copper wire. . I Annealed after being made I Made brittle by twisting . I brittle by twisting . | Round copper wire. . Annealed Suddenly cooled . Platinum Under longitudinal traction Free . Platinum Soft Hammered transversely . Tin Soft I Permanently elongated by longitudinal I traction , and left free from stress . Tin Soft Hammered transversely . Brass Soft Hammered transversely . Round brass wire Annealed | Suddenly cooled . Cadmium Soft Hammered transversely . Lead I Soft Hammered transversely . Zinc Soft Hammered transversely . Table II . Effects of Magnetism on the Thermo-electric Qualities of Iron and Nickel . DCSCndutctorOf Thermo-electric Order reckoned from Bismuth towards Antimony . _________ i. __ Iron Under transverse magnetizing force ... Free I Under longitudinal magnetizing force . Steel Unmagnetized Retaining longitudinal magnetization . Nickel Under longitudinal magnetizing force . Free . PART IV . METHODS FOR COMPARING AND DETERMINING GALVANIC RESISTANCES , ILLUSTRATED BY PRELIMINARY EXPERLMENTS ON THE EFFECTS OF TENSION AND OF MAGNETIZATION ON THE ELECTRIC CONDUCTIVITY OF METALS . 145 . In endeavouring to discover the effects of magnetization and of mechanical strain on the electric conductivity of iron and other metals , I was led , from trying various more or less obvious methods for testing resistances , to use a differential galvanometer of a very simple kind , which I constructed for the purpose . I shall give no description of this instrument , as I now ( Nov. 1856 ) find it in one important quality inferior to the differential galvanometer first constructed and used by M. Becquerel* , and I do not know that its peculiarity has compensating advantages . I mention it only because it was with it that I made nearly the first of my trials to find the effects of magnetism on the electric conductivity of iron , and the very first by which I obtained a decided result . 146 . In these experiments I used two covered iron wires , each several yards long , coiled into circles about 4 inches diameter , as the two resistance branches in the divided channel through the two conductors of the galvanometer . Magnetizing one of them tangentially by means of a coil of covered copper wire wound on a copper sheath soldered round it as an electric drain , I ascertained , on the 23rd of April , 1855 , that the electric conductivity of iron wire is diminished by longitudinal magnetization . The arrangement however proved , as I anticipated , to be of a very unsatisfactory kind ; and the needle kept moving across the field in one direction almost steadily , during the whole time the current was sustained through the tested conductors , which was for several hours . Continually more and more resistance had to be added to the conducting channel containing the iron wire round which there was no magnetizing coil , to keep the needle within range . After the magnetizing current had passed for some time , this variation of the needle went on more rapidly , and called for more frequent adjustment by the additions to the other branch . All this was just as must be expected ; and my reason for not introducing currents of cold water round the two iron coils , to maintain them in precisely similar thermal circumstances , was that the tubular systems required for the purpose could not be easily made , and that I thought I might find out the nature of the result in the first * Annals de Chimie et de Physique , tome xvii . 1846 . instance , notwithstanding the imperfection of the arrangements . In this hope I was not disappointed . The glass needle ( carried by the little suspended magnet , which was only about ^ an inch long ) , while moving steadily across its field , would receive an impulse forward and make two or three very rapidly diminishing oscillations , when the current was started through the magnetizing coil : when the current was suddenly reversed , the needle would show little or no indication of any effect : when the current was broken , it would make a start backwards , and after two or three oscillations would continue advancing as before , perhaps rather more rapidly . Traces of induced currents in the iron coil under the influence of the magnetizing helix were exhibited by scarcely perceptible differences in the bearing of the needle , according as the current was made in one direction or the other , and by slight impulses it received when the magnetizing current was suddenly reversed . After the current had been kept up for some hours through the iron wires , and when , partly by the heat developed by the magnetizing current during the periods of its flow , and partly by heat conducted from the iron wire within , the outside of the magnetizing coil had become very sensibly hot to the touch , the variation of the needle in the galvanometer became much less rapid than at first ; and tolerably satisfactory indications , amounting to a fraction of a degree of permanent deflection , showed with perfect consistence an increase of resistance in the iron wire under magnetic force when the magnetic current was sustained in either direction , and a diminution of resistance in the same iron wire following immediately a cessation of the magnetizing current . 147 . I followed the same method in a first attempt to find the effect of transverse magnetization on the electric conductivity of iron ; two spirals made on the plan described above ( S 136 ) being used as the resistance branches in the two channels conveying the divided current , and one of them placed between convex poles of a Ruhmkorff electro-magnet . The induced currents in making , reversing , and breaking the magnetizing current were of course most conspicuously indicated by the galvanometer needle , but the needle came to rest after a few oscillations ; and then it did not exhibit any deviations of a sufficiently marked character , when the direct effect of the electromagnet ( which by a very troublesome process of shifting the position of the magnet , was reduced as much as possible in preliminary arrangements , ) was eliminated by reversals , to allow me to draw any decided conclusion as to the effect of the magnetic force on the conductivity of the iron spiral across which it acted . 148 . Before carrying into execution various obvious improvements in the experimental arrangements just described , or applying the system with the differential galvanometer to other investigations , I began to think of Maggi ' s experiment * on the relative thermal conductivities of a magnetized iron disc in directions across and along the lines of magnetization . As the electrical analogue , the method which Matteucci , and I believe Kirchhoff and others , have used in tracing equipotential lines on the surface of a conductor traversed by an electric current , occurred to me . Six months later , I thought of the multiplying branch ( first used in the experiment described in S 161 below ) to render available the sensibility which a powerful current through the body to be tested , with the use of a moderately sensitive galvanometer , must obviously give to that method when applied to the investigation of differential effects on the electric conductivity of a body in different directions ; and I succeeded with great ease in making very satisfactory experiments ( SS 161 to 165 below ) by means of it , which first decided the question as to whether or not the effects of magnetization give different electric conductivity in different directions to a mass of iron . At first , however , I did not see this or any other way to render the method practicable with galvanometer electrodes , either moveable upon the sheet of metal to be tested ( in which case a motion of T^th of an inch would drive the needle from an extreme deflection on one side to an extreme reverse deflection ) , or by electrodes soldered to points on an equipotential line ( in which case a slight alteration in temperature in different parts of the plate might drive the needle irrecoverably to an extreme deflection on one side or the other ) ; but the experiments which I knew as having been made by Matteucci suggested to me the following very simple plan , which I immediately commenced trying , and which I have since found applicable with the greatest ease to a variety ( I believe now to every variety ) of experiments on electric conductivities * . 149 . Let AB be the conductor to be tested , and let CD be another of nearly equal resistance , either a piece of the same wire continuous with the other through an arc BC , or connected with it by a thicker arc of copper , or of another metal , as may appear convenient for the particular case treated . Sometimes the experiment is arranged to test differential effects experienced alternately or simultaneously by AB and CD . But when one of them , AB , alone is acted upon , with a view to varying its resistance , it alone may be regarded as the conductor which is tested ; and the other , CD , will then be called the reference conductor . Let a wire , AOPD , which will be called the testing conductor , be soldered by its ends to the ends A and D of the conductor to be tested and of the reference conductor , or to strong pieces of metal to which those ends are firmly attached . Let one electrode of a galvanometer be soldered to the connecting arc BC , at its middle , or at any other point of it , Q ; and let the other galvanometer electrode be ready to be applied by the hand to any position on the testing conductor . A current is then sent from one or more cells of Daniell 's battery through electrodes connected with A and D. This current flows through the divided channel ABCD and AP'OPD , in quantities inversely proportional to the resistances of the two parts . The moveable galvanometer electrode is then applied , first to one point and then to another of the testing conductor ( care being taken not to reverse , nor even to diminish , the magnetism of the lower needle in the astatic system of the galvanometer * ) , until by trial the point O that may be touched without producing any deflection in the needle , is found . The influence to be tested , whether it be magnetization , or tension , or elevation of temperature , is then applied to AB , or the influences to be tested against one another are applied to AB and CD , and the moveable galvanometer electrode is ( if it has been removed ) again applied at O. If the needle remains undisturbed , no effect is indicated ; that is , no alteration in the resistance of ABQ , or only an alteration in the same proportion as an alteration experienced by QCD , has been indicated . If , however , a deflection is observed , in such a direction that the moveable electrode must be moved to some point P in the part OD , it is inferred that the ratio of the resistance of ABQ to that of QCD has been increased ; or on the other hand , if such a deflection as requires a motion of the moveable electrode to a point Pf in OA , the resistance of AB has been diminished relatively to that of CD . 150 . As an example , I shall describe an experiment on the relative effects of tension on electric conductivity in copper and iron wires . Two pieces of stout copper wire , A , D , were each twisted into a loop which was made fast by solder ; a couple of inches towards one end of each wire being left free from the twisted part . These loops were put upon a strong hard wood peg about f of an inch diameter , at a distance of about J of an inch from one another ; and to their lower ends were firmly soldered fine iron and copper wires ( strong enough to bear weights of about 8 lbs. and 5 lbs. respectively ) . These wires were cut to the same length of 4J feet , and their lower ends were put into slits about ~ of an inch deep , cut in the top of a piece of stout copper slip of the form and dimensions shown in the diagram , and the copper pressed upon them to hold them fast by a pair of pincers . Solder was then applied , to make a complete and compact metallic connexion between the wires and the copper piece . A testing conductor , consisting of seven yards of No. 18 copper wire , was soldered by its ends to the upper copper pieces A , D ; and a current from six small cells of Daniell 's was sent through the double channel by electrodes soldered a little higher up to the same copper pieces , A , D. One galvanometer electrode was soldered to the lower copper piece , and the other was applied to the testing conductor till the point O , equipotential with the point of attachment of the former , was found . As from previous experiments I knew that an accidental variation of jTToth 'f an inch in the position of the moveable electrode on the testing conductor might lose or overbalance the effect looked for , I added a multiplying branch , TFO'EU , consisting of a yard of No. 18 copper wire , with its ends soldered about half an inch on each side of O. This , of course , when touched by the moveable electrode , gave about thirty-six times the motion that would be required to produce or to correct any effect on the galvanometer if the simple testing1 conductor were used . The point O ' , on the multiplying : branch , that could be touched without giving any deflection was then found ; and weights were hung from the lower end of the lower copper piece , so as to stretch the copper and iron wire equally . Immediately a deflection of the needle in the galvanometer showed a current . This was corrected by sliding the moveable electrode on the multiplying branch towards U , that is , towards the parts conterminous with the copper wire . When the weights were removed , immediately a reverse deflection was observed . The conclusion is , that iron and copper wire equally extended have their resistances altered differently when under the stress ; that of the iron wire being more increased , should the absolute effect in each wire be an augmentation of resistance , as other experiments I have made give me reason to suppose it is , or less diminished should it turn out that the absolute effect in each wire is a diminution of resistance . 151 . Again , a heavier weight was applied so as permanently to elongate the wires . direction to the system . The strongest current through the coil only confirms the required state of magnetization , provided when it is started the index is either at zero , or on the side of zero towards which the deflection is to be . If by accident a powerful current is admitted through the coil when the index is on the wrong side of zero , the lower needle has its magnetism instantaneously reversed ; but it may be as instantaneously put right again by suddenly reversing the current . If\#171 ; at any time , from the lower needle having either lost magnetic moment , or acquired a reverse magnetization , the astatic system is found reversed , it may be put in order with ease either by simply sending a powerful current through its coil , or by doing so and then suddenly reversing the current . Fig. 40 . The deflection , which was in the same direction as at first , was noted , but not corrected by any motion of the moveable electrode , and the weight was again removed . The needle returned towards zero , but remained deviating in the same direction as it had done to a greater degree with the weight on . By applying the hand instead of weights and gradually pulling down the lower copper piece , at first slowly , and afterwards rather faster , the needle could be made to deviate to 7 ' and kept steadily there . After the wires had been stretched by rather more than an inch , the hand was removed with a gradual diminution of stress , which could easily be regulated to let the needle down without oscillation to whatever position it would rest in , with the stress entirely off . This in several repetitions of the experiment on the same wires was found to be somewhere about 3 ' or 4 ' in the same direction as the deviation which was kept at 7 ' for a few seconds during the stress . Hence it was further concluded , that , as regards electric conductivity of the substance , the effect of permanent elongation , remaining after the stress is removed , differed between iron and copper in the same way as the effect of longitudinal stress during its action ; that is , that the galvanic resistance of iron is more increased by permanent elongation than that of copper . Irregular variations to a considerable extent , obviously due to thermo-electric effects from the copper and iron in the compound conducting circuit , made me not attempt to measure with much care , the distance the moveable electrode had to be shifted to counteract the effects of tension ; but I intend repeating the experiment and making it for other pairs of metals , with this source of irregularity removed by a modification of the testing conductor . 152 . In the kind of experiment which has been described , the channels through the two metals experienced exactly the same elongation , and , it may be said without committing any sensible error , the same narrowing , by the longitudinal extension . The effect observed , therefore , depends truly on variations in the conductivities of their substance . I had made previously various experiments on copper wire alone , and on iron wire alone , in which I attempted to eliminate the effects of elongation and narrowing , and had very nearly established , for the case of iron wire at least , that the augmented resistance due to tension , either temporary or permanent , is a very little more than can be accounted for by the change of form . As , however , I have other experiments in progress , by which I hope to be able to show for a single metal the absolute effect on its specific conductivity separated perfectly from any influence on the resistance of the conductor occasioned by a change of its form , I defer in the meantime giving more details of investigation on this subject . 153 . The method which has now been described has many great advantages over that by the differential galvanometer , or any other that I know of for testing or measuring galvanic resistances . In the first place , the irregularities , dependent on the electrodes , connexions , and circular conductors , of the differential galvanometer , are entirely done away with , and only the tested and the testing conductors , all connected by compact solderings , can influence the indication from which the results are In one or other of the metals ( and most probably in both ) there must be a thermal effect due to the passage of electricity through a non-uniformly heated portion of it , which must be an absorption of heat or an evolution of heat , according to the direction of the current between the hot and cold parts , and proportional in amount to the whole quantity of electricity that passes in a stated time . ( 2 ) The amount of this effect , with the same strength of current and the same difference of temperatures , must differ in the two metals to such an extent , that the effect of a current in passing from cold to hot in one metal , together with the effect of an equal current passing from a place equally hot to a place equally cold in the other , may amount to the absorption or evolution , the existence of which has been demonstrated . 15 . The reversible thermal effect* of electric currents in single metals of nonuniform temperature , which has been thus established , may obviously be called a Convection of Heat by electricity in motion . To avoid circumlocution , I shall express it that the Vitreous Electricity carries heat with it , when this convection is in the " nominal direction of the current . " On the other hand , when the convection is against the " nominal direction of the current , " it will be said that the Resinous Electricity carries heat with it . SS 16 to 18 . Dynamical Theory applied to draw , from thermo-electric data , inferences regarding the Electric Convection of Heat in Copper and in Iron . 16 . The application of the preceding theorem to the particular case of copper and iron is a consequence of Cumming 's discovery , that , if one junction in a circuit of two arcs of those two metals be kept cold , and the other be heated gradually , a current at first sets from copper to iron through the hot junction with increasing strength ; but begins to diminish after a certain temperature , which Becquerel found to be about 300 ' Cent. , is exceeded ; falls away to nothing when a red heat is attained ; and sets in the reverse -fdirection when the elevation of temperature is pushed higher . to be drawn . In the second place , the galvanometer circuit may be broken and completed , and reversed , as often as is desired , by its own commutator , without affecting to the slightest sensible degree , the strength of the current through the tested and testing branches ; while in the former mode of experimenting the indicating needle was always under the action of the divided current , unless the current in one or the other of the branches was broken , which introduced irregularities lasting for a considerable time , by the consequent changes of temperature through the conductors . This was an immense convenience in every experiment , and allowed small deflections , amounting to the tenth of a degree , to be tested with ease by using the commutator of the galvanometer , and getting oscillations . But it was of especial advantage in the experiments on the effects of transverse magnetization , since the galvanometer circuit had only to be kept broken for a few seconds during the making , breaking , or reversing of the magnetizing current , to get entirely rid of all disturbances of the needle due to induced currents ; and in all experiments in which the Ruhmkorfp magnet was used , since by breaking the galvanometer circuit and using a little steel magnet in the hand , the galvanometer needle could be let down in a few seconds into its position as affected by the direct action of the large magnet , before proceeding to test the current due to the change of resistance under investigation . In the third place , it is possessed of almost unlimited capacity for increase of sensibility . In some of the experiments on the influence of tension on electric conductivity , I have tested with the greatest ease effects amounting to only TB-oiioth of the whole resistance of the wire under examination , and I see no difficulty in testing effects amounting to only the tenth part of that , or even hundreds of times smaller effects , by using more powerful currents , and applying artificial means to keep the wires cool . PART V. ON THE EFFECTS OF MAGNETIZATION ON THE ELECTRIC CONDUCTIVITY OF METALS . 154 . The remarkable effects which I found produced in the thermo-electric quality of a metal by magnetization and by mechanical strain , appeared to render it highly probable that the same agencies would also influence their electric conductivities . To demonstrate this if I could , and to discover the nature of the anticipated effects , I commenced an experimental investigation of the subject , and , after various nugatory operations , arrived at a variety of positive results by the following processes . 