Ocalina arbuscola, N. Car.
Manicina areolata, Florida
Agaricia agaricites
SiderastrsBa radians
Madrepora oervicornis
Madrepora palmata



CABBONATB


FU08PHATB


WATSB AND OB-


OF LIICS.
OF LDOB.
OANIC MATTBRa.
. . 95.37.
. 0.84 ..
. 3.79


. . 96.54.
0.50 ..
. 2.96


. . 97.73.
0.53 ..
. 1.64


. . 97.30.
. 0.28 ..
. 2.42


. . 98.07.
. 0.32 ..
. . 1.93


. . 97.19.
. 0.78.
. . 2.81



Forchhammer found 2*1 per cent of magnesia in Coral-
lium rubrum, and 6*36 in Isis hippuris.
The sea-water, and the ordinary food of the polyps, are evi-
dently the sources from which the ingredients of coral are ob-
tained. The same powers of elaboration which exist in other
animals belong to polyps ; for this function, as has been re-
marked, is the lowest attribute of vitality. Neither is it at all
necessary to inquire whether the lime in sea-water exists as
carbonate, or sulphate or whether chloride of calcium takes the
place of these. The powers of life may make from the ele-



100 00RAL8 AND CORAL ISLANDS.
ments present whatever results the fonctions of the auimal
quire.
The proportion of lime salts which occurs in the water of
the ocean \a about s; to s of all the ingredients in solution. The
lime is mainly in the state of sulphate. Bischof states that the
proportion of salts of all kinds in sea- water averages 3*527 per
cent; and in 100 parts of this, 75 '79 are chloride of sodium,
9*16 chloride of magnesium, 3*66 chloride of potassium, 1*18
bromide of sodium, 4*62 sulphate of lime or gypsum, and 5*597
sulphate of magnesia, = 100. This corresponds to about 16^
parts of sulphate of lime to 10,000 of water.
