Art. VIII.—Colonial Standard Survey.
By J. T. Thomson, F.R.G.S.
(Read before the Wellington Philosophical Society, Sept 30, 1876).
This is not intended to be a treatise on the methods employed in Standard Survey. Full information may be had on these by the study of technical works. All that can be attempted here is to indicate such professional measures as experience has shown to be the best for the particular circumstances of this colony.
Mr. J. A. Connell has ably discussed the subject of actual survey. So in this paper I shall confine myself as much as possible to matters not touched on by him.
To the Home country and other European nations we look for examples of the highest skill applied to the standard work—that is in the professional operations which govern detail measurements,—and ask ourselves, can the same processes be applied here, or do the wants of colonial settlement prevent this? This question, I hope, may be made clear before we come to the end of this paper.
The first step made in the great triangulation of Great Britain and Ireland, and which has since developed itself into a general and actual survey of territory and property, was the measurement of a base on Hounslow Heath in 1784, intended solely for the purpose of connecting by triangulation the observatories of Paris and Greenwich. Being thus instituted for a purely scientific object, it was continued so, and the next step was to measure an arc of the meridian, for the purpose of ascertaining the true form of our globe. After this a further extension of its operations was given to it by the commencement and combination of topographical and actual surveys in combination with the superior processes. But it must be here stated that these latter measures did not mark out and delineate new properties about to be taken possession of, but old properties already possessed and marked or fenced in. Thus the Home survey has not been one of settlement as ours in New Zealand is.
Another great point in British survey must here be mentioned, viz., that of India, embracing as it does over 1,300,000 square miles of territory, while the British Islands cover 122,000 square miles only. This was commenced by great trigonometrical operations over the Madras presidency in 1799, the primary object of which was, with other surveys of the same nature in different parts of the world, to ascertain the true figure of the earth, the subsidiary object being to provide geographical data for military topographical surveyors; and it is curious to remark that the initiatory support that great triangulation obtained both from the British and the Indian Governments was from the same motive—a motive apart from the purely scientific objects of the projectors, viz., that these operations would give opportunity for military reconnaissances, and so (especially in India) be useful in the time of war. *
[Footnote] * "Trans. N.Z. Inst." Vol. VIII., Appendix.
The system of great triangulation cast over India is not that of "net work" as cast over the British Islands, but what is technically termed "gridiron" or "chain series." In this respect it imitates the systems of Russia and France. Thus though all the immense extent of territory has been embraced, yet not more than one-fifth of the whole can be said to be triangulated. The Madras portion is an exception to the above rule only, which is "network." The "chain series" pursue meridians at intervals of 1 to 2 degrees of longitude, and follow parallels at intervals of 1 to 5 degrees of latitude. But there are several great areas unaffected even by these; such as the region east of Scinde, extending 420 miles east and west, and about 345 miles north and south, the region of Orissa, of equal extent—other regions in various parts uncovered being smaller than these.
In the series of the largest triangles theodolites 36 inches in diameter are used in India, each requiring 27 men for their transport.
At the commencement of Lambton's operations in India it is interesting to note that objections to great triangulation were raised by the eminent geographer Rennell, he proposing an astronomical instead of a geodetic basis; but Lambton, amongst other arguments in his reply, showed that in the breadth of the Indian Peninsula an astronomical error of 40 miles had occurred—in the position of the city of Arcot 10 miles and Hydrabad 32 miles, all in longitude; hence in those days longitude was the difficulty. Had the wonderful properties of the electric telegraph as applied to this very subject then been known, it is possible that the controversy would have ended in the support of Rennell, not in overturning great triangulation in its elucidating the problems of meridian arc survey, but in curtailing its extension beyond that process.
