354 The American Geologist, Dwnmber, isn 
past, for with a few insignificant exceptions all the carbonate of lime iu 
the geological series of rocks has been secreted from sea water, and 
owes its origin to organisms in the same way as the carbon of the car- 
boniferous formations: the extent of these deposits appears to have in- 
creased from the earliest down to the present geological period." 
In their report on deep sea deposits, collected by the Challenger ex- 
pedition. Messrs. Murray and Renard state that the chemical products 
formed in situ on the floor of the oceau nearly all originate in a sort of 
broth or oose, in which the sea water is but slowly renewed. Many of 
them appear to be formed at the surface of the deposit, at the line 
separating the ooze from the superincumbent water, where oxidation 
takes place. In the deeper layers of the deposit a reduction of the 
higher oxides frequently occurs, and at the surface of the mud or 
ooze there are many living animals as well as the dead remains of sur- 
face plants and animals.+ They also conclude that practically ah the 
carbon of marine organisms must ultimately be resolved into carbonic 
acid, the quantity of that acid produced in this way must be enormous, 
and cannot but exert a great solvent action not only on the dead cal- 
careous structure, but also on the minerals in the muds on the floor of 
the ocean.* Of the effect of this destructive action, they say: "In all 
cases, however, calcareous structures of all kinds are slowly removed 
from the bottom of the ocean on the death of the organisms, unless rap- 
idly covered up by the accumulating deposits, and in this way protected 
to a certain extent from the solvent action of the sea-water. It is evi- 
dent from the Challenger investigations that whole classes of animals 
with hard calcareous shells and skeletons, remains of which one might 
suppose would be preserved in modern deposits, are not there repre- 
sented: although they are now living in immense numbers in the sur- 
face waters or on the deposits at the bottom in some regions, yet all 
traces of them have been removed by solution. A similar removal of 
calcareous organic structures has undoubtedly taken place in the 
marine formations of past geologic ages."«j 
From the preceding statements it is evident that initially the greater 
part of the carbonate of lime is taken from the sea water by organic 
agency, but in the working over of this material in the chemical labo- 
ratory at the bottom of the sea a considerable portion is taken up by 
the sea water as amorphous carbonate of lime and thrown out in the 
crystalline form to form the matrix of the undissolved shells, etc. 
Mr. Bailey Willis has recently studied the question of the deposi- 
tion of carbonate of lime, and states that "chemists describe two con 
ditions under which bicarbonate of lime may be decoiuposed into 
neutral carbonate and carbonic acid: 1st. by diminution of the ten- 
sion of the carbonic acid in the atmosphere: 2d. by agitation of the 
solution." 
*Loc cit.. p. urn. 
^Report on the Scientific Result:- i>t the Voyage of H. M. S. challenger. Deei>-Sea 
Deposits. 1891. p. S3J. 
iLoc. cit.. p. 255. 
SLoc. cit., t>. 277. In this connection I wish to ask the student to read Messrs 
Murray and Irvine's remarks on pp. H7-H9. Proc. Royal Soc. Edinburgh, vol. 17. I - 
Rroc. Roy. Soc. Edinburgh, vol. 17. 1890, pp. v»4-V»r.. 