155 . Exp. 1 . On the longitudinal electric conductivity of longitudinally magnetized iron wire . A length of seventy-two yards of silk-covered copper wire was rolled in six strands , or altogether in about 860 turns on a core made up of two concentric brass tubes , connected at their ends by a ring of sheet brass , and arranged to have water sent through the space between them by suitable entrance and exit pipes soldered to apertures in the outer one ; the external diameter of the brass tube was about ^ inch , and the internal diameter of the inner one about\#163 ; inch ; the metal of both outer and inner tubes being as thin and as well smoothed as it could be got . The piece of iron wire to be tested was soldered at one end to a piece of thick copper wire , and then insulated by a thin coating of writing-paper , wrapped twice round it , and pushed into the inner brass tube , which was just large enough to admit it easily . A second iron wire of equal dimensions was similarly prepared and inserted in a second core , in all respects like the other , except that in this experiment it had no copper wire wrapped round it . The two cores being laid side by side , the free ends of the iron wires were connected as shown in the diagram , by an arc of thick copper wire , C , soldered to them . A current from a single large cell of Daniell 's was admitted and carried off by the electrodes A and B. Cold water was kept constan tlyr flowing through the spaces between the concentric brass tubes round the iron wires . The testing conductor ( S149 ) used in this experiment consisted principally of the following parts : ( 1 ) Two pieces of No. 18 copper wire , each sixteen yards long , prevented from touching one another by a piece of twine between them , rolled together on a thin copper cylinder , 12 inches long and 3 inches diameter , from which they were insulated by a coating of two folds of silk ploth sewed round it . ( 2 ) Soldered to two of their contiguous ends , a connecting arc of thick copper wire , which was at first intended to be graduFig . 41 . ated , and will be called the scale of the testing conductor . ( 3 ) Separate short thick wires soldered to the other ends of the wires coiled on the copper cylinder , to bear binding screws for making connexions with the electrodes A and B of the conductor to be tested . One electrode of the galvanometer was soldered to the middle of the connecting arc between the two iron wires , and the other was held in the hand , and applied about the middle of the scale of the testing conductor . A rather troublesome process was then required to bring the galvanometer to zero by adding resistance on one side or the other between the ends of the testing conductor and A or B. When this was done , it was found that great deviations of the galvanometer needle were produced by sliding its moveable electrode a few inches in either way on the scale , and a perfectly sensible deflection by sliding it as much as ^th of an inch . The point of the testing scale to which the moveable electrode had to be brought , to give no deflection of the galvanometer , was determined : the circuit of the galvanometer was broken , and a current from six of the small iron cells was sent through the magnetizing coil . Immediately on completing the galvanometer circuit again , with its electrode held on the same point of the testing scale as before , a very considerable deflection was observed . On breaking the galvanometer circuit , reversing the magnetizing current , and completing the galvanometer circuit again , the same deflection was observed ; and when the magnetizing current was stopped the galvanometer again gave zero , or nearly so . On repeating the process as regards the magnetizing current , without breaking the galvanometer circuit , the same deflection was always observed , in whichever direction the current was sent through the magnetizing coil ; and little or no either instantaneous or permanent effect was produced on suddenly reversing this current . It was found that the deflection occasioned by the magnetization was diminished by sliding the moveable electrode along the scale from its end communicating with B , towards its end communicating with A , and was corrected by such a motion through a space of about f ths of an inch ; equivalent to y^th of an inch of the No. 18 wire , constituting the chief part of the testing conductor . It was concluded that the iron wire had its electric resistance increased by magnetization , and that this augmentation amounted , in the particular experiment , to about so ou 'f 'he whole resistance of the magnetized piece . 156 . Exp. 2 . On the effect of permanent magnetization on the electric conductivity of steel wire . The same apparatus as in Experiment 1 was used , and was in all respects similarly arranged , except that hardened steel wires as free from magnetism as possible were substituted in place of the soft iron cores in the brass tubes . On bringing the galvanometer to zero and sending a current through the magnetizing coil , the same deviation as before was observed , and a much smaller deviation in the same direction remained after the magnetizing current ceased . This experiment was repeated several times on fresh unmagnetic steel cores , and always with the same result . I concluded that steel when subjected to magnetic influence has , like iron , its electric conductivity diminished in the direction of the lines of force ; and that it retains some of the same effect with the permanent magnetism subsisting after the magnetizing force is removed . At the same time I was not quite satisfied with the experiment , as the galvanometer needle was never very steady , and , to keep it about zero , the moveable electrode had to be shifted largely along the scale , sometimes quite to one end , when , to get it on the scale again , additional adjustjnent wires had to be added to the other branch of the testing conductor . This prevented me from using more powerful currents through the wires to be tested and so getting larger indications of the results ; but I determined if possible to repeat the experiment afterwards with arrangements better adapted to do away with all variations in the conductivity of the circuit except those under investigation . I still keep it in view to do so , and I have no doubt now of being abie to get rid of all the unsteadiness which I had found so troublesome . Exp. 3 . Attempt to discover the effect of transverse magnetization on the longitudinal conductivity of a slip of sheet iron . Two brass cores like those described above , and of the same length ( 10 inches ) , but of larger inner and outer diameters , were prepared , and a quantity of covered copper wire rolled on one of them in four strands , or in all 570 turns . Two slips of sheet iron , each 7 feet long and . S. inch broad , were wound upon single brass tubes coated with paper , and the successive spires of each were kept from contact by a piece of twine wound on between them . A length of 9 inches of each brass tube had 84 inches of the slip iron laid upon it , and therefore the inclination of the helix to a plane perpendicular to its axis was about 6 ' , being the angle whose sine is -^ . Each of these iron spirals was protected outside with a coating of paper , and pushed into the interior of one of the brass cores . A copper arc , C , was soldered to each of them so as to connect their extremities on one side , and powerful copper electrodes , A and B , were soldered to their other extremities . Then , a stream of water being kept constantly flowing through each of the inner tubes and through the spaces between the concentric brass tubes outside , a current from a large cell of Daniell 's ( S 63 ) ( exposing 25 square feet of zinc to 4*4 square feet of copper ) was sent through the iron spirals , and a testing conductor ( the same one as before ) was put in comFig . 42 . munication with their electrodes , A and B. One electrode of the galvanometer being , as before , soldered to the middle of the copper arc connecting the iron spirals , the other was applied to the scale of the testing conductor . The galvanometer being brought to zero by the insertion of adjustment wires at one end or other of the testing conductor , it was found to be rather steadier than in the former experiments , probably because of the diminution of thermal effects by the stream of water through the cores , and the greater surface of iron exposed outside and inside to refrigeration . When a current was sent and maintained through the magnetizing helix , a very decided permanent deflection was occasioned in the galvanometer ; and this the same with each direction of the magnetizing current . If the galvanometer circuit was kept complete , its needle experienced a powerful impulse , sending it through a great many degrees in one direction or the other at the instant of starting , or of reversing , or of stopping the magnetizing current , but quickly in each case showed the nature of the permanent deflection by oscillating about one position , when the current was steadily maintained , in either direction . These impulsive deflections were of course due to induced currents , and were entirely prevented by keeping the galvanometer circuit broken during the starting , the reversal , or the stoppage of the current through the coil of the electro-magnet . 158 . The deflection due to the effect of magnetic force on the substance of the iron was corrected in each case by sliding the moveable electrode towards the part of the testing scale remote from the end connected with the iron spiral which experienced that effect ; and it therefore indicated a diminution of conductivity in the iron . 159 . If the lines of magnetization had been exactly perpendicular to the lines of electric current through the iron , we should now conclude that transverse magnetization diminishes the conductivity of an iron conductor ; that is , that it produces the same kind of effect on the conductivity as longitudinal magnetization . But the lines of current formed spirals inclined at an angle of 84 ' to the lines of the magnetizing force ; and the mutual influence of the consecutive parts of the magnetized iron spiral would have an effect ( not wholly compensated by the mutual influences between the successive spires because of the thickness of the twine between them , ) contributing to longitudinal magnetization ; and therefore the lines of magnetization must have been inclined , not at 90 ' , but at some angle less than 84 ' , to the direction of the lines of current . Hence all we can conclude is , that not only longitudinal magnetization but oblique magnetization up to some angle of obliquity less than 84 ' from the lines of current , diminishes the electric conductivity of iron . 160 . It remains to be determined by experiment what is the effect of magnetization right across the lines of current : if a diminution of conductivity , whether a greater or a less diminution than is caused by an equal longitudinal magnetization ? or if it is an increase of conductivity , what is the angle of obliquity of the magnetization which gives neither increase nor diminution of conductivity ? ? 161 . Exp. 4 . To discover the differential effect of magnetization on the conductivity of iron in different directions . A square of 1^ inch each side was cut from thin sheet metal , and powerful electrodes were soldered to two corners , A and B. A reference electrode ( S 149 ) of No. 18 copper wire was soldered to C , one of the other corners , and the two extremities of a yard of the same kind of wire , to be used as a multiplying branch , were soldered to points D , E , about ^th of an inch from one another on each side of the remaining corner . A current being conducted through the square by the principal electrodes A and B , the reference electrode was used to connect C permanently with the commutator belonging to the testing galvanometer . Another wire used as a testing electrode , was applied to connect any point of the plate , or of the multiplying branch , with the other galvanometer electrode . In the first place , it was found that a powerful current was raised in the galvanometer coil if the testing electrode was applied to any point of the multiplying branch ; and it was necessary therefore , as was anticipated , to adjust the distribution of resistance through the square by filing , so that there might be some point on the testing branch which would give no current when touched by the testing electrode . ( See below , S 176 , where a less troublesome way of managing this part of the arrangement , in an analogous experiment , is described . ) For this purpose , in the first place the testing electrode was applied at different places along the edges BD , EA of the square till a point was found which gave no deflection of the galvanometer . If this was in BD , the plate had to be thinned in its middle parts parallel to CA and BD , or else to be thinned along the edges CB , AD , so as to increase the resistance to conduction parallel to the last-mentioned edges . Or if the neutral point was in EA , the plate had to be thinned in its middle parts parallel to CB and AD , or along its edges BD , CA . By using the file according to these directions , after a few trials the neutral point was brought upon the testing branch ; that is to say , the resistance was so adjusted in the square that the line from C cutting right across the lines of conduction , or which is the same thing , the equipotential line through C , passed between D and E. A piece of sheet copper as broad as the iron square , but rather longer , was bent as shown in the diagram , so as to give a depressed space in which the iron , insulated from the copper simply by a piece of writing-paper , could rest steadily . This copper cradle was placed resting on the flat poles of a Ruhmkorff electro-magnet , which were pushed together so as to hold it firmly . Any leakage of electric currents from the coils of the electro-magnet was thus effectually drained by the copper , so that a simple sheet of paper was quite enough to do away with all sensible indications of currents in the iron acquired otherwise than through the electrodes A and B. [ This electrical drainage would be made more nearly perfect by using paper or some other non-conductor to separate the cradle from the poles of the magnet . ] 162 . A large single element of Daniell 's ( S 63 ) , consisting of seven zinc plates in 5e2 Fig. 43 . Fig. 44 . Fig. 45 . seven porous cells , contained in four large wooden cells , and exposing in all 8#75 square feet of zinc surface to 15#3 square feet of copper , was then used to send a current through the iron square , insulated between the poles of the electro-magnet , in the manner described . 163 . The neutral point on the testing branch being got by trial , it was found to remain tolerably steady , although no doubt during the first minutes of the flow of the current it may have varied much , as the iron got heated , which it soon did to a degree very sensible to the touch . Moving the electrode along the testing branch through a quarter of an inch on either side of the neutral point , gave a very marked deflection of the galvanometer . The galvanometer circuit was then broken , and a current from six of the small iron cells was started through the coils of the electro-magnet . When the galvanometer circuit was again , after a few seconds , closed , with its electrode on the same point of the multiplying branch as before , a very considerable deflection was observed in the needle . To correct this deflection and bring the needle to zero , the testing electrode had to be moved to a position 2 or 3 inches nearer D on the testing branch . 164 . The new neutral point was unchanged when the electro-magnet was reversed , and when the magnetizing current was broken there was a permanent deflection in the galvanometer the reverse of that observed when the current was started in either direction . If the galvanometer circuit was completed within a second or two of any of the changes in the magnetizing current , the needle experienced , obviously from induced currents , powerful impulses in one direction or the other , according to the direction of the current made or unmade through coils of the electro-magnet . But in every case , although from various disturbing causes the neutral points gradually shifted largely along the testing branch , the permanent effects of making and of unmaking the electro-magnet were most marked , and were uniformly as stated above . 165 . Thus it appears that magnetization shifts the equipotential line through C from its position running across to the opposite corner , to a position ( dotted in the diagram ) a little nearer CB ; so much so that its end is shifted about ^X^o , or ^th of an inch from E towards D. This shows that the passage of electricity in the directions AE and CB has become less resisted than it was , relatively to the passage in the directionsL AC , DB ; and it therefore follows that the electric conductivity of magnetized iron is greater across than along the lines of magnetization . Fig. 46 . Fig. 47 . Still , as the preceding experiment ( Exp. 3 ) had appeared ( S 159 ) to show that the absolute conductivity is diminished in all directions by magnetization , it seemed possible that the effect now observed might be caused by inequalities in the distribution of magnetism in the plate . Thus if from the character of the distribution of the magnetizing force , or because of non-uniformity in the plate , the parts between C and B and between A and E were less intensely magnetized , and those between C and A and between B and D more intensely magnetized , than the average , the observed effect could be accounted for without any difference in the electric conductivity of the substance in the different directions . To test this conceivable explanation , pieces of soft iron ( cubes and little square bars nearly double cubes ) were laid over the square plate , being kept insulated from electric communication with it by paper , so that while the conducting mass remained unchanged , the distribution of the magnetization of its substance might be altered . Before the magnetic force was applied , a great effect on the neutral point of the multiplying branch was observed , taking place gradually during several minutes , and obviously due , in a great measure , to variation of the distribution of temperature in the conducting square . ( See below , S 177 , for an illustration of this effect . ) When a new neutral point was found , the magnet was made , reversed , unmade , & c , and always with the same effects as before . Different arrangements of the little masses of soft iron produced different absolute effects on the neutral point , causing it to shift sometimes as much as fifteen inches on the multiplying branch , but the effects of magnetism were invariably found to be consistent with the first-mentioned result . As the distribution of the magnetism in the square plate must have varied very much under these different circumstances , and in all probability must have been in some of the cases more intense in the quarters towards AE and CB than in those towards AC and DB , the conclusion could scarcely be avoided , that the conductivity of the magnetized substance was greater across than along the lines of magnetization . For the purpose of further testing and illustrating this conclusion I planned the following experiment , to compare directly the resistances of two equal and similar squares of sheet iron , equally and similarly magnetized , arranged in the same circuit to conduct electricity across the lines of magnetization of one and along those of the other . 167 . Exp. 5 . To compare the conductivities of magnetized iron along and across the lines of magnetization . A piece of sheet copper , BCHK ( fig. 48 ) , 3 inches long , 2 broad and ^ inch thick , was bent round the line FH into the form shown in fig. 49 . Fig. 48 . Fig. 49 . Fig. 50 . A square of thin sheet iron , 2 inches wide ( weighing 103 grains ) , was soldered by one side to the edge CH of the copper in the position shown in fig. 50 . The projecting part , FBKL , of the copper slip was bent round its middle line EG , so as to bring its edge , BK , close over the edge of the iron square lying over FC ; and to this edge , BK , in its new position ( fig. 51 ) , a second iron square , of the same dimensions and weight as the other , was soldered by one side , with its area lying in a position close to that of the former . The relative position of the two squares and the connecting piece of copper will be understood by looking at fig. 52 , which represents the Fig. 51 . Fig. 52 . iron squares as if soldered to the piece of copper before it was bent , and the iron square CDMH turned round its side CH , from the position close to the plane of the copper adjoining it , into a position in this plane continued across CH . If , now , we suppose the iron square CDMH to be turned down so as to lie below a square , FL'HC , of the copper ; this square of the copper to be bent sharp round its diagonal , FH , till the part FL'H lies over HCF ; and , lastly , the part FL/ KB projecting beyond FC to be bent downwards round EG with a less sharp bend ; the iron square , ABKL , will be brought close under the other one , CDMH , with the edges of the two which are connected to the edges of the copper perpendicular to one another , and the whole compound conductor will have exactly the position shown below in fig. 54 . 168 . A convenient electrode was soldered along the edge of each iron square parallel to the edge of the same square soldered to the connecting piece of copper ; so that a powerful electric current entering by one of those electrodes and carried away by the other would pass through the second-mentioned square of iron in lines exactly parallel to the side AB , through the connecting piece of copper in lines which were parallel to its length , BC , before it was bent ; and through the first-mentioned square in lines exactly parallel to its side CD , and therefore perpendicular to the lines along which it traverses the second square . The course of the current will be understood by looking at fig. 52 , where the two squares and the copper connecting them are supposed to be opened out so as to throw the course of the current into a straight line . The order followed in constructing the compound conductor was not exactly the order of the description given above ; but the connecting piece of copper was first cut and bent , and other pieces , to serve as electrodes ( shown in the accompanying views , fig. 52 ) , were prepared , and the iron squares , put in their proper places , were then soldered by their edges to the edges of the connecting piece , and the electrodes Fig. 53 . were soldered to their opposite edges . A view of the whole thus put together , with the reference and testing wires described below , is given in fig. 54 . A testing conFig . 54 . ductor of two yards of No. 18 copper wire was soldered , with its two extremities to the copper electrodes , close to the middle points of the edges AL , DM of the iron squares ; and a fixed galvanometer electrode was soldered to the middle point , N , of the copper connecting piece . 169 . The squares , their electrodes , the connecting piece , and the testing conductor