I have not been able to obtain any authentic return of the cost of great triangulation in Britain, and as there have been ample records of the same system in India, I refer to the following:—
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Sq. miles
Everest's great arc series 56,997 cost 87,833 1 11 7 per square mile
Bombay longitudinal 15,198 " 13,742 0 18 3 "
Budoan do 12,468 " 17,259 1 5 0 "
Rangheer do 16,087 " 11,837 0 14 9 "
Amua do 5,565 " 10,495 1 18 2 "
Karara meridional longitude 5,819 " 13,490 2 6 2 "
Guriwani do 6,298 " 5,301 0 17 0 "
Gora do 4,416 " 7,694 1 14 6 "
Chundwar do 3,565 " 6,450 1 16 6 "
Parimath north meridional longitude 4,765 " 5,287 1 2 7 "
Calcutta meridionial longitude 4,136 " 11,030 2 13 8 "
Highest £2 13s. 8d. per mile, lowest 17s. The mean cost of great or primary triangulation may thus be taken at £1 11s. 9d, per square mile.
Having the area of the country, therefore, to be submitted to this process, the total cost may be nearly calculated.
But the most important feature of this system of triangulation affecting colonial survey requirements is in its requiring to advance or spread out from one or two points only, from very accurately measured base lines. Thus in the British Islands, all parts of the country, have only been reached by a lapse, from the commencement, of 90 years, and what has been done for India has taken 75 years. There may be no inconvenience from this in these immemorially possessed countries, but where an unmarked wilderness is to be divided amongst an inflowing people the case is of an opposite nature. Here the wants of the people demand ubiquitous and immediate attention over the whole area of the country under the process of colonization. But to this subject I will afterwards refer, and next notice the degree of accuracy attained by great or primary triangulation.
All first efforts are necessarily imperfect, however great the skill and assiduity of the projectors, and in this most refined system of geodesy we find no exception. The original labours of Roy and Mudge, in England, and Lamb-ton, in India, have been revised in [ unclear: ] order to bring their work up to the perfection attained by modern instruments and inventions. Thus, in the first meridian arc triangulations, between Dunose and Misterton Carr (200 miles apart), the distance between Arbury Hill and Corly (a side of one of the "chain" of triangles near the middle of the arc), it was found that from the Dunose base the length was 117,463 feet, and from the Misterton Carr base, 117,457.1 feet, a difference of 5.9 feet, or 70 inches in somewhat more than 22 miles—i.e., 3.2 inches per mile. In recent times bases in Ireland have been measured by Colby's compensation bars, by which each 100 feet can be measured with an accuracy equal to half the breadth of a sharp steel point, on a plate of metal observed by a microscope. * In India the Dehhra Doon base, 7.42 miles in length, was measured in reverse order, with an error of only 2.396 inches, or about 3/10 of an inch per mile, and the Bider base, about 7 8/10 miles in length, compared with the Sironj base by triangulation and computation, though 400 miles apart, was found to have a difference of 4.296 inches, or about 5/10 of an inch per mile.
Steel chains had been used in the measurement of bases but to be abandoned, and on this subject Colonel Walker says that, "taking all circumstances into consideration, the conclusion is inevitable and irresistible that the chain base lines are worthless for the purpose of controlling the principal triangulation of this survey (of India), and more particularly that portion
[Footnote] * Markham, "Great Trigonometrical Survey of India," page 90. The Loch Foyle base measured, in this manner, nearly eight miles, or exactly 41,640.8873 feet, with an error of less than a quarter of an inch per mile.
of it which has been completed since the year 1834 with the best modern instruments. They have served the purpose for which they were immediately required, but they have been superseded by the base lines which were subsequently measured with the Colby apparatus of compensation bars and microscopes."
To the stock farmer or the agricultural settler the opinions of Colonel Walker will appear hypercritical; indeed, how earnest is he not—yet that very earnestness proves a state of views and interests irreconcilable. Where shall we draw the line of mutual concession, or shall the settler wait the pleasure of the great triangulator?
It is interesting here to remark how the modern invention of the electric telegraph has invaded the domain of the great triangulator, with whom, notwithstanding his subtle splitting of needle points, it is a rival in unravelling profound physical phenomena. Thus, in the measurement of longitude between Madras and Mangalore. * The distance by great triangulation is 20′ 36″.78: by telegraph, 21′ 35″.85; difference, 0″.93, or 13″.95 of arc. These figures are by Everest's "Elements of Globe Ellipticity," but by Clarke's the difference is reduced by 3″.5, or to 10″.45. The editor of the report remarks on this, that the fact is consistent with the result of Captain Basevi's pendulum operations, which show that the density of the strata of the earth's crust is greater under the depressed beds of the ocean than it is under the land elevated above the sea level. Thus the direction of the plumb line at Madras, on the east coast, is most probably deflected to the east of the normal to the mean figure, while at Mangalore the direction of the plumb line is deflected to the west of the corresponding normal. The length of the arc between the apparent zenith points is consequently diminished, and must therefore be less than the length deduced from trigonometrical observations.
