510 THE JOURNAL OF GEOLOGY. 



cording to Dittmar, 1 the greater part of the lime in ocean water 

 is there combined as sulphate, which in contact with organic mat- 

 ter would be reduced to sulphide with evolution of carbonic acid; 

 the latter would attack the sulphide with formation of carbonate 

 of lime and sulphide of hydrogen. Thus organic matter in river 

 waters tends to increase the proportion of carbonate of lime in 

 the zone of brackish water. The carbonate thus formed is added 

 to that already existing in the river water. 



The solubility of carbonate of lime in fresh water and in 

 salt has been an object of consideration by several experiment- 

 ers. Sterry Hunt testing artificial solutions found that I litre of 

 water which contained 3 to 4 grams of sulphate of magnesia 

 could dissolve 1.2 grams of carbonate of lime and 1 gram of 

 carbonate of magnesia ; but after standing a long time all the 

 lime was deposited as hydrated carbonate. 2 Thus it would 

 appear that the presence of the sulphate assisted the solution of 

 the carbonates. 



Experiments made by Daubree, which contradict Hunt's re- 

 sults, led Thoulet to conduct a series to determine the question. 3 

 He took several minerals, marble, shells, coral and globigerina 

 ooze, and subjected the comminuted samples of each separately 

 to the action of filtered ocean water and distilled water during 

 five weeks in each case. The solutions were shaken several 

 times each day and the water was changed from time to time. 

 At the close of the experiments the samples had lost in weight 

 and the amount taken into solution, reduced to that dissolved 

 per cubic decimeter per day, was found to be, in grammes 



Shells, ----- 



Coral, _-__- 



Globigerina, - 



'Op. cit . , p. 204. 

 2 Dittmar, op. cit., p. 209. 



3 Oceanographie (Statique) par M.J. Thoulet, 1890, p. 263, and Comptes Rendus, 

 t. CVIII, April, 1889, p. 753. 