41206196

2610523

On the Construction of the New Imperial Standard Pound, and its Copies of Platinum; and on the Comparison of the Imperial Standard Pound with the Kilogramme des Archives

753

946

Philosophical Transactions of the Royal Society of London

W. H. Miller

fla

6.0.4

transactions

http://corpora.clarin-d.uni-saarland.de/surprisal/6.0.3/?id=41206196

http://www.jstor.org/stable/41206196

Measurement

Chemistry 1

Measurement

On the Construction of the New Imperial Standard Pound , and its Copies of Platinum ; and on the Comparison of the Imperial Standard Pound with the Kilogramme des Archives . By W. H. Miller , M.J. , F.R.S. , Professor of Mineralogy in the University of Cambridge . Received up to p. 895 April 16 , -Read April 24 , 1856 ; from p. 895 Received June 7 , Read June 12 , 1856 . History of the Standards of English Weight . Y HE earliest legal standard of English weight , of which any very authentic account is preserved , is the weight called the pound of the Tower of London . According to Folks * , it was the old pound of the Saxon Moneyers before the Conquest . This pound was lighter than the troy pound by three-quarters of an ounce troy , and did not very sensibly differ from twelve ounces of the weight still used in the money affairs of Germany , and there known by the name of the Cologne weight . It is most probable that the pound of the Tower of standard silver was then cut up into 240 pennies ; whence the weight of the penny will be 225 troy grains . The silver pennies of the first two kings after the Conquest agree , as near as can be judged , in weight and goodness , with the pennies of the Sajcon kings their immediate predecessors . It is therefore reasonable to think that King William introduced no new weight into his Mints . Clarke , in his Treatise on the connexion of Roman , Saxon and English Coins , p. 97 , considers this evident from the words of William I. : ' Statuimus et pr\#339 ; cipimus , quod habeant per Universum regnum mensuras fidelissimas , et signatas ; et pondera fidelissima , et signata , sicut boni prsedecessores nostri statuerunt . ' And also ( p. 152 ) from one of the Conqueror 's laws , where it is said , that the Saxon shilling was four pence ( from the time of Athelstane ) , the preamble of which informs us , that these laws were in force during the Confessor 's reign : 'Ice les meismes , que le Reis Edward sun Cousin tint devant lui . ' That the Tower pound was lighter than the troy pound by three-quarters of an ounce troy , appears by a verdict relating to the coinage dated 30th October , 1527 , 18 Hen . VIII . , in the Exchequer , in which are the following words : c And whereas heretofore the merchant paid for coinage of every pound Towre of fine gold , weighing xi oz. quarter Troye , ii s. vi d. Now it is determined by the King 's highness , and his said councelle , that the foresaid pound Towre shall be no more xMILLER ON THE CONSTRUCTION OF THE NEW STANDARD POUND . used and occupied , but al manner of gold and sylver shall be weighed by the pound Troye , which makes xii oz. Troye , which excedith the pound Towre in weight iii quarters of the oz. ' Hence it follows that the weight of the Tower pound was 5400 troy grains , and that of the ounce or the twelfth part thereof 450 like grains . He quotes a passage taken from the Register of Accounts in Paris , to prove that the Tower pound was also known in France , where it was called the Rochelle or English weight . The difference of the several pounds then made use of in France is there computed , and the proportion between the troy and English weights is thus estimated : ' Ou royaume souloit avoir iv marcs : c'est assavoir le marc de Troyes , qui poise xiv sols , ii den . Esterlins de poix le marc de la Rochelle , dit d'Angleterre , qui poise xiii s. iv den . Esterlins de poix . ' It is supposed that this account was taken about the beginning of the reign of Edward HI . , not long after 1329* . Since the sol=12 esterlings , the ratio of the standards of Troyes and Rochelle is as 17 to 16 ; whence , supposing the weight of Troyes to be the same as the English troy weight , the Rochelle ounce =45176 troy grains . He refers to a statute of the 51st of Henry III . , called ' Assisa panis et cerevisiae , ' to show that the weights in use at that time , though commonly taken to have been troy weights , were not really so , but the money weights : 'By consent of the whole realm of England the king 's measure was made , that is to say that an English penny , which is called a sterling , round without clipping , shall weigh xxxii grains of wheat dry in the middest of the ear ; and xx pence make an ounce , and xii ounces make a pound . ' For otherwise the pennyweight here described , could never be , as the statute plainly implies , the true weight of the English coined penny . Folks determined the weights of a number of silver coins well preserved , or but little impaired , in troy grains ( p. 159 ) . Five pennies of Henry III . weighed 22*5 grains each , and one 22*25 grains . Of four pennies of Edward I. , two weighed 22*5 grains each , and two others 22 grains each . Assuming the true weight of the penny at this time to be 22*5 grains , which was also that of the Saxon penny^ , the weight of the pound will be 5400 grains . It is , however , just possible that the weights were adjusted in conformity with the words of the Act , but that the coin called the sterling fell 1-5 grain short of the full weight of 32 corns of wheat , or 24 grains troy , the weight of 4 corns of wheat being usually considered equivalent to 3 grains troy . On this supposition the pound defined in the statute of the 51st of Henry III . , and in the 31st of Edward I. , in precisely the same words , would be the pound of 5760 troy grains . That another pound , the libra mercatoria , was in use at this time , is shown by the following extract from the Treatise on Arithmetic , by Dr. Peacock , in the Encyclopaedia Metropolitana , Art . 166 : ' Though this weight was the favourite of the legislature , there was another pound , one-fourth greater , which was in more general * Clarke , p. 15 . f Ibid. p. 428 . use ; it is mentioned in a Tractatus de Ponderibus of the same age ( the time of Edward I. ) , where the two pounds are said to consist of 20 and 25 shillings respectively : in the statute of the 54th of Henry III . , where the composition of the gallon and pound ( troy ? ) are given , there is mentioned also una libra , pondus vigintiquinque solidorum legali urn sterlingorum . On many other occasions this libra mercatoria is referred to , and we may consider its use in mercantile transactions and ordinary sales as nearly universal . ' If the pound mentioned in the 51st and 54th of Henry III . , and the 31st of Edward I. , be supposed to contain 5400 grains troy , the libra mercatoria will contain 6750 grains , which does not differ very much from the old pounds of Villefranche ( 6741*9 grains ) , Zieriksee ( 6736 grains ) , Dresden stahlgewicht ( 6726*2 grains ) , Dantzig ( 6722 grains ) , Embrun ( 6714 grains ) , Murcia ( 6711 grains ) . This supposition is rendered probable by a passage from Fleta quoted by Clarke , p. 96 , who says , ' Quindecim unciae faciunt libram mercatoriam . ' Fifteen Tower ounces of 450 troy grains , twelve of which make the Tower pound , are equal to 6750 troy grains . Sixteen of these ounces make 7200 troy grains , a weight which approaches very closely to the^ Ptolemaic mina of 7199*96 troy grains , the 100th part of the large Alexandrian talent , also divided into 16 ounces . This weight appears to have survived in the old pounds of Namur ( 7201*1 grains ) , Altenburg ( 7202 grains ) , Ciney ( 7202*5 grains ) , Valenciennes ( 7195*2 grains ) , Duerstadt ( 7206*1 grains ) , Wittenberg ( 7207 grains ) , Heidelberg ( 7207*22 grains ) , Ai* la Chapelle ( 7208 grains ) , Liege ( 7209*1 grains ) , Bruchsal ( 7190 grains ) , Brunswick ( 7212*3 grains ) , Mons ( 7185-2 grains ) , Dresden ( 7215*4 grains ) , Binche ( 7185 grains ) , Gotha ( 7213*85 grains ) , Jemappe ( 7185*2 grains ) , in the well-known Cologne pound of 7216 grains , and in many others differing rather more largely from 7200 grains . If , on the other hand , the pound of Henry III . and Edward I. contained 5760 troy grains , the libra mercatoria would weigh 7200 troy grains . In the Acts of the 2nd of Henry V. st. 2 . c. 4 , and of the 2nd of Henry VI . c. 13 , relating to Goldsmiths , mention is made of the 'Pound Troy* . ' Either the Tower pound was abolished , or the use of the troy pound as a legal standard confirmed in 1498 , the 12th of Henry VII . A statute made in that year enacts 'That every gallon contain viii li of wheat of Troy weight and every pound xii ounces of Troy weight , and every ounce contain xx sterlings . ' The sterling here mentioned must have been a weight , and not the coin of that name ; for , during the reign of Henry VII . , the weight of the groat was 48 grains , and that of the shilling 144 grains , which gives only 12 grains for the weight of the coin called the penny or sterling-f ' The troy pound appears to have been derived from the Roman weight of 5759*2 grains , the 125th part of the large Alexandrian talent , and which , like the troy * Reynardson , Philosophical Transactions , vol. xlvi . p. 61 . f Folks , p. 16 . pound , was divided by the Romans into 12 ounces . So also the avoirdupois pound was probably derived from the large Attic mina of 6945*3 grains troy , the 60th part of the large Attic talent , divided by the Romans , as the pound avoirdupois is divided , into 16 ounces , of nearly the same weight as the modern Roman ounce * . According to Greaves , it approximates much more closely to the ancient Roman ounce . The word ' avoirdepois , ' applied to commodities , occurs in statutes of the 9th and 27th of Edward III . By a statute of the 24th of Henry VIIL , butchers were obliged to provide themselves with beams , scales and weights sealed , called ' haberdepois . ' It is not known when the avoirdupois weight was first introduced . Two weights , one of which , in its present state , is about 650 grains less than seven pounds avoirdupois , in the possession of C. C. Babington , Esq. , of St. John 's College , Cambridge , are marked with a crowned H , which is supposed to be of the time of Henry VII . Two weights , one of 2 pounds , the other of 4 pounds avoirdupois , ornamented with the Tudor rose , and marked with the letter H , and therefore probably of the reign of either Henry VII . or Henry VIIL , are preserved in the University Library , Cambridge . In the reign of Elizabeth avoirdupois weights were deposited in the Exchequer , as appears from the name and inscription thereon . The Transactions of the Royal Society , for 1742 and 1743 ( vol. xlii . p. 541 ) , contain an account of the comparison of various standards of measure and weight , from which the following extracts are made : ' The weights in His Majesty 's Exchequer , and which are esteemed the standards , are a pile , or box , of hollow brass weights , from 256 ounces ( troy ) downwards , to the 16th part of an ounce , all severally marked with a crowned E. ' ' The weight mentioned in all our old Acts of Parliament , from the time of King Edward L , is universally allowed to be the troy weight , whose pound consisted of 12 ounces , each of which contained 20 pennyweights . And as the pound is the weight of the largest single denomination commonly mentioned in those Acts , 12 ounces taken from the pile of troy weights above mentioned , as there is no single troy pound weight , must now be reputed to be the true standard of the troy pound , used at this day in England . 6 Besides which troy standards , there are also kept in the Exchequer the following standards for averdupois weights ; that is to say , a fourteen pound bell-weight of brass , marked with a crowned E , and inscribed XIIII . POVNDE AVERDEPOIZ . ELIZABETH . REGINA . 1582 . As also a seven pound , a four pound , a two pound , and a single pound , like averdupois bell-weights , and severally marked as follows , excepting the variations for the number of pounds in each respective weight . ' ( The marks are : VII . A. , AN0 DO , a crowned E. L. , 1588 , A0 REG . XXX . ) With which are also kept a pile of flat averdupois weights , from 14 pounds to the 64th part of a pound . ' The comparisons were made with considerable care , the weights being interchanged so as to eliminate the error produced by the inequality of the arms of the balance . The results , in ounces troy , and grains of which the ounce contains 480 , are 14 lb. +l lb. ( bell-weights)=218 oz. 335-25 grains== 104975-25 grains . 7 lb. ( bell-weight ) = 102 oz. 45 grains=49005 grains . 1 lb. ( bell-weight ) = 14 oz. 282 grains= 7002 grains . 1 lb. ( flat weight ) =1 lb. ( bell-weight ) 2*5 grains=6999*5 grains . In the year 1758 , a Committee of the House of Commons , appointed to inquire into the standards of weight and measure , recommended that the troy pound should be made the unit or standard by which the avoirdupois and other weights should be regulated . By order of the Committee , three several troy pounds were adjusted with great care , under the direction of Mr. Harris , the then Assay Master of the Mint , by a mean of a great number of comparisons with the old weights in the Exchequer . The details of the comparisons are given at length in the Report of the Committee , presented by Lord Carysfort on the 26th of May , 1758 . One of these weights ( the imperial standard troy pound which was destroyed by the burning of the Houses of Parliament in 1834 ) was placed in the custody of the Clerk of the House of Commons . The bill , however , brought in by Lord Carysfort in 1760 to give effect to the recommendations of the Committee , in the pressure of business attending the death of George II . and the accession of George III . , and the dissolution of Parliament soon following , was not carried through all its stages . In the year 1818 , Sir Joseph Banks , Sir George Clerk , Mr. D avies Gilbert , Dr. W. H , Wollaston , Dr. Thomas Young , and Captain Kater , were appointed Commissioners for considering how far it might be practicable to establish a more uniform system of weights and measures . In that part of their Report which relates to the subject of Weights , they recommend that the Parliamentary standard of 1758 should remain unaltered : they state that the avoirdupois pound , which has long been in general use , though not established by any act of the Legislature , is so nearly 7000 troy grains , that they recommend that 7000 such troy grains be declared to constitute a pound avoirdupois : also , that from Sir George Shuckburgh 's weighings of a cube , cylinder and sphere in air and in water in 1797 ? and Captain Kater 's measurements of the linear dimensions of the same in 1821 , they determined the weight of a cubic inch of distilled water , weighed in air by brass weights , at the temperature of 62 ' Fahr. , the barometer being at 30 inches , to be equal to 252-458 grains , of which the Imperial standard troy pound contains 5760 . The chief recommendations of this Committee passed into law by an Act of Par5 g 2 liament on the 17th of June , 1824 . In the fourth clause of this Act it is enacted , that the old troy pound of 1758 , now in the custody of the Clerk of the House of Commons , shall continue to be the original unit or only standard of weight from which all other weights shall be derived ; and that it is to be denominated The Imperial Standard Troy Pound ; ' and that the avoirdupois pound , now in use , shall contain 7000 grains , of which the troy pound contains 5760 . In the sixth clause it is enacted , that if the standard troy pound should be lost or destroyed , it is to be restored by a reference to the weight of a cubic inch of distilled water , which has been found and is declared to be 252*458 troy grains , weighed in air with brass weights , at the temperature of 62 ' Fahr. , the barometer being at 30 inches . The Imperial standard troy pound was compared with five troy pounds of gunmetal , destined for the use of the Exchequer , the Royal Mint , and the cities of London , Edinburgh and Dublin , by Captain Kater in 1824 or 1825 * . Denoting the standard troy pound by U , and the troy pounds of the Exchequer , the cities of London , Edinburgh , Dublin , and the Royal Mint , by Ex , L , Ed , D , RM respectively , it was found that No. of Comps . grain . 16 Ex =U + 0-0010 12 L =U+0-0005 15 Ed = U-0-0015 18 D =U + 0-0022 20 RM=U+0-0021 In the year 1829 the standard troy pound was compared with extraordinary care by Captain v. Nehus with two brass troy pounds and a platinum troy pound , all in the custody of Professor Schumacher , and with a platinum troy pound , the property of the Royal Society . Let Sb , K denote the two brass troy pounds , Sp the platinum troy pound in the custody of Professor Schumacher , RS the platinum troy pound the property of the Royal Society , t the temperature of the air in degrees of Fahrenheit 's scale , b the height of the mercury in the barometer in English inches , and reduced to the temperature of melting snow . Let A prefixed to the symbol of any weight denote the ratio of the density of the weight at the temperature of melting snow to the maximum density of water . The symbol a placed between the symbols of two weights will be used to denote that they appear to be equal when weighed in air . The two weights in this case will not be equal unless their volumes are equal . When the weighings have been made in air of constant density , or have been reduced to what they would have been in air of given density ; or when , the volumes of the weights and the temperature and pressure of the air being unknown , we are compelled to assume the equality of their volumes , the symbol = may be substituted for a. According to the observations of Captain v. Nehus , No. of Comps . gr. b. t. 300 Sp ^U-0-00857 29-722 65-62 140 RS ^U-0-00205 29*806 65-73 60 Sb ^U-0-01034 29*965 64-50 92 K\#163 ; tU + 0-03389 29*646 65-09 16 RM : Q:U + 0-00887 29*679 65-91 10-logASp=8-67392 , 10-log ARS=8-67392 , 10-log ASb=9'08471 , 10 -log AK= 9*09724* . In the burning of the Houses of Parliament in 1834 , all the standards of measure and weight were either totally destroyed , or injured to such an extent as to render them quite useless as standards . The Imperial standard troy pound was never recovered from the ruins . In the year 1838 , the Astronomer Royal , Mr. F. Bailey , Mr. J. E. D. Bethune , Mr. Davies Gilbert , Sir J. F. W. Herschel , Mr. J. S. Lefevre , Mr. J. W. Lubbock , the Rev. George Peacock , and the Rev. R. Sheepshanks , were appointed Commissioners to consider the steps to be taken for the restoration of the standards of weight and measure , to replace those which were destroyed by the burning of the Houses of Parliament . They found provisions for the restoration of the lost standards prescribed to them by Sections 3 and 5 of the Act 5th George IV . , whereby it is directed that , in case of the loss of the standards , the yard shall be restored by taking the length which shall bear a certain proportion to the length of the pendulum , vibrating seconds of mean time in the latitude of London , in a vacuum , at the level of the sea ; and that the pound shall be restored by taking the weight which bears a certain proportion to the weight of a cubic inch of water weighed in a certain manner . The Commissioners , however , in their Report , dated December 21 , 1841 , decline to recommend the adoption of these provisions for the following reasons : ' Since the passing of the said Act , it has been ascertained that several elements of reduction of the pendulum experiments therein referred to are doubtful or erroneous It is evident , therefore , that the course prescribed by the Act would not necessarily reproduce the length of the original yard . It appears also that the determination of the weight of a cubic inch of water is yet doubtful ( the greatest difference between the best English , French , Austrian , Swedish and Russian determinations being about -reo^ 'f the whole weight , whereas the mere operation of weighing may be performed to the accuracy 'f 1,000,000 'f the whole weight ) . Several measures , however , exist , which were most carefully compared with the former standard yard ; and several metallic weights exist , which were most accurately compared with the former standard pound ; and by the use of these , the values of the original standards can be respectively restored without sensible error . And we are