654 THE JOURNAL OF GEOLOGY. 



ate of lime and throwing it out in the crystalline form, accounts 

 for the filling up of the interstices of massive coral with crystal- 

 line carbonate in coral islands and other calcareous formations, 

 so that all traces may ultimately be lost of the original organic 

 structure." 1 



The authors explain the disappearance of shells and lime 

 deposits in the greater depths of the ocean by their being dis- 

 solved by the carbonic acid in the water, which is present in larger 

 quantity at great depths and also is produced by the decompo- 

 sition of the animal matter of the shell and of the various organ- 

 isms living in the water and on the bottom. They conclude that : 



On the whole, however, the quantity of carbonate of lime 

 that is secreted by animals must exceed what is re-dissolved by 

 the action of sea water, and at the present time there is a vast 

 accumulation of the carbonate of lime going on in the ocean. It 

 has been the same in the past, for with a few insignificant excep- 

 tions all the carbonate of lime in the geological series of rocks 

 has been secreted from sea water, and owes its origin to organ- 

 isms in the same way as the carbon of the carboniferous forma- 

 tions ; the extent of these deposits appears to have increased 

 from the earliest down to the present geological period. 2 



In their report on deep sea deposits, collected by the Chal- 

 lenger Expedition, Messrs. Murray and Renard state that the 

 chemical products formed in situ on the floor of the ocean nearly 

 all originate in a sort of broth or ooze, 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 fre-. 

 quently occurs, and at the surface of the mud or ooze there are 

 many living animals, as well as the dead remains of surface 

 plants and animals. 3 



^oc. cit., pp. 94-95. 



2 Loc. cit., p. 100. 



3 Report on the Scientific Results of the Voyage of M. M. S. Challenger. Deep- 

 Sea Deposits, 189 1, p. 337. 



