THE MINERAL MATTER OF THE SEA 479 



may be estimated. The precise changes which such rock under- 

 goes doubtless vary from point to point, and the degree of change 

 before removal by erosion must also vary. It is probably safe to 

 say that if the decomposition is measurably complete, the expansion 

 in volume would be not less than an eighth, and it might be as much 

 as a third. Let it be assumed to be one-fifth. The 55,000,000 

 cubic miles, the decomposition of which is called for to furnish the 

 sodium necessary for the salt of the sea, would then become 66,000,000 

 cubic miles, and the 145,000,000 and the 290,000,000 cubic miles, 

 the decomposition of which is called for to furnish the calculated 

 amount of calcium carbonate, would become, respectively, about 

 174,000,000 and 348,000,000 cubic miles; while the 388,500,000 and 

 418,500,000 cubic miles (p. 479), increased by one-fifth, become 

 about 466,000,000 and 502,000,000 cubic miles, respectively. These 

 figures represent, respectively, about 3, 7, 14, 20, and 21 times the 

 amount of material now above sea-level. 



Since most of the decomposed rock is believed to have been in 

 the land, and since but about 23,500,000 cubic miles now remain 

 above sea-level, and this largely undecomposed, so far as it is non- 

 sedimentary, it follows that an enormous body of rock material must 

 have been removed from the land to the sea. If the rock so removed 

 was not so completely decomposed as to yield up all its sodium and 

 calcium, the total amount would have been greater than if decom- 

 position were complete. When due allowance is made for the uncer- 

 tainties of these figures, they are still so large as to give a magnified 

 conception of the work which land waters may have done in the 

 later stages of the earth's history. The transfer from land to sea of 

 an amount of material equal to even 3 times all that that is now 

 above the sea is most impressive. The transfer of an amount 21 

 times as great as that now above the sea, is still more stupendous. 



3. The same general results may be approached in another way, 

 though the calculation is based on somewhat speculative data. It has 

 been estimated that the carbonic acid gas of the atmosphere is being 

 consumed, in the original carbonation of rocks, at the rate of 270,- 

 000,000 tons per year. 1 On the assumption that four- fifths of this 

 amount of carbonic acid gas goes to the carbonation of calcium 



1 Reade, cited by Chamberlin, Journal of Geology, Vol. VII, p. 682. 