fully persuaded that , with reasonable precautions , it will always be possible to provide for the accurate restoration of standards by means * Schumacher , Philosophical Transactions for 1836 , p. 437 . of material copies which have been carefully compared with them , more securely than by reference to experiments referring to natural constants . ' The weight of a given volume of water at 62 ' Fahr. , by mea*is of which the Act of Geo. IV . directs the pound to be restored , was deduced from the weighings in air and in water of a brass cube of 5 inches , of a cylinder of 4 inches diameter and 6 inches long , and of a sphere of 6 inches diameter , by Sir George Shuckburgh in 1797* and the measurements of their linear dimensions by Captain Kater in 1821 . The resulting values of the weight of a cubic inch of water at 62 ' Fahr , in vacuum , in grains of which the lost standard pound contained 5760 , were , by the cube 252*741 , by the cylinder 252*685 , by the sphere 252741 . Mean 252*722* . Similar observations had been made in France by MM . Lefevre-Gineau and Fabbroni for the purpose of establishing the value of the kilogramme , which was intended to be the weight of a cubic decimetre of water at its maximum density , in a vacuum : the solid used on this occasion was a cylinder the diameter and axis of which were nearly 243*5 millimetres each-f- . In Sweden , MM . Berzelius , Svanberg and Akermann , who employed a cylinder 4 inches in diameter and 6 inches long , found the weight of a cubic decimetre of water , at 62 ' Fahr , in a vacuum , to be 2*350595 Swedish pounds J. In Austria , Professor Stampfer , who used a cylinder of about 3*11 inches diameter and 3*11 inches long , found the weight of a Vienna cubic inch of water , at 62 ' Fahr. in a vacuum , equal to 18*2492 grammes S. Lastly , in Russia , Professor Kupffer has determined the weight of an English cubic inch of water in vacuum at 62 ' Fahr. , in doli of which a kilogramme contains 22504*86 , to be 368*380 by a cylinder the axis and diameter of which were nearly 80 millimetres each , and 368*341 by a cylinder the axis and diameter of which were 4 English inches each . Mean 368*361 doli . At the end of the work entitled c Travaux de la Commission pour fixer les Mesures et les Poids de l'Empire de Russie , ' Professor Kupffer has collected the different results expressed in doli . The English observations are affected by a small error arising from the uncertainty of the value of Professor Schumacher 's troy pound K , which was used by Professor Kupffer in finding the relation between the English and French standards of weight . This error , however , is quite insignificant compared with the differences between the results obtained by the several observers . French observations 368*365 English observations 368*542 Swedish observations 368*474 Austrian observations 368*237 Russian observations 368*361 * Philosophical Transactions for 1821 , Part I. p. 326 . t Base du Systeme Metrique , t. iii . p. 558 . I Memoirs of the Royal Academy of Stockholm , 1825 . S Jahrbucher des k. k. Polytech . Institutes zu Wien , B. 16 , S. 53 . Assuming the Russian observations to be the most accurate , as they probably are , it will be seen that even if we leave entirely out of the question the injurious effect of the error likely to arise in establishing the standard of length , a troy pound deduced according to the method prescribed by the Act would be 2*829 grains too heavy ; while , if the Austrian observations had been accepted as the best , the troy pound would have been 4707 grains too heavy . On the other hand , it was possible to recover the weight of the lost standard in air to within a fraction of O'OOl grain , by means of the troy pounds which had been compared with it , and could be easily brought together for recomparison . Seeing , then , that the error of one of these two methods of restoring the lost standard is at least 2829 times as large as the error of the other method , the Committee could not hesitate to recommend the adoption of the latter . The Commissioners recommend also that the avoirdupois pound , being universally used through the kingdom , while the troy pound is wholly unknown to the great mass of the population , be adopted as the standard of weight ; that the troy pound be no longer recognized ; and that the use of the troy ounce be confined to gold , silver , and precious stones . In the year 1843 a Committee was appointed to superintend the construction of the new Parliamentary standards of length and weight , to replace those which were destroyed by the burning of the Houses of Parliament . The members of this Committee were , the Astronomer Royal , the Marquis of Northampton , the Earl of Rosse , the Lord Wrottesley , Sir J. W. Lubbock , Bart. , Sir J. F. W. Herschel , Bart. , the Rev. G. Peacock , Dean of Ely , the Rev. R. Sheepshanks , F. Bailey , Esq. , J. E. D. Bethune , Esq. , J. G. S. Lefevre , Esq. , and Professor W. H. Miller . To the last of these was entrusted the construction of the new standards of weight . The evidence for ascertaining the weight of the lost Standard Troy Pound , placed at the service of this Committee , consisted of the following weights : The brass troy pound of the Exchequer Office . The brass troy pounds from the cities of London , Edinburgh and Dublin . The platinum troy pound and the two brass troy pounds then in the custody of Professor Schumacher . The platinum troy pound of the Royal Society . The troy pound used by the late Mr. Robinson of Devonshire Street , Portland Place , purchased by the Committee . Two troy pounds , formerly in the possession of Mr. Bingley ( one of which , lately in the possession of Stansby Alchorne , Esq. , of the Royal Mint , has been purchased by the Committee ) . The troy pound formerly the property of Mr. Freeman , now the property of Messrs. Vandome and Titford . To these has very recently been added a troy pound the property of the Bank of England . The results of the comparisons of the troy pounds of the Exchequer Office , of the cities of London , Edinburgh and Dublin , and of the three troy pounds in the custody of Professor Schumacher , and the troy pound of the Royal Society , with the lost standard , have already been given . Mr. Robinson 's troy pound is also said to have been compared by Captain Kater , but no record has been discovered of the comparison . Mr. Vandome 's pound , Mr. Bingley 's troy pounds , and the Bank of England troy pound , were all constructed , along with the lost standard , in 1758 by Mr. Harris , Assay Master of the Mint . These were referred to , at the suggestion of Professor Schumacher , in the hope of arriving at a knowledge of the volume of the lost standard , which unfortunately had never been determined by weighing it in water . For , as long as the volume of the lost standard remains unknown , the weight of the air displaced by it , and , consequently , its absolute weight , is uncertain within limits far exceeding the errors of weighing . The first step in the process of arriving at the weight of the lost standard , was obviously to compare among themselves the different troy pounds with which the lost standard had been compared by Captain Kater and Captain v. Nehus . These comparisons were made with a balance of extreme delicacy procured from Mr. Barrow . In its construction it nearly resembles the balances of the late Mr. T. C. Robinson . The beam is made sufficiently strong to carry a kilogramme in each pan . The middle knife-edge is about T93 inch long , and rests , when the balance is in action , throughout its whole length on a single plane surface of quartz . The surfaces of quartz which rest upon the extreme knife-edges , and from which the pans are suspended , are also plane . The distance between the extreme knife-edges is about 15*06 inches , the length of each about l'O5 inch . Instead of having an index pointing downwards , as is usual in balances of this description , the beam has a pointer at each end , and a graduated scale is carried by an arm attached to the pillar of the balance at a little distance behind the left-hand pointer . Affixed to the right-hand end of the beam is a thin slip of ivory , a little more than half an inch long , divided into spaces of about 0*01 inch each , or subtending an angle of about 5 ' each at the middle knife-edge . This scale is viewed through a compound microscope , having a single horizontal wire in the focus of the eye-piece . The distance between two divisions of the scale , as seen through the microscope , subtends an angle of about 37 ' . This contrivance for determining the position of the beam at the extremity of an oscillation , was found so superior to a scale and pointer viewed with the naked eye , that after a trial of a few days , the scale at the left hand was found to be a useless encumbrance and was accordingly removed . A screen was interposed between the observer and the front of the balance case , having a small opening opposite to the eye-piece of the microscope , through which the scale could be seen . In order to admit of the employment of a large vessel of water in observations for finding specific gravities , the base of the balance has an opening immediately under the right-hand pan , capable of being closed when not in use by a sliding plate of brass . A corresponding opening exists in the table on which the balance stands . The vessel of water is placed under the table , and the wire by which the object to be weighed in water is suspended from a hook under the right-hand pan , passes through the openings in the base of the balance under the table . In the comparisons of weights , I at first employed the method of weighing invented by the Pere Amiot , more commonly known as Borda's* . The counterpoise was invariably placed in the left-hand pan , and the weights to be compared alternately in the right-hand pan . The reading of the divided scale was noted at the end of each of three consecutive oscillations . One-fourth of ( first reading+ third reading+2 second reading ) was taken as the reading of the scale in the position of equilibrium of the balance . In all the more important weighings the reading of the scale was noted at the end of each of four consecutive oscillations , of which the last three only were used in finding the reading corresponding to the position of equilibrium of the beam . The first reading is apt to exhibit small irregularities , especially when it follows very soon after the interchange of the weights . Hence the employment of it in finding the position of equilibrium would not be likely to increase the accuracy of the result . The observation of an additional reading is not , however , without its use ; for by comparing the first with the third , as well as the second with the fourth , the error of an integer in either of the readings , if it occurred , would be instantly detected . Let P , Q be the apparent weights in air of two bodies P , Q , either of which in the right-hand pan is nearly in equilibrium with the counterpoise C in the left-hand pan ; ( C , P ) , ( C , Q ) the scale readings in the position of equilibrium of the balance when P , Q respectively are in the right-hand pan ; and let m be the weight equivalent to one part of the scale , the readings increasing with an increase of the weight in the right-hand pan . Then Q=P+m[(C , Q ) ( C , P ) ] . Subsequently I used the method attributed to Gauss-^ . Let P , Q be the apparent weights in air of two bodies P , Q , and ( P , Q ) the reading of the scale in the position of equilibrium of the balance , when P is in the left-hand pan , and Q is in the righthand pan . Now let P be placed in the right-hand pan , and Q in the left-hand pan , and let P , Q become R , S respectively , by the addition of small weights , in order to bring the balance nearly into its former position of equilibrium . Let ( S , R ) be the reading of the scale in the position of equilibrium of the balance , when R is in the righthand pan , and S is in the left-hand pan . Then , m being the weight equivalent to one division of the scale , the reading increasing with an increase of weight in the righthand pan , Q+S=P+R+ra[(P , Q)-(S , R ) ] . When the weights P , Q are very nearly equal , the balance may be so adjusted by placing a small constant weight in one of the pans or hanging it on the beam , that , on interchanging the weights P , Q , the position of equilibrium may still be near the middle of the scale . Supposing the balance to be so adjusted , let ( P , Q ) be the reading of the scale in the position of equilibrium of the balance , when P is in the lefthand pan and Q is in the right-hand pan ; and let ( Q , P ) be the reading of the scale * Peclet , Course de Physique , p. 48 . when the balance is in its position of equilibrium , with Q in the left-hand pan and P in the right-hand pan . Then 2Q=2P+w[(P , Q ) ( Q , P ) ] . In making a large number of comparisons , the weights are exposed to the risk of being injured by wear . In order to obviate this danger , two light pans were pro\#171 ; cured of very nearly equal weight , each of which has a loop of wire forming an arch the ends of which are attached to the pan at opposite extremities of a diameter of the pan , by which the pan could be lifted with the hook at the end of a long handle , into or out of either of the pans of the balance . Calling the pans X and Y , and the weights to be compared P and Q , P was placed in X and Q in Y , and P+X compared with Q+Y n times ; then P was placed in Y and Q in X , and P+Y compared with Q+X n times . The weights were thus exposed to the wear of two ordinary comparisons only in the course of 2n comparisons . The mean of the 2n comparisons gives the difference between P and Q , unaffected by the very small but unknown difference between the weights of the pans X and Y. This contrivance was found to be especially useful when either of the weights to be compared consisted of several parts . An improvement upon this was made by using the pans of one of the balances employed by the French Pharmaciens , which resemble those above described , with the addition of an iron hook at the highest point of the wire loop . Either pan is suspended by a wire of suitable length bent into a hook at each end , from the ring attached to the agate-plane . In using the method of double weighing , the original left-hand pan of the balance was suffered to remain with the counterpoise in it , and the pan X containing the weight P , and the pan Y containing the weight Q , alternately suspended from the right-hand end of the beam , and the positions of equilibrium observed ( usually about twenty times ) . The weights were then interchanged , and pan Y containing the weight P , and pan X containing the weight Q , suspended from the right-hand eiid of the beam , and the positions of equilibrium observed the same number of times . The weights of X and Y were frequently reduced in order to make them as nearly equal as possible , and sometimes in order to remove rust from the iron hooks . In using Gauss 's method , it was desirable to be able to transfer the pans , and the weights contained in them , from one end of the beam to the other without opening the doors of the balance-case , and thus avoid sudden changes of temperature of air within the balance-case , and consequent production of currents of air . In order to effect this , various contrivances were tried . Of these the following proved the most successful . A slender brass tube , 38 inches long , passes freely through two holes in the ends of the balance-case , which is 22*75 inches long , near the top of the case , and half-way between the balance and the front of the case . To the middle of the tube is attached a descending loop of wire . Suppose that by sliding the rod , the loop is brought near to the right-hand end of the beam , and a pan with a weight in it transferred from the end of the beam to the wire loop by a brass rod having a deep groove filed round it near the end , which is inserted through a hole in the middle of the right-hand end of the balance-case . By sliding the rod in the opposite direction , the loop with the pan and weight suspended from it , is brought near to the left-hand end of the beam , . to which the pan is transferred by a brass rod passing through a hole in the left-hand end of the balance -case . Pins inserted in holes at each end of the tube at right angles to it , prevent it from being pushed too far . A similar tube half-way between the balance and the back of the case , serves to transfer the other pan and weight from one end of the beam to the other . In this manner any number of comparisons may be made without opening the balance-case , except in the middle of the series , for the purpose of changing the pans . The transfer of the pans and weights from one end of the beam to the other , might be effected still more conveniently by means of two coarse screws of the same length as the balance-case , turned by small winches at each end , and provided with loosely-fitting nuts with wire loops from which to suspend the pans and weights . In the course of making the preliminary observations some peculiarities of the instrument were discovered , which , though they probably exist in other balances , do not appear to have been hitherto noticed . One of these is , that the expansion of one arm by heat , the left in the present case , is a little greater than that of the other arm . Hence , when the weights in the two pans are nearly equal and of equal volume , the reading of the scale in the position of equilibrium diminishes as the temperature of the beam increases . Another is , that the sensibility of the balance , as measured by the number of parts of the scale equivalent to a given weight , was found to diminish with an increase of temperature . The cause of this is obvious . The beam being of bronze and the knife-edges of steel , the balance-beam becomes an over-compensated pendulum , and an increase of temperature increases the distance between the middle knife-edge and the centre of gravity of the beam and weights , supposing the latter concentrated in the extreme knife-edges . Possibly also , the flexure of the beam may increase with the temperature , or the mean expansion of the upper bar of the beam may be greater than that of the under bar . The variation of the sensibility of the balance is so large , that it is necessary to determine the weight equivalent to a given number of parts of the scale for each set of observations , except in cases where the temperature is very nearly the same . For the comparison of the smaller weights two excellent balances by Robinson were used , one having a beam 10*5 , the other a beam 5*5 inches long . The reading of the scale of these balances increases on the addition of a small weight to the weight in the left-hand pan . Comparisons of Sp , RS , Sb , K , Ex , L , Ed , R. T is a platinum troy pound left a little in excess ; P the sum of five weights of platinum making together a troy pound ; b is the height of the mercury in the 5h 2 Sp , RS , K , ETC . 769 Whence V+p ! p appears to weigh as much as Q+ ? 