And so also under the Himalayas we find the same law appertaining, viz., that the crust of the earth has greater density under the plains than under the huge excrescences of nature towering over them, and the laws which govern such physical conditions have been mathematically elucidated in the theory of terrestial gravity.†
I allude to these subjects in India, as it is the region of great contrasts, so it affords most apt illustrations. It is a region wherein we see enormous wealth in the few; most sordid poverty in the many. To a colony like this, it presents an aspect in which there is almost no analogy, and as principles permeate from centre to extremes, so we find that, as affecting the particular theme of this paper, there is no exception. The most profound and refined
[Footnote] * Report Indian Survey, 1872–3, page 15.
[Footnote] † Treatise by Archdeacon Pratt. "Phil. Trans.," London, 1871, p 338.
system of operations of survey in India go on concurrently, side by side, with the most rude and inaccurate. The former system, we need not say, is in the great triangulation; the latter, which may be known to few here, is the Khusrah survey, i.e., in the "property" or "field measurements" of the native officials. And so general is this latter system, that if considered as applied to the wants of the population of India, it is the rule, not the exception. Nor can it be avoided. So much so is this the case that in government hand-books Khusrah survey has been admitted to authoritative description, together with modes of distributing its errors for fitting into the minor circuits of village areas. The error of Khusrah survey extends from three to seven per cent. of the area measured,* and no wonder. As I observed it 30 years ago, in the territory of Malacca, the native surveyor was seen to be armed with only a twisted rattan of one-quarter orlong (60 feet) in length, which expanded in drought and contracted in wet one to four feet. He had no compass. With this he measured the length and breadth of the rice grounds, and estimated and plotted the divisions without regard to irregularities of boundary; but in orchards and fruit plantations, in which this country excells, the operation was even more inaccurate, for here the Khusrah surveyor, or penukur as he was called, simply measured round the area, calculating and plotting the contents from the periphery, whether the shape was round, square, oblong, or polygonal. Hence the fertile crops of lawsuits and internecine wars between neighbours, for by measurement under this rude process it is evident when once obliterated there could be no authoritative re-establishment of boundaries by actual survey.
And while I mention this professionally humiliating state of things, I must guard myself against any assumption that this is the fault of the responsible heads of the survey department there. In so vast a population as the empire of India contains, the influence of the Europeans on the internal economy of native habits and associations is as a drop in a bucket. The native is jealous and tenacious of his own immemorial ways, hence amelioration can only be by slow degrees; and that simple yet effective improvements have been brought about in a primitive mode of survey, handed down from ages, since I left the country, I am also aware, though to what extent I am unable to say.
This leads me to the remarks that we often hear from the lips of Europeans, viz., how fond the natives are of litigation. Indeed, they add, so fond are they of this that they fight till the last inch of land has been parted with, nay more till they have pawned their jewels, wives, and children, stripping themselves of their household gods, till little remains. Now India while it is the land of contrast of condition, so also is it the land
[Footnote] * Report on Indian Surveys, 1872–3.
of unsympathy. The European only scans the surface, and he little knows the forces that act underneath. That there is powerful action though unseen has been often and too conspicuously proved. But were we to place Europeans under the same circumstances in relation to that we most prize, viz., our heritable lands, how would it be with us, with the rivers spreading over our fertile fields, the exuberant vegetation obscuring our pastures and hill plantations, so that the marks are obliterated, and with no mode of practical and legal settlement, would not litigation be rife, and bloody feuds also? Then may not our unfavourable estimate of the Hindoo be harsh?
But this paper is not intended as a discussion of social or political theories, so we must confine it to the narrow professional limits, and return to its subject. Here then in India we have a proof of (as it would be esteemed in New Zealand) an utterly worthless actual section survey authoritatively in operation alongside of geodetic operations of the highest class and refinement. And when we say so we may be asked how it affects the point under consideration? The answer is in this wise, that it brings us to a conclusion contrary to popular notions, viz., that great triangulation does not guarantee correct actual survey, and it will be shown hereafter that it may even deteriorate it.
