Page:The Journal of geology (IA journalofgeology11893univers).pdf/84

cording to Dittmar,^[1] the greater part of the lime in ocean water is there combined as sulphate, which in contact with organic matter 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 experimenters. Sterry Hunt testing artificial solutions found that 1 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 Daubrèe, which contradict Hunt's results, 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 list in weight and the amount taken into solution, reduced to that dissolved per cubic decimeter per day, was found to be, in grammes