'q in air ( thermometer =* ' , barometer = bf ) . In calculating the densities of Sp , K , Sb , Professor Schumacher adopted the formulae and constants given in Bessel 's paper on the reduction of weighings , in the Astronomische Nachrichten , B. vii . S. 373 . It will therefore be proper to use his tables in reducing the weighings of 1844 , even though the values of some of the constants , according to recent and more accurate observations , differ slightly from those employed by Bessel . Let up be the volume of the weight P at the temperature of melting snow , the unit of volume being the volume of one grain of water at its maximum density ; p the weight in grains of the air displaced by P ; t the temperature of the air in degrees of Fahrenheit 's scale ; and b the height of the mercury in the barometer in English inches reduced to the temperature of melting snow . Then log p= log b+ log w + log from Table A. + log from Table B. or P. , according as the weight is of brass or platinum , t being the argument in each of the tables . Of the following tables , copied as far as they are wanted from the Philosophical Transactions for 1836 , p. 486 , A contains the logarithm of the ratio of the density of air temperature t , and under the pressure of one inch of mercury at the temperature of melting snow , to the maximum density of water . B and P contain the logarithms of the ratio of the density of brass and platinum , respectively , at the temperature of melting snow , to the density at the temperature t of Fahrenheit 's scale . t. a. t. b. u p. 61 5-61177 61 0-000394 61 0-000189 62 5-61092 62 0-000408 62 0-000195 63 5-61007 63 0-000421 63 0-000202 64 5-60922 64 0-000435 64 0-000209 65 5-60837 65 0-000449 65 0*000215 66 5-60752 66 0-000462 66 0-000222 67 5-60668 67 0-000476 67 0-000228 Let A prefixed to the symbol by which any weight is designated denote the ratio of the density of the weight at the temperature of inelting ice to the maximum density of water . Then ( Philosophical Transactions for 1836 , pp. 490-493 ) , ASp=21*1874 , ARS=21*1874 , AK=7*994 , ASb=8*228 . The density of U is unknown . Let it be assumed equal to a mean between the densities of K and Sb , or AU=8'111 . The platinum weights contain about 57595 grains , the brass weights about 5760 grains each . Hence log vSp = 2-43430 , log vRS = 2*43430 , log ^K = 2-85766 , log vSb =2*845 13 , logt ; U=2*85135 . The temperature and pressure to which it will be most convenient to reduce the weighings , is the mean of the temperatures and pressures observed during the comparisons of Sp and RS with U. This , taking into account the number of observations in the two cases , is , thermometer = 65*66 Fahrenheit , barometer =29*75 English inches . When both the weights are of brass , or both of platinum , the reduction is so small as to be insensible . In the interval between 1829 and 1844 , the difference between the two platinum troy pounds Sp and RS had undergone no very sensible relative change . If , as appears highly probable , Sp and RS have undergone no sensible absolute change , Sb has gained 0*0046 grain , and K has lost 0*0061 grain . In 1844 , Sb+K=Sp+RS+0*0333 grain . Assuming Sp and RS to have experienced no change since 1829 , Sp+RS=2UO'Olll grain ; whence Sb+K=2U +0-0222 grain . The equations 11 ... 18 give 2Ex=Sb + K-(M)024=Sp + RS + < W)309 2L = Sb +K+ 0-0080=Sp + RS + ( H)413 2Ed=Sb +K+ 0-0191 = Sp + RS + 0-0525 2T > =Sb +K+ < H > 274=Sp + RS + 0-0607 The first column of the following Table exhibits the errors of Ex , L , Ed , D , as deduced from the above equations ; the second column exhibits the errors of the same weights , as determined by Captain Kater , in 1824 , by direct comparison with U ; the third shows the increase of weight of the several troy pounds in the course of twenty years . In 1844 . In 1824 . ExU= + 0-0099 Ex-U= + 0-0010 0:0089 L -U= + 0-0151 L U= +0-0005 0-0146 EdU= +0-0206 EdU=0-0015 0-0221 D U= + 0-0248 D U= + 0*0022 0-0226 In 1824 , RM=U+0'0021 grain ; in 1829 , RM=U+0'0089 ; consequently RM gained 0*0068 grain in five years . With the single exception of K , all the new brass weights have become heavier since they were first compared with U , in consequence probably of the oxidation of their surfaces , while U , which was made in 1758 , was preserved from further change by the coat of oxide already formed* One of these , Sb , appeared to have been protected by gilding , though imperfectly , as parts of its surface were slightly tarnished . Ex and L were brighter than Ed and D. K , though it had become lighter , was much tarnished , yet exhibited no traces of abrasion . The discordances presented by the different weighings of K previous to 1844 were highly perplexing , and were probably the cause of the very numerous and accurate comparisons of the various troy pounds placed at the disposal of the Committee , with the lost standard , on which alone the possibility of restoring it with sufficient accuracy depends . Professor Schumacher received K in March 1827 , accompanied by a statement that it had been found by Captain Kater to exceed the standard very little , not more than 0006 grain* . In June 1828 , Captain Kater compared a second weight Kn with each of two troy pounds in his possession , the errors of which were well determined . One of these was 0#0122 grain too heavy , the other 0*0267 grain too heavy . Let 2W denote the sum of these two troy pounds . Then W=U+0'0194 grain . By a Sp , RS , K , ETC , 773 mean of eight comparisons Kn=W0*0170 grain . In September 1828 , by a mean of twenty comparisons . Professor Schumacher found K=Kn+0*0198 grain ; whence K=U+0'0223 grain . In February and March 1829 , by a mean of twenty comparisons , Captain Kater found K=W+0*0065 ; whence K=U+0*0259 grain . This differs from the first result , 0*0199 grain ( not 0*0299 grain as it is erroneously printed ) . By ninety-two direct comparisons of K with the standard by Captain v. Nehus in June and July 1829 , K=U+0#0339 grain . In the autumn of 1829 Professor Schumacher compared K again with the sum of three brass weights of 5000 grains , 400 grains , 300 grains and 60 grains of platinum , with which it had been compared on its arrival at Altona in 1827 , and there was no sensible difference from the first comparison . By thirty comparisons in October 1829 and February 1830 , Professor Schumacher found K=Kn+0*0200 grain . This differs but 0*0002 grain from the result obtained in 1828 . In April 1844 , 2K=Sp+RS+0*0667 grain , Sp+RS=2U0*0111 grain . Therefore K=U+00278 grain , On taking K out of its case after I had received it from Professor Schumacher in March 1844 , I observed a small fragment of wood , like a grain of coarse sawdust , adhering to the under surface of the weight so firmly that I was unable to brush it off with a feather , and had some difficulty in removing it with a pointed bit of quill . The adhesion of the bit of wood to the weight is due apparently to the pressure produced by screwing down very tightly the lid of the box in which it was contained . Two or three similar grains were imbedded in the velvet lining of the case . In all probability this bit of wood had been attached to K immediately after its first comparison by Captain Kater , when it appeared to be 0006 grain too heavy , and previous to its comparison by Professor Schumacher with the brass weights of 5000 grains , 400 grains and 300 grains , and the platinum weights of 60 grains . By the observations of February and March 1829 , K=W+ 0*0065 grain , and by those of June and July 1829 , K=U+0*0339 grain ; whence W=U+0*0274 grain . But W=U+0*01 94 grain when first compared . Therefore in 1829 W had gained 0*0080 grain . At the same time RM , which has been very carefully preserved , had gained 0*0068 grain . In 1844 the well-preserved troy pounds Ex and L had gained 0*0089 grain and 0*0146 grain respectively , and Ed and D , which were in a less perfect state of preservation , had gained 0*0221 grain and 0*0226 grain respectively . The whole gain of K up to 1844 appears to be 0*0218 grain , about the same as that of Ed or D. If , as seems probable , K was compared with W about the end of 1826 or the beginning of 1827 , this error of +0*0218 must include the gain of W up to that period . The discordances in the weighings of K may be explained by supposing the gain of K , including that of W up to 1829 , to be 0*014 grain , and the gain from 1829 to 1844 to be 0*008 grain , since it maybe assumed that brass having a recently polished surface gains weight faster than when its surface is protected by a film of oxide ; also , that in the same interval , Sb , which was in some measure protected by gilding , had gained rather less than K , and that the bit of wood weighed 0*014 grain . 5i 2 Then , original error of K= +0'006 grain . Error of K in 1829=original error +0*014 grain ( wood ) +0*014 grain ( oxygen ) = +0*034 grain . Error of K in 1844 = error of K in 1829 -0*014 grain ( wood ) +0*008 grain ( oxygen ) = +0*028 grain . The comparisons of the troy pounds Ex , L , Ed , D with each other in 1814 give Ex+00102 grain =L+0'0061 grain =Ed=D . This result agrees with the conclusion already derived from the comparison of Ex , L , Ed , D with Sb and K , in showing that the differences between Ex , L , Ed , and D have very sensibly changed in the course of twenty years . The troy pound R , which is much tarnished , is about 0012 grain lighter than U , and therefore cannot be either of the weights used by Captain Kater in finding the errors of K and Kn . The discrepancies presented by the weighings of the brass troy pounds at different times , due to the effect of oxidation or other causes , are so large , that I resolved , with the consent of the Astronomer Royal , to rest for the evidence of the weight of the lost standard entirely on the comparisons of the two platinum troy pounds Sp and RS . In a note appended to Professor Schumacher 's paper in the Transactions of the Royal Society for 1836 , p. 471 , Mr. Bailey observes , that , for some unexplained reason , Mr. Cary , who was commissioned to construct the troy pound RS , used for this purpose some platinum of his own instead of that which was supplied to him by the Royal Society . The exchange , whatever may have been the cause of it , does not appear to have been detrimental , for the surface of RS , though certainly inferior to that of the newly made platinum kilogrammes and metre bars which I saw in Paris in 1844 , is superior to that of Sp , in which plugs have been inserted to fill up holes left by drilling out defective places , and is much better than that of the other pound weights made since of platinum prepared in England . If we consider the discordances presented by the weighings of the brass troy pounds simply as errors of observation , without paying any regard to their probable causes , the resulting value of U will not be very different from that given by the platinum troy pounds alone . By the observations of 1824 and 1829 , gr. weight . U= Sp +0-0081 30 U= RS + 0-0030 14 U= Sb +0-0103 6 U= K -0-0339 9 U=\#163 ; ( Ex + L+Ed + D)--0-0022 6 By the observations of 1844 , grRS =Sp +0-0057 Sb =Sp +0-0030 K =Sp +0-0363 Ex +L+ Ed + D=2(Sb + K ) + 0-0260 Whence , supposing the errors of the weighings to be insensible compared with the discordances of the brass troy pounds , gr. weight . 1 U=Sp + 0-0081 30 2 U=Sp + 0-0087 14 3 U=Sp+0-0133 64 U=Sp + 0-0024 95 U=Sp + 0-0261 6 The mean of all the equations gives U=Sp+0-0096 grain . Excluding the last , which depends upon the weighings in 1824 , U=Sp+0*0079 grain . Excluding all except the result of the comparisons of U with the two platinum troy pounds , U=Sp+0*0083 grain . Comparison of Thermometers . The thermometer K was supplied by the Committee of the Kew Observatory . It bears the inscription " No. 43 , Kew Observatory , July 1 853 . " It is graduated by lines etched upon the tube at every fifth of a centesimal degree . The distance between the freezingand boiling-points is about 18*1 inch . Mr. Welsh , under whose superintendence it was constructed , examined it by the method employed by Mr. Sheepshanks , and concluded that the graduation was correct throughout the scale to onetenth of a small division , or 0'*02 C. He obtained the following data for determining its boiling-point at the Kew Observatory , the stern being vertical : 1853 . Barom. Att. therm. Baroni , in millims. Reading of K. Temp , by Regnault 's Error . of mercury at 0 ' C. Tables . July 2730-039 65-5 760-47 99*98 100-02 -0-04 August 16 . 29*726 64-3 752-61 99*70 99*73 -0-03 August 17 . 29-640 63-2 750-51 99*58 99*65 -0-07 Mean -0-047 Hence the boiling-point with the stem vertical under the pressure of 760 millimetres of mercury at 0'C , is 99O#953 . The freezing-point , with the stem vertical , was 0o#04 , before boiling , and 0'*12 , after boiling . Assuming 100 ' C. to be the temperature of steam under Laplace 's standard atmospheric pressure , or the pressure of a column of mercury at 0 ' C , the height of which in millimetres is 760+1*946 cos 2 latitude +0*0001492 height in metres above the sea , the temperature of steam at Kew under the pressure of 760 millimetres of mercury at 0'C , will be 100'*016 . But the reading of K was 99'*953 . Hence , denoting by K the reading of No. 43 at the temperature t by a thermometer the freezingand boiling-points of which are accurately determined , when\#191 ; =0 ' , \#191 ; K= + 0'*12 , and when t= 100 ' , tK= +0'063 . In August 1853 it was heated to rather above 100 ' C. On December 15 the freezing-point had ascended to 0'*04 . The reading was 0'*00 when the thermometer was surrounded with broken ice , May 26 , 1855 , and also when immersed in pounded ice , July 10 , 1855 . The determination of the zero of a thermometer by ice is said to be less accurate than when snow is used . In the present instance it appears from the following comparisons to have been sufficiently exact . In February 1844 the freezing-point of a thermometer G , having an arbitrary scale , was 37*4 . In March 1845 it was 37*5 , the thermometer having been immersed in snow in both cases . In May 1855 , the bulbs of G and K being almost in contact with each other and surrounded with broken ice , the reading of G was 37*55 , while that of K was 0'*00 . In July 1855 , the reading of G , when immersed in pounded ice , was again found to be 37*55 . In March 1855 , by a mean of ten comparisons , the reading of G was 48*541 , when that of K was 2Of365 . By a mean of ten other comparisons , the corresponding readings of G and K were 90o#797 and 11O#432 respectively . Hence , one part of G=0o#2145 . If we suppose the zero of G unchanged since 1845 , the freezing-point of K would be 0o#004 . But if we suppose the zero of G to have been correctly determined by immersion in ice in May and July 1855 , or that the zero had ascended 0*05 part =0o#011 since 1845 , the freezing-point of K would be +0''007 . Assuming the freezing-point of K in 1855 to be 0''00 , as given by observation , the corrections of K will be , t.\#191 ; -K . t.\#191 ; -K . t. t-K . 0 ' 0-000 35 0*020 70 -0-040 5 -0-003 40 -0-023 75 -0-043 10 -0-006 45 -0-026 80 -0-046 15 -0-009 50 -0-029 85 -0-048 20 -0-011 55 -0-031 90 -0-051 25 -0-014 60 0\#187 ; 034 95 -0-054 30 -0-017 65 -0-037 100 -0-057 The thermometers B , C , D were made by the late M. Bunten of Paris . They are all divided into centesimal degrees by lines etched upon the tubes . The graduation of B extends from -23 ' up to +107 ' . It bears the inscription ' 25 My 1843 . Divise le 18 My 1844 . ' The graduation of C extends from -24 ' up to +41 ' . It is dated 1841 . The graduation of D , which is also dated 1841 , extends from -25 ' up to +53 ' . The graduation of B was examined at certain points of the scale by the method described by Professor Forbes in the Transactions of the Royal Society for 1836 , p. 578 , and the boilingand freezing-points determined , in order that the other thermometers might be referred to it as a standard . It was not , however , used as a standard , in consequence of the acquisition of the Kew thermometer , which has a scale of much larger dimensions , and is more accurately and closely divided , and also on account of the inconvenience in using it as a standard , arising from the large amount of the displacement of its zero . Immediately after boiling , February 1 , 1845 , the freezing-point of B was 0''20 ; on February 4 it was 0'*15 ; on March 3 it was 0' 'll ; in December 1846 it was 0''00 ; and in July 1855 it was +O'-ll . The depression of the zero , which in the present case amounts to 0''31 C , depends upon the composition of the glass , and perhaps also upon the manner in which it is worked by the glass-blower . Legrand observed depressions of from 0o#3 to 0'*5 in thermometers by M. Bunten * . Despretz found changes amounting to 0o#47 , 0'*45 , 0'-23 , 0'-30 , 0'-57 , 0'-61 , 0''605 0'-60 ; and that the freezing-point became stationary at the end of about four years *f ' Mr. Welsh has observed a depression in the thermometers constructed at Kew varying from 0o#09 to O0#ll . In the thermometers employed by Mr. Sheepshanks it amounts to about 0'*17 . In ten different thermometers examined by Dr. Lamont , the depressions were 0o#31 , 0o#28 , 0''45 , 0'-25 , 0'-31 , 0'-37 , 0'-62 , 0'25 , 0''31 , 0''27 respectively . He also found that it takes about five years for the zero to regain its permanent position after boiling J. The depression of the freezing-point of B below +O0#ll , from March 1845 up to January 1851 , is represented with sufficient accuracy by 0*0044 m2 , where m is the time in months up to the middle of January 1851 . The computed depressions are , 1845 . March , April 0-22 1846 . May , June 0-14 1847 . DecemberFebruary ... 0*06 May 0-21 July , August ( H3 1848 . March June 0-05 June , July 0*20 September , October ... 0-12 JulySeptember 0-04 August 0*19 November , December . 0*11 October February ... 0-03 September , October ... 0-18 1847 . JanuaryMarch ( HO 1849 . March July 0-02 November , December. . 0*17 April June 0-09 August February . 0*01 1846 . January , February 0-16 July , August 0*08 1850 . MarchDecember* ... 0*00 March , April 0*15 September November 0*07 Means of Comparisons of B and K in February and March 1855 . No. of comparisons . B. K. B K. Kt B-t . 10 4-895 4*712 0-183 0-003 0-186 10 5-344 5-177 0-167 0-003 0-170 10 6-319 6-143 0-176 0-003 0-179 10 9-219 9-016 0-203 0-006 0-209 10 10-740 10-493 0-247 0-006 0-253 10 12-893 12-652 0-241 0-008 0-249 10 14-532 14-279 0-253 0-009 0*262 10 15-336 15-095 0-241 0-009 0-250 10 16-379 16-126 0-253 0-009 0-262 10 17-581 17-329 0-252 0-010 0-262 10 18-000 17-749 0-251 0-010 0-261 10 18-000 17-750 0-250 0-010 0-260 10 18-180 17-917 0-263 0-010 0-273 10 21-382 21-116 0-266 0-011 0-277 10 23-202 22-919 0-283 0-013 0-296 10 25-331 25-045 0-286 0-014 0-300 t. B-t . t. B-t . t. B-t . t. B-t . 0 0-11 7 0-19 14 0-25 21 0-28 1 0-12 8 0-20 15 0-25 22 0-29 2 0-13 9 0-21 16 0-26 23 0-30 3 0-14 10 0-23 17 0-26 24 0-30 4 0-16 11 0-25 18 0-26 25 0-30 5 0-17 12 0-25 19 0-27 6 0-18 13 0-25 20 0-28 * Annals de Chimie , 1836 , tome lxiii . p. 368 . f Ibid. 1837 , tome lxiv . p. 312 . t Jahresbericht der Munchener Sternwarte fur 1852 , S. 64 , 93 , 101 ; and Annalen fur Meteorologie , 1842 , Heft iv . S. x. xv . Comparisons of C , B , D in July 1855 . No. of comparisons . C. B. D. 10 19-884 20-258 19-967 10 20-535 20-885 20-616 Mean of 20 comparisons ... * 20-209 20-571 20-291 Hence , at 20 ' , B-C= +0-362 , BD= +0*280 . Also , by a mean of 11 comparisons at 20 ' , KC= +0*107 , KD= +0*040 . By 30 comparisons at 18 ' , and 10 at 21 ' , B K= +0261 . Therefore B C= +0*368 , BD= +0*301 . The resulting mean value of the depression of the zero of B is 0'*12 . The value deduced from the observations of the freezing-point is 0'*13 , Comparisons of C , B , D in September 1846 . No. of comparisons . C. B. D. 10 26-551 26-884 26-750 10 25-385 25-695 25-516 10 24-401 24-670 24-531 10 23-448 23-725 23-577 10 26-634 26-949 26-796 10 23-646 23-940 23-774 Mean of 60 comparisons ... 25-011 25-311 25-157 Hence , at 25 ' , B-C=+0*30 , B-D=+0*153 . By a mean of 16 comparisons of C , B , D between 23'*9 and 26 ' % in July 1855 , their corresponding readings were c. b. d. 25-081 25-487 25-204 Hence , at 25 ' , B-C = +0*406 , B-D=+0*283 . Also , 17 comparisons of C , K , D , gave KC=+0*124 , KD=-0*007 , and 10 comparisons of B , K , gave B-K=+0*286 . Therefore B-C= +0*410 , B-D =+0*279 . The resulting mean value of the depression of the zero of B is 0'*12 , the same as its calculated value . The thermometers G , L have arbitrary scales , the divisions of which are traced on the tubes with a diamond point at every tenth of an inch . The parts of the scales of G , L , as well as those of B , C , D , K , are subdivided to hundredths of an inch by sliding scales of glass . The division of the sliding scale which is brought into apparent coincidence with the extremity of the thread of mercury , is viewed through a hole in a plate of brass attached to a very light brass frame which carries the scale , so that the direction of vision may be perpendicular to the axis of the tube . The hundredths of an inch are subdivided by estimation . Means of Comparisons of G and L with K in February 1855 . No. of comparisons . G. K. 10 48-541 2-365 10 90-797 11-432 10 111-350 15-753 10 124-050 18-389 No. of comparisons . L. K. 10 51-465 15-753 10 54-545 16-089 10 73-010 18-389 10 92*384 20-828 10 94-698 21-055 10 94-869 21-079 10 97-790 21-448 10 101-515 21-911 By a mean of 30 comparisons of G and L between 17 ' and 20 ' in July 1846 , their corresponding readings were G. L. 120-897 67-591 Means of Comparisons of G , K , L in March and May 1855 . No. of comparisons . G. K. L. 11 117-79 17-08 62-38 10 124-24 18-43 73-36 6-45 1-35 10-98 1 part of G=0'-2093 , 1 part of L=0'-12295 , 1 part of G= 1-702 parts of L. Mean of all 120-860 17*723 67-609 In July 1846 the corresponding readings of G , L were 120*897 and 67*591 . By the observations of 1855 , K= 17731 when G= 120*897 , and K= 17*721 when L=67*591 . Hence L stood 0o#01 higher , compared with G , in 1855 than it did in July 1846 . Between March 1845 and May 1855 the zero of G appears to have ascended 0'*01 . It is probable that the whole or , at any rate , the greater part of this ascent occurred before July 1846 . On this supposition , in July 1846 , the depression of the zero of G below its permanent place would be 0'*00 , and that of L would be 0'*01 . The thermometers H , P were used only in the earlier observations . The divisions of H were on the tube . The scale of P was traced on paper and enclosed between the tube of the thermometer and an exterior tube of glass joined by fusion to the thermometer tube at the lower end , and sealed at the upper end . The freezing-point of H was +0'*50 . The freezing-point of P was +0'*25 . By a mean of 13 comparisons of H , P , C , D , their corresponding readings were h. p. c. D. 3-31 h 3-13 2-93 2-99 Let 2M=C+D . Then the corresponding readings of H , P , M , t will be H. P. M. * . t-H . / -P . 