So much by way of preface. The rest of this paper will be devoted to an exposition of our views in relation to what should be the professional nature of standard colonial survey, in which the settlement of the people is the paramount object.*
At the outset of a Colonial survey it is of importance that the principles of the standard branch, should be at once determined on, and in this determination it must be considered how far professional bias must give way to the immediate wants of the settlers. If a mode of operations can be devised that administers to these wants without involving actual—i.e., recognisable practical error, it is my opinion that it would be well to accept this.
The basis of all trustworthy settlement or section survey is triangulation, of which there are three distinct systems, namely—primary, secondary, and tertiary. When I first took service in New Zealand I had the honour to advise the Government of Otago on this point, and I then suggested that primary triangulation, were it commenced in the Colony, must be executed by the General Government. † But I indicated no time when this should commence, my responsibilities being limited at that time to the Southern Province.
[Footnote] * See my letter dated June 9th, 1856, to the Superintendent of Otago.
[Footnote] † Where contrary to the state of India above depicted our position is one of close sympathy with the people, who come here to seek new homes and settle themselves.
Since then another officer has suggested primary triangulation.* There can be no question of its high value when properly executed, as by it alone geodetic or globe-form problems can be independently solved; but this value must be taken in a purely scientific sense. And the two inferior systems, though not claiming to do work in this category, may yet be of value otherwise not to be exceeded, being trustworthy within the requirements of Colonial survey operations.
The cost of primary triangulation is £1 11s. 9d. per square mile, † that of secondary, £1 7s. 9d.‡ Now, as the area of New Zealand is 102,000 square miles, the cost of each for the whole Colony respectively will be £161,925 and £141,525, or complete, as designed, £303,450. I mention the two together, because if primary triangulation be decided on, secondary is also absolutely necessary. Taking the experience of the British Islands, the time required to complete the same would be 75 years. § Thus, were the cost alone not sufficient to deter their introduction as a standard, their tardiness would. Settlers and land purchasers with their families could not wait four or five, not to mention 37 ½, years till placed in possession of their homes and title deeds.
It has certainly been suggested that actual section survey might go on in advance of triangulation by setting out the work in "approximate meridians," and substituting "rough diagrams" for properly finished plans before standard observations are made and reduced. ∥ But as the time suggested by the proposer of eight or ten years, under which the observations of the primary, secondary, and tertiary triangulations might be reduced, appears to me to be much under estimated, I turn to the highest authority on these subjects, and under whose charge are the largest trigonometrical operations of modern times. Colonel Walker, Superintendent of the Great Trigonometrical Survey of India, under date 1st December, 1870, remarks as follows¶:— "It is obvious that every operation of a survey must necessarily be fallible, and therefore that all newly obtained facts of observation that are susceptible of being combined with those that have been previously acquired are liable to disturb the results which were previously arrived at. Every additional base line, and every new chain of triangles, must necessarily exercise some influence on operations generally, and more particularly
[Footnote] * Palmer.—N.Z. Parl. papers, 1875, H.I. p. 22.
[Footnote] † Average of eleven districts in British India. Markham, I. c. page 292.
[Footnote] ‡Major Triangulation of Otago Block, 1857.
[Footnote] § Triangulation of British Islands commenced in 1784, and finished in 1874; area 122,000 square miles.
[Footnote] ∥ Palmer.—1. c. page 25.
[Footnote] ¶ "Great Trigonometrical Survey of India," Vol. I., Preface.
on those in their immediate neighbourhood. Thus, therefore, before triangulation could be finally reduced, and all its parts harmonised, it is necessary either that the whole of the angular and of the linear measurements shall be completed, or that they shall have so nearly approached completion, that what remains to be done may hereafter be fitted with what has already been done without any serious violation of principle. It is only of late years that the operations of the survey have been sufficiently advanced towards completion to justify the commencement of the final reductions. These reductions, however, are now being proceeded with, and the time has arrived when publication may be commenced."
I may add that when the above remarks were made, the primary and secondary triangulations of India had not been eight or ten years in operation, but 71 *; and lately, during many years, employing 80 officers, with their staffs, at an annual cost of £70,000. † To those having local experience it will be evident that till these reductions have been made no titles or Crown grants, based on "rough diagrams" and "approximate meridians," could safely issue. This delay, we know, would not be borne by the people and their representatives for one year, much less eight, ten, or 71 years. But to the local surveyor it will also be apparent that such an accumulation of "rough diagrams" and "approximate" bearings in the records of so large an establishment as the General Survey Department of New Zealand would amount to a vast perpetuation of the evils which it is now the object of the Government to prevent.
It is necessary here to remark that primary triangulation as applied to colonial settlement survey can scarcely be considered even as an experiment. It was attempted in Australia, but had to be discontinued, owing to its cost and tardiness. ‡ In no other part of the British dominions, nor in the United States of America, has it been applied as a concurrent and ruling process with or over settlement survey, and in regard to actual survey all that can be said of it is this, that in old, long-settled and wealthy countries, by "breaking down" the triangles it has been available in controlling the chain measurements of properties and estates, whose boundaries having been long built or fenced needed no haste for their delineation. Here the contrary is the case, for no sooner does an immigrant settler pay for his land than he expects possession and titles.
The only question of importance then that remains is this—do primary and secondary triangulation secure superior correctness in section survey? This question must be answered in the negative, as we know from actual
[Footnote] * Markham, 1. c. page 292.
[Footnote] † Report on Indian Surveys, 1871–2.
[Footnote] ‡ Report General Survey of Victoria, 1859–60.
experience. Thus the section survey in the southèrn portion of this colony has been proved by mathematical reduction to a general accuracy of within two to three links per mile, * while the average error of the surveys of British India, where ruled by primary triangulation, is twelve links per mile, † and the information that I have obtained directly from officers connected with the Ordnance Survey of England shows the error there to vary from three to fourteen links per mile. Nor is the cause of this far to seek. It lies in the fact that inordinate care and estimation of the refinements of observation re-act disadvantageously in the practical work. It reduces the status and respectability of the section surveyor, whose office, however despised and unimportant in England or India, is all important here. Hence the higher accuracy of our actual survey is due to the better class of officers employed.
But while I say so much at present, it is not to be understood that I oppose primary triangulation for all time to come; as the wealth of the colony increases, as learned classes arise, as knowledge becomes a pursuit for its own sake, as learning advances in our universities, and as our scientific societies grow in strength, the subtle and profound problems that primary triangulation elucidates will then be usefully and intelligently studied. Further, in support of this the legislature may be fairly asked to vote the cost of a staff of specially trained officers and assistants. ‡
To make myself fully understood on this subject, I may state that the main object of the promoters of primary triangulation in Europe and elsewhere is to ascertain the figure, dimensions, and specific gravity of the earth, as stated before. With these investigations, in course of time other physical problems and modes of observation have become associated, so that in these modern days the system would be held to be incomplete were they omitted. Thus originally, with the primary triangulation on a meridian, the zenith sector almost alone was had recourse to for astronomical comparison of differences of latitude. Now the electric telegraph is had recourse to for comparisons in differences in longitude. By this means abnormal conditions of the density of the earth, as indicated by pendulum operations, have been explained, and certain curious anomalies of the constitution of the solid crust of the earth have been submitted to mathematical
[Footnote] * Exposition of Otago Surveys, p. 16. J. T. Thomson, C.E., F.R.G.S., Dunedin, 1875.
[Footnote] † Report on Surveys of British India, 1871–72, p. 35.