3-31 3-13 2-96 2-91 -0*40 -0-22 The thermometer R was used in some of the earlier observations . It has an ivory scale the dimensions of which vary with the quantity of moisture present in the atmosphere , and consequently the error is very sensibly different at different times . By a mean of twenty comparisons of R , B in October 1846 , their corresponding readings were : R. B. B-R . 19*31 18-90 -0-41 But in October 1846 , at 19 ' , / B= 015 . Therefore tR= 0'56 . Comparison of Barometers . Up to the end of August 1844 a siphon barometer by the late Mr. Robinson was employed . It resembles Bunten 's improved Gay-Lussac 's barometer in all respects except that it is graduated in English inches , and the attached thermometer in degrees of Fahrenheit 's scale . The observations were reduced , for the mercury to 32 ' Fahr. , and for the scale to 62 ' Fahr. , by the tables in Schumacher 's Jahrbuch fur 1837 . From the beginning of September 1844 a cistern barometer by Ernst of Paris was used . It is graduated in millimetres , and the attached thermometer in centesimal degrees . In the following comparisons with the barometer of the Paris Observatory , made by one of the Assistants of the Observatory , O , T denote the readings of the Observatory barometer , and of its attached thermometer ; F , E those of Ernst , and of its attached thermometer . O. T. F. E. O-F . mm. mm. mm. 753-16 21-4 752-90 21-0 0-26 753-64 21-8 753-30 21-3 0-34 754-00 22-3 753-60 21-7 0-40 754-14 22-3 753-70 21-7 0-44 754-32 22-5 753*90 21*9 0-42 757*40 21-1 757-00 20-9 0*40 756-90 22-4 756-50 21-7 0-40 758-64 19-5 758-25 19'3 0-39 758-20 21-7 757-70 21-1 0-50 Mean 0-393 Ernst stands 0*393 millimetre lower than the Observatory barometer . The latter requires no correction . Ernst was suspended close to the Observatory barometer all night previous to the day on which the comparisons were made , their temperatures must , therefore , have been very nearly equal . Yet E is less than T , while , by a subsequent comparison with B , E was found to be 0'*45 too great . There is reason to believe that this discrepance is due to the lodgment of a small quantity of mercury in the upper end of the tube of the thermometer , which occurs sometimes after the instrument has been conveyed in a carriage over a rough pavement , as was done previous to its comparison with the Observatory barometer . In March 1845 the thermometer B was suspended so that its bulb was in contact fVeight of Air . According to Ritter* the observations of Regnault^ show that in Paris , lat. 48 ' 50 ' 14 " , 60 metres above the level of the sea , a litre of dry atmospheric air at 0'C , under the pressure of 760 millimetres of mercury , weighs 1*2932227 gramme . Assuming that atmospheric air contains on an average 00004 of its volume of carbonic acid the density of which is 1*529 of that of atmospheric air , the weight of a litre of dry atmospheric air containing its average amount of carbonic acid , under the circumstances already stated , will be 1*2934963 gramme . It appears from the discussion of pendulum experiments by Mr. Baily^ ; , that if we take G to denote the force of gravity at the mean level of the sea in lat. 45 ' , the force of gravity in lat. X , at the mean level of the sea , = G(1 -0*0025659 cos 2K ) . Poisson S has proved that the force of gravity in a given latitude at a place on the surface of the earth at the height z above the mean level of the sea = < 1 ( 2g / rx ( f'rce 'f gravity at the level of the sea in the same latitude ) , where r is the radius of the earth , g its mean density , and g1 the density of that part of the earth which is above the mean level of the sea . If , as is probable , g':g=5:ll , 21^=1*32 nearly , r=6366198 metres . Hence the weight in grammes of a litre of dry atmospheric air containing the average amount of carbonic acid , at 0 ' , and under the pressure of 760 millimetres of mercury at 0 ' , at the height z above the mean level of the sea in lat. X , is 1 2930693 ( l 1 *32 Cj ( 1 0*0025659 cos 2X ) . Regnault found the expansion of air from 0 ' to 100 ' , under constant pressure , equal 0*36706 of its volume at 0 ' ; also that , at 50 ' , the mercurial thermometer was a little in advance of the air thermometer || . The difference between the mercurial and air thermometers , at 50 ' , amounts to about 0'*2^[ . Hence , the expansion of air between 0 ' and 50'*2 is 0*18353 of its volume atO ' ; or , between 0 ' and 50 ' , the ratio of the density of air at 0 ' to its density at t ' is 1+0*003656* . The density of the vapour of water is 0*622 of that of air . Hence , if t be the temperature of the air , b the barometric pressure , v the pressure of the vapour present in the air , b and v being expressed in millimetres of mercury at 0 ' , at a place on the surface of the earth at a height z above the mean level of the sea , in lat. X , the weight in grammes of a litre of air will be\#191 ; s to..\#171 ; # < .-*\#171 ; \#187 ; \#187 ; \#171 ; .\#171 ; \#187 ; \#187 ; > . In the cellar under the Mineralogical Museum in Cambridge , where the weights were compared , in lat. 52 ' 12 ' 18 " , about 8 metres above the mean level of the sea , this becomes 1*293893\#191 ; O ; 378i > 1+0-003656* 760 Since a litre is the volume of 1000 grammes of water at its maximum density , the above expression , divided by 1000 , gives the ratio of the density of air to the maximum density of water . The logarithm of the ratio of the density of air at f , to the maximum density of water , is obtained by adding the logarithm of b0*378t > in millimetres to log At . Table I. 10+logl-293893 3 log 760 log ( 1+0-003656 0 . t. 10+ log kt . Diff. 0 4-231085 ipssp 1 4-229500 ipssp 'llS 2 4-227921 579 3 4-226347 XH4 4 4-224780 *5 ; 7 5 4-223217 5I6 4-221661 l5$o 7 4-220110 I551 8 4-218565 I545 9 4-217025 I54 ' 10 4-215490 *535 11 4-213961 J529 12 4-212437 *524 13 4-210919 l$ 14 4-209406 lSl3 15 4-207898 l$'* t. 10+ log At . Diff. 15 4-207898 16 4-206396 WH 17 4-204898 I49* 18 4-203406 I4\#163 ; 2 19 4-201919 4\#171 ; 7 20 . 4-200436 I4'3 21 4-198959 J477 22 4-197488 47J 23 4-196020 I4'\#187 ; 24 4-194558 I4'2 25 4-193101 I4*7 26 4-191648 I4*2 27 4-190201 H47 28 4-188758 I443 29 4-187320 I43\#187 ; | 30 4-185887 I433 The logarithms in the preceding Table , when diminished by 0#000028 , serve for the reduction of the weighings in Somerset House , lat. 5 Io 30 ' 40 " , 29*56 metres above the mean level of the sea ; and when diminished by 0*000132 , they may be used for the reduction of weighings in Paris . According to a document to which the names of Biot , Regnault , and Bianchi are appended* , the pressure of vapour in rooms that are not heated artificially , in Paris , is two-thirds of the maximum pressure due to the temperature . It is probable that in Cambridge the hygrometrie condition of the air is very nearly the same . The discordances which these tables exhibit are partly due to errors in the assumed expansions of brass , glass and mercury , on which , by the nature of the experiments , the value of the expansion of water is fnade to depend . Stampfer deduced the expansion of water from the apparent weight of a hollow cylinder of brass suspended in water . The coefficient of the linear expansion of the brass was found to be 0*0000192 , by experiments in which the variations of temperature amounted to from 38 ' to 62 ' ( the absolute temperatures are not given ) . At about 17 ' Mr. Sheepshanks found the coefficient of expansion of cast brass equal to 0-00001722 . This is 0*00000153 less than the mean coefficient of expansion from 0 ' to 100 ' , assuming the latter to be 0*00001875 . The error of the assumed expansion of the cylinder at ordinary atmospheric temperatures will probably be not quite so large . If taken equal to 000000133 , the correction will be 0*000004(\#191 ; 4 ) . Despretz experimented with thermometers filled with water . The expansion of the glass was inferred from the apparent expansion of mercury in the thermometer from 0 ' to 28 ' , using for the coefficient of the expansion of mercury 0*00018018 , the value obtained by Dulong and Petit . But the expansion of mercury from 0 ' to 28 ' is 0*005032 according to Regnault* . The resulting mean coefficient of expansion is 0*00017971 . Hence the expansions obtained by Despretz must be diminished by O'OOOOOO47(\#163 ; 4 ) . Pierre and Kopp , who employed the same method , deduced the expansion of the glass from the apparent expansion of the mercury from 0 ' to 100 ' , assuming its absolute expansion between those points to be 0*01 801 8 . But the absolute expansion of mercury from 0 ' to 100 ' is 0018 153 . The glass used by Pierre contained oxide of lead , and probably had very nearly the same rate of expansion at both high and low temperatures . It is not known how far the glass used by Kopp possessed this property . Hence these expansions require the addition of 0*00000135(^-4 ) . The observations of Plucker and Geissler extend only to 12 ' . They were made with a thermometric apparatus the capacity of which is compensated by mercury so as to be invariable , or very nearly so . Assuming the expansion of mercury from 0 ' to 100 ' to be 0*018018 , the cubic expansion of the glass from 0 ' to 100 ' , deduced from the apparent expansion of mercury , is 0002818 . But according to REGNAULT-fthe coefficient of the cubic expansion of a glass free from lead was 0*00002761 from 0 ' to 100 ' , and 0*00002628 from 0 ' to 10 ' . It is therefore probable that the coefficient of the cubic expansion of the glass has been taken 000000 133 too great . Also the quantity of mercury used for compensating the expansion of the glass will be too small in the ratio of 0*000179714 , the rate of expansion of mercury from 0 ' to 10 ' , to 0*00018153 , the rate of expansion of mercury from 0 ' to 100 ' . Hence , upon the whole , the expansion must be diminished by 0*0000013(i-4 ) . The ratios of the maximum density of water to its density at t ' , according to the Let t be the temperature of the air in centesimal degrees , b its pressure in millimetres of mercury at 0 ' , v the pressure of the vapour contained in it , also in millimetres of mercury , A=o0*378v , AP , AQ ratios of the densities of P and Q at 0 ' to the maximum density of water ; ePt , eQt the expansions in volume of P and Q. Then log weight in grains of the air displaced by P= log h+ logA , + log(l+eP\#163 ; )+log weight of P in grains log AP . If w be taken to denote the volume of P at 0 ' , the unit of volume being the volume of a grain of water at its maximum density , log vV= log weight of P in grains log AP . The expression for the weight of air displaced by Q differs from the above only in the substitution of Q for P. The value of A is deduced from b by means of Table IL , assuming that the amount of vapour in the air is two-thirds of the quantity in saturated air . Table I. gives the second term for the expression for the weight of the air displaced , and Tables IIL , IV . , V. give the third term according as the weight is of brass , bronze or platinum . Calculation of Densities . Let P in water at f appear to weigh as much as Q in air . Then weight of water at t ' displaced by P= weight of Pweight of Q+ weight of air displaced by Q , log vV= log weight in grains of the water displaced by P+ log W , log ( l+eP\#191 ; ) , where Wt is the ratio of the maximum density of water to its density at t ' obtained from Table VI . Log AP= log weight of P in grains 'ogvJ* . An approximate value of up having been found by assuming the weight of P equal to its apparent weight in air , this value of w may be used in reducing the weight of P , and thus a more accurate value of w obtained , by means of which a closer approximation to the values of the absolute weight of P and of AP may be found . This process is to be repeated when greater exactness is required . Densities of the Troy Pounds constructed in 1758 . Though it appears that only two of the five weights with which U was compared are in a state of unexceptionable preservation , and the number of trustworthy comparisons is reduced from 608 to 440 , these are amply sufficient for the purpose of ascertaining the apparent weight of U in air ( \#191 ; =65-66 F , e=29#75 inches ) . But , in order to find the absolute weight of U , or indeed its apparent weight in air of a density different from that which it has when\#191 ; =6566 , \#191 ; =2975 , a knowledge of the volume of the lost standard is requisite . It is not probable that U was ever weighed in water , and certainly no record of any such weighing is known to exist . There is therefore no direct method of finding its volume . An indirect way of arriving at it was suggested to Professor Schumacher by an examination of three Parliamentary Reports , the first presented May 26 , 1758 , the second April U , 1759 , and a third ordered to be printed March 2 , 1824 . It appears from the first of these Reports that Mr. Harris , then Assay-Master of the Mint , presented to the first Committee three troy pounds made under his direction , one of which was the lost Imperial Standard Troy Pound . The third Report contains the evidence of Dr. Kelly , who in reply to the query , " What was effected with regard to weights and measures by the Committee of 1758 ? " answers , " They ordered three several troy pounds to be adjusted , under the direction of Mr. Harris , the then Assay-Master of the Mint . One of these was placed in the custody of the Clerk of the House of Commons ; another was left with Mr. Harris , and is now in the possession of Mr. Bingley ; and the third was , I understand , delivered to Mr. Freeman , weight-maker to the Mint , the Exchequer and the Bank of England , who used it as his standard , and it is still so employed by his successor Mr. Vandome . " The same page contains the following note : This weight [ Mr. Bingley 's pound ] was produced to the Committee , by Mr. Bingley , who said it had formerly belonged to Mr. Harris when he held the situation of Assay-Master . There was a memorandum on the lid of the box in which it was kept , stating that Mr. Harris had made from it the pound weight which was placed in the custody of the Clerk of the House of Commons by direction of the Committee of 1758 , and which is commonly called the Parliamentary Pound . Professor Schumacher then observes that " if Dr. Kelly 's statements be exact , as there is no doubt they are , and Messrs. Bingley 's and Vandome 's pound be really the two remaining weights of the often mentioned three which Mr. Harris presented to the Committee of 1758 , we can still either determine , with the highest degree of probability , the specific gravity of the lost Imperial standard troy pound , or know with certainty that all hope to arrive at this knowledge is lost . It will be only requisite to ascertain with the greatest care the specific gravities of both pounds , the one in the possession of Mr. Bingley , the other in the possession of Mr. Vandome . If the specific gravity of both is found the same , we might from that circumstance draw the highly probable conclusion , that the three single pounds of Mr. Harris , according to my hypothesis , were really made of the same identical metal ; and the specific gravities of the two remaining pounds might with safety be considered as that of the lost standard . If , on the contrary , the two remaining pounds prove to be of different specific gravities , the hypothesis that all three were made of the same metal is evidently erroneous , and nothing can be inferred from the specific gravity of either of the two remaining . " These two weights were found to be still in existence . Mr. Vandome readily consented to allow the troy pound in his possession to be experimented upon by the Committee . In form and size this weight very closely resembles the figure of the lost standard given by Captain v. Nehus . The V. Fig. 1 . y , iKfSWjI[ 1758 upright stroke of the 5 in the type appears to have been broken off , and the defect supplied in the inscription by a cut with a chisel . The letters SF are impressed diametrically opposite to the T. This weight , as well as the others of the same date , is of one piece of metal , without any cavity for adjustment by the addition of bits of wire . Mr. Simms , to whom it was shown , pronounced it to be of soft gun-metal , as hard as cast brass , but not so hard as hammered brass , and , for such an alloy , a very bad casting . As the balance ordered of Mr. Barrow was not yet ready , Mr. Vandome 's troy pound ( V ) was weighed in water with a balance of 10^ inches beam by Robinson . The case of this was too small to admit a large cylinder of water , the use of which is considered essential to the accuracy of observations of this kind , and some unaccountable discordances in the weighings of V in air impair the probable accuracy of the result . For these reasons the result alone is given , omitting the details of the observations . By a mean of six weighings in water in July and August , 1843 , the density of Vat 0 ' C. appeared to be 8*15105 times the maximum density of water . This value , notwithstanding its uncertainty , was sufficiently exact for a preliminary comparison of the densities of the weights made in 1758 . The accurate determination of the density of V and of the other weights of the same date presents considerable difficulty ; for the pores in the metal are so deep , that the complete expulsion of the air contained in them is very questionable , even after prolonged immersion in boiling water . The following observations were made with Barrow 's balance under circumstances more favourable to accuracy . The glass jar containing the distilled water in which V was weighed , was 6*7 inches in diameter and 6*5 inches deep . V was suspended , from the pan of the balance , by a hook attached to a fine copper wire , 7*5 inches of which weighed about one grain . In order to expel the air adhering in bubbles to the weight , or contained in the cavities in the metal , it was placed , with the fine wire attached to it , in water in a bell-shaped jar of thin glass , just large enough to contain the weight . The jar was suspended over the flame of a spirit-lamp by a stout wire bent at its lower end into a ring into which the jar descended to its rim , and the water allowed to boil till it was supposed that the air was entirely expelled . The small jar containing the weight was then immersed in the water which very nearly filled the large jar , the suspending wire hooked on to the under side of the scale pan , and the small jar lowered till the weight hung clear of it , and then removed . The transfer of the weight from the small jar to the large one was thus effected without taking it out of the water . The counterpoise was placed in the left-hand pan of the balance ; V was suspended in water from the right-hand pan . Small weights were placed in the right-hand pan till equilibrium was produced , and the readings of the scale observed . V was then removed , leaving the hook suspended in water , and a volume of water equal to that of V added to the water in the jar ; the weights A , B , C , D , &c. were placed in the right-hand pan till equilibrium w^is again produced , and the gr. gr. gr. V displaces 0-8616 , and T0'310 displaces 0-3317 of air ( #==1613 , \#191 ; =761-27 ) . Hence V=T+02194 grain . gr. gr. gr. V displaces 0-8468 , and T0310 displaces 0-3261 of air ( \#191 ; =187 , 4=755-64 ) . Hence , in air ( \#191 ; =187 , \#191 ; =755-64 ) , V^T-03013 gr. But T =*U0-0074 gr. Therefore V^U0-3087 grain in air ( \#191 ; =187 , \#191 ; =755'64 ) , Mr. Bingley had in his possession two troy pounds of the same date . One of these ( O ) is said to be the original weight from which the standard was made for the House of Commons in 1758 . It is distinguished by a small dot under the T , and the imperfection in the type of the 5 is remedied by a cut with a chisel as in V. This weight has since ( in 1851 ) been purchased by the Committee . The other ( M ) , in which the 5 is left imperfect , and which has the mark\#169 ; O impressed on its under surface , has since been presented to the Mint by its former possessor . O. Fig. 2 . M. Fig. 3 . TIT I. I7SS I 1758\#161 ; Mr. Bingley was unwilling to permit either of these troy pounds to be weighed in water ; Messrs. Troughton and Simms were therefore commissioned to construct an instrument on the principle of the Stereometer invented by M. Say for the purpose of determining the specific gravity of gunpowder* , but with some improvements which I had described in the Philosophical Magazine for July to December , 1834 , vol. v. p. 203 , It consists of two glass tubes , PQ , DB ( fig. 4 ) , of equal diameter , cemented into cylindrical cavities communicating with each other at their lower ends , in an oblong piece of iron G. In the axes of the two cavities are holes concentric with the tubes . The hole under PQ is closed by a screw K , into the other is screwed an iron stopcock L. The upper end of the tube PQ is cemented into an iron cylinder N carrying a ring which surrounds the upper end of the tube DB . The inside of the cylinder is tapped to receive the screw of the stopcock , and the outside tapped so as to screw into the under end of a cup F , having its rim ground plane , and capable of being closed so as to be air-tight by a plate of glass E , smeared with lard . The tube PQ is graduated by lines traced upon the glass . The original tube , graduated in inches , having been broken , was replaced by a tube graduated in centimetres by M. Bunten . The subdivision is effected by an ivory scale S , of ten millimetres divided on the side next to the glass tube , to every fifth of a millimetre , attached to a rectangular rod of deal carrying frames on which filaments of silk TU , VW are stretched , and slips of brass having eye-holes so adjusted that the planes through the threads and the corresponding eye-holes may be perpendicular to the rod , the tubes being between the eye-holes and the Fig. 5 . threads , as shown in the section fig. 5 . A weak brass spring attached to the rod keeps it in contact with the tubes , with the silk threads and ivory scale close to that part of PQ which is graduated , so that it can be easily moved up and down , and is retained in the position in which it is left by the pressure of the spring . The support of the stereometer is adjusted by three foot screws till a thread of unspun silk by which a small weight is suspended , hangs coinciding with the axis of the tube DB . Within E is a cup in which is placed the solid the volume of which is sought . Mercury having been poured into D till its surface rises to P , the first division of the graduation , the mouth of the cup is closed so as to be air-tight by the plate of glass . The stopcock is then opened and the mercury allowed to escape till the difference of the altitude of the mercury in the two tubes is nearly equal to half the height of the mercury in the barometer at the time of the observation . Let the point M of the graduation mark the height of the mercury in PQ , and C the height of the mercury in DB . Let u be the volume of the air in the cup F before the solid was placed in it ; v the volume of the solid ; b the altitude of the mercury in the barometer reduced to the temperature of the mercury in PQ and BD . Then u-v= MC vol. PM . In order to find the capacity of the portion of the tube included between P and any point M in the graduation , the cup F is taken off , and the stopcock L screwed into the iron collar N. The screw K is taken out , and the tubes placed vertical in an inverted position . The tube PQ is then filled up to about 50 cm with mercury poured through a slender glass tube inserted into the opening at K. This precaution is necessary in order to prevent the formation of air-bubbles on the inner surface of the tube , which would interfere with the correct estimation of the capacity oi the tube . The stopcock is then opened , and the mercury contained in a Fig. 4 . known number of divisions of the tube suffered to run into a light glass jar in which it is weighed . This process is to be repeated till the upper end of the column of mercury descends to the point P. The stereometer was mounted in a room in Mr. Bingley 's house at the Mint , September 12 , 1843 , and a few comparisons made of the volumes of V , O , M. The results , however , in consequence of the unequal heating of different parts of the stereometer in putting it together , did not prove satisfactory . On the 16th , the volumes of O , M and C , a hollow cylinder of brass , were compared with better success . The unit of volume being the volume of a grain of water at its maximum density , these observations gave t ; O+5#3=2 ; M=#C0*6 . By observations made August 19 , 1843 , C^ 600*001 grains of brass +78*832 grains of platinum in air ( \#191 ; =24*23 , \#191 ; =756*78 ) . C in water ( \#191 ; =18*1)^-9*707 grains of platinum . Hence C in air ( \#191 ; =24*23 , \#191 ; =756*78 ) =g= C in water ( \#191 ; =18*1 ) +600*001 grains of brass +88*539 grains of platinum in air ( \#191 ; =24*23 , \#191 ; =756*78 ) . The weights displace 0*092 grain of air ; C displaces 0*810 grain of air . Hence C displaces 689*258 grains of water at 18*1 , and the volume of C at 0 ' is equal to the volume of 689*562 grains of water at its maximum density . Hence vO=683*66 , #M=688*96 . By weighing in air and in water it was found that vV=706*34 . The large differences between these numbers show that the volume of the lost standard cannot be inferred with any high degree of probability from a comparison of the volumes of the three remaining pounds . The only resource now remaining was indicated by Professor Schumacher 's remarks on the figure of the lost troy pound : " As soon as the Imperial standard troy pound was brought to Somerset House , Captain Nehus 's first care was to make an accurate drawing of its shape and marks , measuring all its dimensions with the greatest care . The annexed drawing represents this pound in its actual dimensions , and is now , since the original has been destroyed by the calamitous fire that consumed the two Houses of Parliament in 1834 , the only thing remaining which can preserve an idea of it . " An application was made to Professor Schumacher for the original drawing , if still in existence , or for any information that would show how far the accuracy of the wood engraving might be depended upon . In his reply , dated October 3 , 1843 , he wrote as follows : " The dimensions of the lost standard were only taken with a bow-legged compass in order to give an accurate drawing of the standard pound , and in this respect I called them in my papers accurate , but they certainly are not sufficient to give a near approximation of its volume . I find that he ( Captain v. Nehus ) has immediately transferred the taken dimensions to paper . This paper , with the original drawing , has served to give U. Fig. 6 . a-f jp -A j tfe 11 S8 the woodcut in the Philosophical Transactions , but to my best recollection Mr. Bailey has returned it , though I cannot find it amongst my papers . Even if you had Nehus 's original drawing you would not be able to find the volume , the only height he has measured being that of the whole pound . The heights of the points a , b9 c are only found by holding a scale in a vertical position near the pound . The diameters on the contrary are measured . " By a comparison of the figure of U with a profile of V traced mechanically , and with careful measurements of its axis and diameters , the axis and the extreme diameters of the knob and cylindrical portion of U appear to be a very little greater than the corresponding dimensions of V , the differences in other parts being exactly where we might expect the drawing to be inaccurate from the manner in which it was made . ( In the figures of the weights V , O , M , B , the dotted line is the profile of U. ) The diameters and axis of U being measured with a bow-legged compass , were more likely to err in excess than in defect . Making every allowance for this , it did not seem possible , on looking at the profiles of U and V , to suppose that the volume of U was less than that of V. But the volume of O , as well as that of M , being less than that of V , it appeared that of the three weights V , O , M , V approximated most nearly to U in volume . As the existing data were utterly insufficient to determine how much , if at all , U exceeded V in volume , it appeared safest to assume the volumes of U and V to have been equal . This course was recommended also by Professor Schumacher in his letter of October 3 , 1843 . Long after this resolution had been taken and acted upon , and the new standard constructed in accordance therewith , the troy pound O came by purchase into the hands of the Committee . The surface of O was studded with numerous small pores , showing it to be an extremely bad casting . It was only after repeatedly boiling the water in which it was suspended that the air-bubbles which attached themselves to the pores ceased to appear . It was weighed in water April 2 , and then left to dry till April 28 , when on being weighed in air it appeared to be about 16 grains too heavy . By heating it to above the boiling-point , the water that had been retained in the cavities was expelled , and the weight reduced to 5759*83 grains . Afterwards , by placing it in a jar containing water , under the receiver of an air-pump , and alternately exhausting the receiver and boiling the water , the cavities communicating with the surface were found capable of containing 21-37 grains of water . This explains the seeming paradox , that although the linear dimensions of O are hardly less than those of V , and sensibly greater than those of M and B , its specific gravity is considerably greater than that of V , and slightly exceeds that of either M or B. Of the weights used in the following weighings , those marked ( 100 ) , ( 200 ) , ( 400 ) ... , of nearly 100 , 200 , 400 ... grains respectively , are of bronze , for which log A=092260 . The smaller weights are of platinum . By a mean of four observations , April 30 , 1853 , O^(3200 ) + ( 1600 ) + ( 800 ) + ( 100 ) + ( 32 ) + ( 16 ) + ( 8 ) + ( 4)-0'1360 grain in air ( D=12 , C=122 , F=756-4 , E=ll-8 ) . 0^5699-9704 grains of bronze +59'8607 grains of platinum in air ( f=12-l , \#191 ; =755-4 ) . The Commissioners for the Restoration of the Standards of Weight and Measure , in their Report dated December 21 , 1841 , recommended that the avoirdupois pound of 7000 grains be adopted instead of the troy pound of 5760 grains , as the new Parliamentary Standard of weight , and that the new standard and four copies of it be constructed of platinum . In accordance with this recommendation , five platinum weights were made by Mr. Barrow , a little in excess of 7000 grains . The form of these pounds isthat of a cylinder nearly 1*35 inch in height and 1*15 inch in diameter , with a groove round it , the middle of which is about 0*34 inch below the top of the cylinder , for insertion of the prongs of a forked lifter of ivory . They are marked PS 1844 1 Ib . ; PC No. 1 1844 1 Ib . ; PC No. 2 1844 1 Ib . ; PC No. 3 1844 1 Ib . ; PC No. 4 1844 1 Ib . , respectively . The weight of 7000 grains might have been formed from one of 5760 grains , by the use of either a decimal or a binary system of weights . In either case , however , the number of the weights to be compared with one or the other or both of the weights of 7000 grains and 5760 grains would have been large , and the errors of the comparisons between themselves might by their accumulation sensibly affect the resulting weight of 7000 grains . Moreover , the repeated comparison of weights made up of the sum of several others , was a very troublesome process previous to the use of the method described in page 764 , which had not been thought of at the time the weights were ordered . These two evils were in a great measure avoided by the use of a platinum weight T of about 5760 grains , or , more correctly , very nearly equal to Sp or RS , and of the following series of auxiliary weights , also of platinum , and all constructed by Mr. Barrow : A , B , C , D each of 1240 grains ; F of 800 grains ; G of 440 grains ; H of 360 grains ; K , L , M , N each of 80 grains ; R , S each of 40 grains , nearly . The platinum of which the five lbs. , T and the auxiliary weights were made , was prepared by Messrs. Johnson and Cock . The numbers of the weights of each denomination , and their values , are given by the quotients and divisors obtained in the conversion of\#161 ; ygo in^ ' a continued fraction . The errors of these weights are found by the following comparisons : Sp and RS with T ; T with A+B+C+D+F ; each of the weights A , B , C , D with F+G ; F with G+H ; G with each of the weights H+K , H+L , H+M , H+N ; H with K+L+M+N+R and K+L+M+N+S ; each of the weights K , L , M , N with R+S . Sp and RS , instead of being true troy pounds , and consequently equal to U in a vacuum , had been adjusted so as to appear as heavy as U nearly , when weighed in air of ordinary density , and are therefore lighter than U by about 053 grain , the weight of the air contained in a space equal to the difference between the volume of U and that of Sp or RS . A space equal to the difference between the volume of 7000 grains of metal of the density of U and 7000 grains of platinum , contains about 0*645 grain of air . Calling this Q , PS may be compared with each of the weights T+A+Q , T+B+Q , T+C+Q , T+D+Q . In order to determine the error of the weight of U-645 grain with the greatest precision , ten weights Q of 0-645 grain each , so accurately adjusted that no sensible difference could be detected between them , a weight V of 6*451 grains , and a weight W of 12*901 grains , all of platinum , were obtained from Mr. Barrow . Then , Y and Z being platinum weights of 20 grains each belonging to the two Robinson 's balances , the following comparisons became possible : each of the weights R and S with Y+Z ; each of the weights Y and Z with W+V+ each of the weights Q ; W with V+ sum of ten weights Q ; V with the sum of the ten weights Q. In comparing PS with each of the weights T+A+Q , T+B-f Q , T+C+Q , T+D+Q , the weight Q was changed at the end of every four comparisons , and thus each of the ten weights Q used in turn in a series of forty comparisons . The following comparisons of the auxiliary weights with Sp and RS , and with each other , were made for the purpose of finding their errors preparatory to a more accurate adjustment , and in order to obtain a series of weights to be used in finding the densities of T and of the five platinum lbs. of 7000 grains each , from June 4 , 1844 , to the end of the year . In the comparisons of A+B+C+D+F with Sp and RS , X and Y denote the weights of the two detached pans . The counterpoise is placed in the left-hand pan . The numbers in each column are the readings of the scale in the position of equilibrium of the balance , when the weight at the head of the column is in the right-hand pan . In these , and all the other comparisons of weights in air , the results of the alternate weighings are arranged in separate columns . June 18 , 1844 . 100 parts =0*2208 grain . A+B+C+D+F+Y . Sp+X . A-fB+C+D+F+X . Sp+Y . 27-80 25-30 22*90 22-50 27-00 26-10 22-90 21*90 25-20 24-05 21*40 22*05 25-30 24-60 26*45 26-50 24-60 24-40 29*50 27*15 24-40 23-50 28-65 28-50 23-55 22-75 27*30 28-50 23-00 23-00 29*30 28*90 22*55 22*20 30-10 29*65 22*40 21*90 30*40 29*75 245*80 237*80 268*90 265*40 10(A +B+C+D+F+ Y)\#163 ; :10(Sp+X ) + 8*0 parts . 10(A +B+C+D+F+ X)=u:10(Sp + Y ) + 3*5 parts . A+B+C+D+ F:u:Sp+0*00127 grain . June 12 , 1844 . 100 parts =0*2293 grain . A+B+C+D+F+Y . RS+X . A+B+C+ D+F+ X. RS+Y . 21*20 20*70 18-60 19*60 19-00 21-10 18-10 20-20 19-30 21-60 18*70 20-00 19-50 20-80 18-50 20*00 19-40 21-30 19*10 19*35 18-70 20-80 18-00 19-85 117*10 126*30 111*00 119*00 6(A+B+C + D+F+Y)\#163 ; =6(RS + X)-9*2 parts . 6(A + B+C +D+ F+X)^6(RS4-Y)-8-0 parts . A+B+C+D+ F\#163 ; tRS-0-00329 grain . grains . A= 1239*88467 B= 1239-88651 C= 1239-88709 D= 1239-88618 F= 799-92526 G= 499-95990 H= 359-96598 K= 79-99241 L= 79-99109 M= 79-99258 N= 79-99333 R= 39*99625 S= 39-99629 In the summer of 1845 , after the adjustment and comparison of PS 200 times with T+0'645 grain together with each of the weights A , B , C , D in succession , the comparisons of the auxiliary weights with each other and with T presented some unaccountable discordances . By a most troublesome repetition of the weighings with different combinations of the weights , it became evident that A , C , F were subject to a very sensible fluctuation . This was at last found to be due to the circumstance that the platinum of which they were made had been very badly prepared , and contained cavities filled with a substance which attracted moisture from the air . In order to remove this injurious matter , they were digested in boiling water and then placed in a platinum capsule over a spirit-lamp , the heat of which caused a brown liquid to escape from the openings in their surfaces . After repeating this process several times till the coloured liquid ceased to appear , and till it was supposed that the whole of the deliquescent substance was removed , it was found that A , C and F had lost 0#04 grain , 0*031 grain , and 0*04 grain respectively . It now became obvious that all the weighings into which either A , B or F entered , must be repeated . This involved the rejection of the observations for determining the weight of PS , and the comparison of PS with the kilogramme , as well as those for comparing the auxiliary weights themselves . The weights lost by A , C , F were made up by the addition of bits of wire . In the following comparisons A denotes the weight marked A+0#04 grain , C the weight marked C+0'031 grain , F the weight marked F+0'04 grain . June 26 , 1846 . 100 parts =0-26694 grain . S=A + B+C + D+F . S+Y , T+X . T+X , S+Y . S+X , T+Y . T+Y , S+X . 19-97 19-80 18-00 18-24 20-04 19-40 17-44 . 18-30 20-57 18-66 17-60 18-54 20-41 18-89 17-95 18-61 19-75 18-65 17-90 17-96 19-96 19-55 17-82 18-60 19-99 18-80 17-27 18-16 18-92 18-52 17-17 18-41 18-41 18-59 18-27 18-14 18-94 17-22 17-60 18-29 196-96 188-08 177*02 183-25 20(T+ X)=20(S + Y ) + 8-88 parts 20(T+Y)=20(S + X)-6-23 parts . 40T=40(A +B+ C-fD + F ) + 0-00708 grain . < \#163 ; . 