[Footnote] ‡ The State of Massachusetts, the best settled in the United States, having been occupied since the year 1620, now moves for a primary triangulation, but only on purely scientific grounds. This is due to the influence of the wealth and intellectual preeminence of society in that state. See "North American Review," July, 1875. The Federal Government of the United States has allowed a coast primary triangulation to drag its slow course for 25 years under great difficulties.—J. T. T.
test in the theory of terrestial gravity.* Abnormal states of surface curvature have also been detected, and a consequent aberration from the true zenith. With these investigations extremely delicate levelling operations are carriėd on by which minute rise and falls in the elevation of land are made apparent—the laws of delta depositions, are also effectively elucidated. Again, tidal observations have careful and continuous attention, whereby not only the general laws that govern these undulations on the surface of the ocean are explained but all local phenomena that are connected therewith. Then also magnetic declination shares a large degree of attention in its hourly, diurnal, and annual motions. With declination is also observed the dip of the needle and magnetic intensity in different localities and latitudes. Meteorological observations are made at different elevations, etc. These minute subtle analyses of physical questions (of which the above is the merest abstract) are modern adjuncts to pure geodetic or globeform surveys, of which the basis is primary triangulation.
To propose to undertake the above system of survey, with its great prolongation of time, in this distant part of the world as a basis of settlement operations, no doubt carries a certain degree of éclât, but when practical considerations are fairly stated as I have endeavored to do, unsurmountable difficulties will be seen to stand in the way. I take it for granted then that it will be admitted that such slow and elaborate operations had better be deferred till society has grown apace, when great or primary triangulation may be undertaken, not in a perfunctory manner, which would be its necessary character at this present time, but completely and with credit to the promoters.
Hence I would advise that in the New Zealand General Survey staff only two or three officers devote themselves to purely scientific observations, such as are absolutely necessary for ruling that standard work which connects the actual with the geographical. Thus the whole force of the department, with the above exception, can be given to the immediate settlement of the inflowing people, securing, by the practical system we adopt, their boundaries and titles.
For the above reasons, and at this present period, I do not recommend the commencement of primary or great triangulation. What, then, is to be done? I reiterate that triangulation is necessary for checking section or settlement survey. For this purpose minor or tertiary triangulation cannot be dispensed with, as it alone affords points at sufficiently close distances. Hence the next question arises: Does it suffice of itself as a connecting link between the geographical and actual operations? The answer is, No.
[Footnote] * "Philosophical Transactions," London, 1871, and Report Indian Surveys, 1871–72, p. 20.
What, then, is to rule it? There are two systems which may effect this purpose, viz.—major triangulation or meridional circuit survey; and here again comes a stage of operations in which judgment must be exercised. It is a stage in which many circumstances must be considered, but the principal consist—1st, in the natural and very proper professional bias of the surveyor to aim at the refinements of observation;—this involves time and cost; and, 2nd, in the necessities of the settler to get possession of his land purchase, so that he may quickly build a house for his family. These two tendencies are evidently not in harmony, but quite the contrary; so, to meet the wants of the settler a line of concession must here again be devised by the surveyor which does not involve practical error.
As there can be no question as to the necessity of placing the immigrant in his home as quickly as possible, the only considerations, then, that we may here discuss are the relative accuracy, cost, and despatch of the two systems of standard surveys above named. On the subject of accuracy there is considerable room for differences of opinion, which I will notice as shortly as possible. Instances of the error attached to major triangulation, executed with 8 and 10-inch theodolites in New Zealand, are given at 12 inches, * 6 ½ to 14 ½ inches, * while errors attached to minor triangulation, executed with 5-inch theodolites, have been found to vary from half a link to six links per mile; but the average error, by crucial test, has been proved to be not exceeding two links per mile. † Again we have a notable example in Mr. Connell's minor triangulation of the Lake District, in Middle Island, carried over a large expanse of mountainous country, of work closing within an error of 4 ⅕ inches per mile. ‡ Thus, under somewhat incongruous testimony, we may fairly conclude that major triangulation may be admitted to have an error of one link to the mile attached to it, while minor triangulation has two links. Now, the object of stating this opinion is to enable us to compare the relative accuracy of major triangulation and meridional circuit, as the latter for its distances is dependent on minor triangulation, though its bearings are taken by the 8 and 10-inch theodolites used in major triangulation. Thus the comparison brings out this main fact, that, in bearings, the accuracy of the two systems is equal; but, in distances, one has the advantage in accuracy of less than one link per mile. Does this invalidate the meridional circuit system in the purposes of Colonial survey. I say, No. It is amply accurate for checking actual or section survey; so where the interest and comfort of the immigrant settlers require despatch it may be freely had recourse to by the surveyor in perfect confidence that it
[Footnote] * Palmer—1. c. p. 5 and 9.
[Footnote] † Thomson.—1. c. p. 15.
[Footnote] ‡ "Trans, N.Z. Inst.," Vol. VIII,—Appendix, p. 31.
will work out the problem of settlement survey correctly to the end. Thus a surveyor may professionally concede to the wants of the settler so far. I may also here, in addition, state this circumstance: that in standard survey true bearing is of more importance than distance, errors in the former not being eliminated till the boundaries of circuits are reached, while errors in distance are eliminated at boundaries of survey districts, which are limited to twelve miles square.
We next come to the relative cost. That of major triangulation, being affected by the nature of the country, has been variously stated, but we quote the following;—In Otago, 540 square miles cost £759, or £1 7s. 9d. per square mile, or about ½d. per acre. * In Auckland and Wellington, 1,019,600 acres cost £2,400, or 56/100 of a penny per acre. † Other work of a similar nature has been estimated at a rate more or less, but we may accept these as the average in accessible country.
The cost of meridional circuit survey is obtained from the operations executed by Mr. McKerrow, now chief surveyor of Otago, which covered 12,000,000 acres of territory, at a cost of £3,500; that is 3s. 6 ½d. per square mile, or 1/15 of a penny per acre. Thus the relative cost of major triangulation and meridional circuit is *53d. to *066d. or as 8 to 1 nearly. ‡ Now as cost means money and money means time, it is evident that the despatch or rapidity of meridional circuit standard survey is eight times greater than those of major triangulation. Hence its advantage in meeting the responsibilities of Government in their relations to the wants of outlying and dispersed settlers, now spreading themselves over all parts of the colony. With the immense amount of onus now on the Government to have recourse to it is not a political only but an absolute necessity. §
With these facts before us, then, we arrive at this opinion, that having abandoned primary triangulation, and secondary or major triangulation having a slight advantage (but in a professional point of view only) over meridional circuit, it should be had recourse to in carrying out the standard survey when circumstances will permit this. Hence in the revisal of all untrustworthy sectional*work, of which there are 11,095,287 acres in the colony,∥ major triangulation on carefully measured bases should be had recourse to,
[Footnote] * Major Triangulation, Otago Block, 1857.
[Footnote] † Report of Inspector of Surveys, 28th May, 1875.
[Footnote] ‡ The cost for the whole colony will be as £141,525 to £18,062 also respectively.
[Footnote] § This is the practical question in all parts of the colony. Can an immigrant settler wait eight years to get possession when he can be placed in one year by the Otago standard system of survey?
[Footnote] ∥ Palmer.—1. c. p. 28. Section surveys, 6,405,500; Native do, 4,689,787. Total, 11,095,287.
for here the areas being for the most part already settled and divided by fences, little inconvenience owing to delay can be felt by the population. Otherwise also where haste is not imperative the same system should be adopted.
It now remains for me to briefly express my views in relation to the process that may take the place of primary triangulation. These are in no way altered since I stated them fifteen years ago.* In the geographical branch the only vital argument in favour of primary triangulation was the difficulty of obtaining differences of longitude. With the introduction of the electric telegraph into the colony this has entirely disappeared. So completely is this the case that excepting for close distances the latter has an immense superiority in accuracy. Thus in the Trans-Atlantic longitude determined by the United States Coast Survey the longitude of Harvard Observatory (America) from Greenwich Observatory was found by three separate routes and sub-marine cables to this degree of exactness—
1867 4 43 31.00
Greatest error 0″.06, or 0″.9 of arc equal to 64.8 feet
† Mean 4 44 30.01
As the colony through the extension of the electric telegraph is now in a position to ascertain differences of longitude, in the same manner and with exactness relative to the size of instruments within our reach, and we may rely with perfect confidence on this system for establishing what has hitherto been the most difficult problem of geography. Hence the transit instrument and telegraph will establish our longitudes; the zenith sector our latitudes, on which at certain points the standard survey will close. This geographically binds all the processes together and completes the system.
[Footnote] * Outline of Colonial Survey, 1861. p. 5.
[Footnote] † "Electric Telegraph Journal," London, Oct. 15, 1873.