875 By the good offices of M. Arago , permission was obtained from the French Government to compare the pound with the standard kilogramme of platinum deposited in the Archives on the 22nd of June , 1799 , known as the ' kilogramme des Archives . ' The weights selected for comparison with the standard kilogramme , which henceforward will be designated by the letter 3 , were PC No. 1 and PC No. 2 , together with the auxiliary weight B and a platinum weight V of about 192#4 grains , making altogether about 15432*35 grains . In order to obtain a second comparison perfectly independent of the former , a kilogramme of bronze was constructed by Mr. Barrow , with which , after comparison with 8 , it was my intention to compare PS together with each of the four platinum copies of the pound in turn , and other platinum weights sufficient to make up a kilogramme . By some most unaccountable oversight I3 had never been weighed in water previous to its final adjustment . Afterwards , on account of its legal importance , it was considered hazardous to immerse it in water , especially as , from the method of preparing platinum at that time in use ( fusion with arsenious acid and subsequent ignition of the arsenide of platinum under a muffle till the arsenic was burnt away ) , there is reason to suppose that it is not entirely free from an admixture of arsenic which , on being wetted , might oxidize and then dissolve , and thus produce a very sensible alteration of weight . Its form is that of a cylinder of about 39*4 millimetres in diameter and 39*7 millimetres high , having its edges rounded by a surface 0*75 millimetre broad , and having a radius of about 3 millimetres . An approximate value of its density was obtained by Professor Schumacher and Olufsen in the following manner . In August and November 1831 , the density of a kilogramme a > in Professor Schumacher 's possession was found to be 2T212 , by weighing it in water and in air . In March 1832 , by measuring pairs of diameters at right angles to each other in planes cutting the axis in eight different points , and the distances between nine corresponding pairs of points in the ends of the cylinder , the volume of\#191 ; & at 0 ' appeared to be 471 14*4 cubic millimetres . In the autumn of 1834 , Professor Olufsen measured two diameters at right angles to each other at the middle and at each end of 3 , and the distances between eight pairs of corresponding points in the circular ends . The volume of & at 0 ' , deduced from these linear dimensions appeared to be 48615*4 cubic millimetres , and consequently its density 20-644 * . These measurements , though made with the utmost care , appeared to be too few , and confined to too small a number of points , to determine the density of 8 in this manner with sufficient accuracy . I therefore resolved to compare its volume by means of the stereometer , with that of a brass cylinder of nearly the same dimensions , the volume of which might afterwards be found by weighing in air and in water . The representations of M. Arago procured for me the privilege of forwarding the balance and stereometer unexamined from Havre to the Douane in Paris , where ! received them without being obliged to unpack the cases in which they were con* Schumacher 's Jahrbuch fur 1836 , p. 237 . tained . From M. Letronne and M.Lallemand , Officers of the Archives , to the latter of whom the custody of the standards was confided , I received every possible assistance . The balance was mounted on a strong and heavy carpenter 's bench in a room paved with brick , on the ground floor of the Archives . On unpacking the stereometer , the graduated tube was found to be broken , in consequence , as M. Bunten affirmed , of mere contact with a slender iron wire used in cleaning the tube with cotton wool , and left in it in ignorance of the peculiar action of iron wire on the interior of a glass tube , and not from any violent shock . M. Bunten replaced the broken tube , which had been divided into inches , by a tube divided into centimetres , and traced upon the slip of ivory a scale of 10 millimetres divided to every 0*2 of a millimetre . I procured one of Ernst 's cistern barometers , which , after hanging all night by the side of the standard barometer of the observatory , was compared with it on the following day by one of the Assistants . M. Gambey was commissioned to construct a brass cylinder , either solid or , if hollow , air-tight , nearly of the dimensions of 3 , a cylindrical cup to receive the kilogramme or the model , fitting into the cup of the stereometer , and a second cylinder closed at both ends , to fill up as much as possible of the space left vacant in the cup of the stereometer . While with M. Gambey , I ascertained that he had some platinum kilogrammes finished , with the exception of the final reduction . This appeared to be a favourable opportunity for commencing the formation of a collection of accurate copies of foreign standards , which had been recommended in Art . 33 of the Report of the Committee , dated December 21 , 1841 . Also the comparison of 3 with a copy having nearly the same density and expansion , and unalterable by mere exposure to the atmosphere , promised to be much more serviceable in finding the relation between the French and English standards of weight , than its comparison with a copy expanding nearly twice as much by heat , and having nearly three times its volume , and liable to become considerably heavier by oxidation in the course of a few years . I therefore applied to the Astronomer Royal for authority to purchase a platinum kilogramme for the use of the Committee . While waiting for his reply , I occupied myself with the comparison of a with PC No. 1+ PC No. 2+B+V . The platinum kilogramme being a cylinder without a knob , does not admit of being lifted with a fork , consequently , in putting it into the scale-pan or taking it out , it must be held in the hand , a glove or a piece of silk being of course interposed between the fingers and the weight . The insertion of the hand into the balance case , and the communication of its warmth to the weight itself , are so prejudicial to the accuracy of a weighing , that it became necessary to seek for some method of obviating this source of error . Such a method was found in the employment of the detached scalepans described in page 764 , and answered so well , that I afterwards continued to use it in comparing weights of the usual form . On the 16th of September , the Astronomer Royal having approved of the purchase of a platinum kilogramme for the use of the Committee , I procured one from ffi . 877 M. Gambe y. In form it resembles 8 , except that it is not quite so large , in consequence of the greater density of the metal of which it is composed . The cylindrical surface and the ends are very accurately worked . The metal of which it is made is greatly superior to that of which the standard lb. and its copies are constructed , as not the slightest indication of any defective place can be observed on its surface . This kilogramme will be designated by the letter ( ( \#163 ; . The comparisons of 8 with PC No. 1+ PC No. 2+B+V were now discontinued , being of secondary importance after the acquisition of ( 0 , and serving mainly to control the comparison of ( ss with 8 . A considerable number of observations were made with the stereometer on the 25th of September , for the purpose of finding the volume of 8 by comparing it with that of a hollow brass cylinder M of nearly the same dimensions . Towards the end of the series , M being in the cup , the mercury in the graduated tube was observed to descend perceptibly though very slowly . This was caused apparently by the passage of a small quantity of air into the upper part of the graduated tube , where the pressure was about half that of the external air . At first it was supposed that the air found an entrance either between the rim of the cup and the glass plate which closed it , or through the screw joint by which the cup was connected with the collar into which the graduated tube was cemented , or , lastly , through the cemented joint itself . The cement was then varnished with shell-lac dissolved in alcohol , and the screw and glass plate carefully smeared with lard , so as to render the passage of air through the joints all but impossible . The mercury in the graduated tube still continued to descend when M was in the cup , but not otherwise . It appeared therefore probable that the soldering of M had given way under the changes of pressure to which it had been exposed , so as to allow the air enclosed within it to escape slowly , when the pressure of the air in the cup was diminished . This conjecture was verified , on attempting to weigh M in water on the 22nd and 23rd of April , 1845 , when M was found to have increased in weight after being left all night in the water in which it had been weighed ; and on placing it in the receiver of an air-pump and partially exhausting the air , drops of water made their appearance at the junction of the plane and cylindrical surfaces at one end of the cylinder . It was evidently useless to continue the observations with M , on account of its presumed leakage ; a second series of stereometer observations was therefore made on the 5th of October , in which the volume of 8 was compared with that of ( 0 . Stereometer observations for Jinding the volume ofCl . At 16 ' the mercury contained in the graduated tube between 163*2 mm. and 108*9 mm. weighed 1812*35 grains , and the mercury contained between 108*9 mm. and 0*0 mm. weighed 361499 grains . Hence the mercury contained between 0 mm. and 136 mm. weighed 4532*87 grains , and each mm. of the tube near 136 mm. contained 33*38 grains of mercury . The volume of PM is expressed in terms of the 5 y2 Secondary Standards . The comparison of different brass weights with platinum weights , shows that , however carefully preserved , they are liable to gain from 0*01 grain to 0*02 grain or more in the course of a few years . Brass , therefore , unless very well protected by gilding , is quite unfit to be used in the construction of weights having that degree of accuracy which is required in secondary standards . Electro-gilding was tried in the first instance . It failed , however , to afford a sufficient protection to the metal underneath , and the weight of the pound when the gilding was completed , was so very uncertain as to render its adjustment an extremely troublesome process . It was afterwards discovered that these evils were due to the want of skill of the person employed as a gilder by Mr. Barrow , and not to any inherent defect in electro-gilding itself . Mr. Barrow then resorted to amalgam gilding . In order to adjust a weight , its* under surface , which was slightly concave , was more thickly coated with gold than the rest of its surface . If too heavy , a little of the gold was removed by rubbing it with charcoal ; if too light , more amalgam was added , and the mercury driven off by heat . Directions had been given that the weights should be made of the alloy used by Mr. Bailey for the standard yard bars , consisting of thirty two parts of copper , five of tin , and two of zinc . The densities , however , of the greater part of them indicate that these proportions have not been strictly observed . The lbs. numbered 31 up to 36 , protected by electro-gilding , were constructed by Messrs. Lad and Streathfield . The weighings were reduced with the expansions given in Table III . The observations for finding the densities of the secondary standards , and for comparing them with the platinum standard , were made in a room in the basement of my own house in Cambridge , the brick floor of which afforded a perfectly firm foundation for a strong table on which the balance was mounted . The weights employed in some of the weighings are of bronze , for which logA=0-92250 . Apparent weights of the secondary standards in water . Water . Platinum . Bronze . Air . No. of lb. t. gr. gr. t. b. 1 15-11 6163-2354 17'03 755-10 2 18-41 6161-5534 19*86 760-32 3 17-75 6157-7809 19*94 753-04 4 15-35 6163-6422 15-62 767-02 5 14-69 6132-0586 16-45 755-40 6 14-31 6155-7369 16-34 758-92 7 14-24 6138-4869 15-17 760-01 8 17*48 6143-1594 19-10 760-86 9 16-31 6047-7747 17'01 763-14 10 14-71 6155-3347 16-88 758-12 11 17*80 6163-6244 18-49 750-29 12 15-28 6159*0015 16-09 767-20 13 10-79 6169*9472 12-20 734-36 14 14-42 6161-9845 15-54 755*94 15 10-23 6162-9240 11-01 751-19 16 )7'43 6133-5979 17*93 754-30 17a 11-15 38-3615 6099-9740 12-42 758-02 The differences between two or more series of comparisons of the same weights , though small , are larger than the probable error of each series would lead us to expect . Of the errors which affect the results of weighing , some partake too much of the nature of constant errors to be fairly estimated by the method of least squares . Of this kind is the error due to small differences of temperature of the weights . Whenever it was practicable , the weights to be compared were left in the balancecase during the night previous to the day on which they were compared . This precaution , however , was in some measure defeated , when a single weight was compared with the sum of several others ; for the latter would be in advance of the former in following the changes of temperature during the time occupied by the comparisons . The effect of temperature on the apparent weight of any object appears to be due to currents of air ascending or descending , according as the weight is hotter or colder than the air in the balance-case . A brass kilogramme that had been left for several hours in the balance-case where the temperature was 5'*2 C , appeared to be about 5 milligrammes lighter after it had been heated up to 16O#4 C. The hygroscopic matter contained in some of the auxiliary weights , from which it was difficult to free them entirely by digestion in boiling water , may also have introduced a small error in one direction . In order to diminish , as much as possible , any inaccuracy resulting from this cause , all the more important weighings into which these weights entered , were made within the narrowest practicable limits of time . Many observations that could not be brought within such limits of time as were considered satisfactory , were rejected , the chance of a larger irregular error belonging to a small number of comparisons being considered less injurious to accuracy than the error in one direction to be apprehended in a larger number , extending over a considerable interval of time . That part of the weighing which depended upon the performance of the balances was most satisfactory . When the large balance , constructed by Mr. Barrow , was loaded with a pound in each pan , the probable error of a single comparison , by Gauss 's method , was 0*00056 grain , or less than one-1 2 millionth of the weight in either pan ; with a kilogramme in each pan , the probable error of a single comparison , by Borda 's method , was 0#00162 grain , or less than one-9 millionth part of the weight in either pan ; by Gauss 's method it was 0*00112 grain , or one14 millionth of the weight in either pan . Legalization of the new Standards . Legal authority has been given to the new Standard lb. and its four copies in platinum by an Act of Parliament , entitled " An Act for legalizing and preserving the restored Standards of Weights and Measures . " The most important of those provisions of the Act which relate exclusively to the Standards of Weight , are contained in the following extracts : " Whereas by an Act of the Fifth Year of the Reign of King George the Fourth , Chapter Seventy-four , ... it was enacted ... that from and after the First Day of May the Standard Brass Weight of One Pound Troy Weight made in the Year 1758 , then in the Custody of the Clerk of the House of Commons , should be and the same was thereby declared to be the original and genuine Standard Measure of Weight , and that such Brass Weight should be the ' Imperial Standard Troy Pound , ' and should be and the same was declared to be the Unit or only Standard Measure of Weight from which all other Weights should be derived , computed , and ascertained , and that ^ of the said Troy Pound should be an Ounce , and that -^ of such Ounce should be a Pennyweight , and that -fe of such Pennyweight should be a Grain , so that 5760 such Grains should be a Troy Pound , and that 7000 such Grains should be and they were thereby declared to be a Pound Avoirdupois : And whereas by the said Act Provision was made for restoring the said Imperial Troy Pound , in case of Loss , Destruction , Defacement , or other Injury , by Reference to the Weight of a Cubic Inch of Water : And whereas the said Standard Pound Troy ( was ) destroyed in the Fire at the Houses of Parliament : And whereas by the Researches of Scientific Men Doubts were thrown on the Accuracy of the Methods provided by the said Act for the Restoration of the said Standard : And whereas there exist Weights which had been accurately compared with the said Standard Pound Troy , which afforded sufficient Means for restoring such original Standard : And it having been deemed expedient that the Standard for Reference as a Measure of Weight should be a Pound Avoirdupois , there has been constructed a Pound Weight Avoirdupois equivalent to the Pound Avoirdupois of 7000 such Grains as are mentioned in the said recited Act , and Four accurate Copies of the said Pound Avoirdupois so constructed : And whereas the Standard Pound Avoirdupois so constructed as aforesaid , and the Copies thereof , are of Platinum , the Form being that of a Cylinder nearly 1#35 Inch in Height and ri5 Inch in Diameter , with a Groove or Channel round it whose Middle is about 0*34 Inch below the Top of the Cylinder , for insertion of the Points of the Ivory Fork by which it is to be lifted ; the Edges are carefully rounded off : And whereas the said Standard of Weight marked P.S. 1844 , 1 lb. has been deposited in the Office of the Exchequer at Westminster , and One of the said Copies of the Standard of Weight marked No. 1 . P.C. 1844 , 1 lb. has been deposited at the Royal Mint ; and One other of the said Copies of the Standard of Weight marked No. 2 . P.C. 1844 , lib. has been delivered to the Royal Society of London ; and One other of the said Copies of the Standard of Weight marked No. 3 . P.C. 1844 , 1 lb. has been deposited in the Royal Observatory of Greenwich ; and the other of the said Copies of the Standard of Weight marked No. 4 . P.C. 1844 , 1 lb. has been immured in the Cill of the Recess on the East Side of the lower Waiting Hall in the New Palace at Westminster : And whereas it is expedient to legalize the Standards so constructed and to provide for the Preservation thereof : Be it therefore enacted ... as follows : I. So much of the said Act of the Fifth Year of King George the Fourth as relates to the Restoration of the Standard Troy Pound , in case of Loss , Destruction , Defacement , or other Injury , shall be repealed . The said Weight of Platinum marked P.S. 1844 , 1 Ib . , deposited in the Office of the Exchequer as aforesaid , shall be the legal and genuine Standard Measure of Weight , and shall be and be denominated the Imperial Standard Pound Avoirdupois , and shall be deemed to be the only Standard Measure of Weight from which all other Weights and other Measures having Reference to Weight shall be derived , computed , and ascertained , and One equal Seven Thousandth Part of such Pound Avoirdupois shall be a Grain , and Five Thousand seven hundred and sixty such Grains shall be and be deemed to be a Pound Troy . VII . If at any Time hereafter the said Imperial Standard Pound Avoirdupois be lost , or in any Manner destroyed , defaced , or otherwise injured , the Commissioners of Her Majesty 's Treasury may cause the same to be restored by Reference to or Adoption of any of the Copies so deposited as aforesaid , or such of them as may remain available for that Purpose . " Densities , Errors , and Distribution of the Standards of Weight . The first column of the following Table contains the mark or designation of the weight ; the second , its density at the temperature of melting snow ( with one exception ) in terms of the maximum density of water ; the third , its error , in grains , when compared in a vacuum with PS , the new Imperial Standard lb. ; the fourth , its error , in grains , when compared with W , the Commercial Standard Ib . , in air of the temperature 65O#55 Fahr. , under the pressure of 29750 inches of mercury at the temperature mm of melting snow ( \#191 ; =18'7 C , \#191 ; =755*64 ) , in Somerset House , or in air for which log A=7#0783210 . The last column contains the name of the place of deposit , or of the country to which the weight has been sent . Designation . Density . In a vacuum . In air for which Distribution . logA=7'07832-10 . gr. gr. P.S. 21-1572 0*00000 0-63407 too heavy . Exchequer . No. 1 . P.C. 21*1671 0-00051 too heavy . 0-63477 too heavy . Royal Mint . No. 2 . P.C. 21-1640 0-00089 too light . 0-63331 too heavy . Royal Society . No. 3 . P.C. 21-1615 0-00178 too light . 0-63237 too heavy . Royal Observatory , Greenwich . No. 4 . P.C. 21-1516 0-00314 too light . 0-63090 too heavy . New Palace , Westminster . Sp.+V . 21-1321 0-00023 too light . 0-63336 too heavy . Observatory , Altona . Troy Pd . T. 21-1661 0-52934 too light . 0-00745 too light . Royal Observatory , Greenwich . Gilt lb. No. 1 . 8-36134 0-00732 too light . 0-01956 tpo heavy . India . No. 2 . 8-34161 0-03582 too light . 0-01132 too light . Russia . No. 3 . 8*30462 0-00510 too heavy . 0-02512 too heavy . Prussia . No. 4 . 8-36500 0-00425 too heavy . 0-03157 too heavy . Bavaria . No. 5 . 8-06122 0-01783 too heavy . 0-00734 too heavy . U.S.America . No. 6 . 8-28779 0-01714 too light . 0-00083 too heavy . Edinburgh . No. 7 . 8*12163 0*01933 too heavy . 0-01658 too heavy . Austria . No. 8 . 8-16317 0-01428 too heavy . 0*01679 too heavy . Dublin . No. 9 . 7-37614 0-11611 too htavy . 0-00426 too heavy . Canada . No. 10 . 8-28375 0-03910 too light . 0-02162 too light . Cape of Good Hope . No. 11 . 8-36302 0-04208 too light . 0-01499 too light . Sydney . No. 12 . ' 8*31919 0*02060 too light . 0-00118 too heavy . Portugal . No. 13 . 8-43179 0-03331 too light . 0-00195 too heavy . Spain . No. 14 . 8*34955 0*02844 too light . 0-00301 too light . Holland .