REDISTRIBUTION OF CALCIUM. 991 



eightfold in the limestones. It therefore appears that the very considerable 

 deficiency of calcium in the abundant shales and sandstones is to be 

 accounted for by the great concentration of calcium in the limestones. 

 On the hypothesis that the sum of the deficiencies should equal the excess 

 in the limestones, we have another case by which we may test the correctness 

 of the estimates of the relative quantities of the sediments. For if the 

 above supposition be true, the percentage of CaO in each of the kinds of 

 sediments, multiplied by the mass of the sediments, should, added together, 

 equal the percentage in the original rocks. Putting this in the form of an 

 equation we have: 



3.12X.65+3.29X. 30+41. 60X. 05=5.095. 



The sum, 5.095 per cent, is about halfway between Clarke's estimate of 

 1891 of the amount of CaO in the original rocks and his estimate of 1900, 

 being slightly less than the former and slightly greater than the latter. 

 Therefore, so far as the criterion of analyses is applicable, the deter- 

 minations of calcium seem to furnish a confirmation of the estimates of the 

 relative masses of the shales, sandstones, and limestones. 



In the above computation the amount of CaO in solution in the 

 ocean is not considered. According to Dittmar's estimates this amount is 

 553,000,000,000,000 metric tons of calcium, which would correspond to 

 774,200,000,000,000 metric tons of CaO. The total amount in the sedi- 

 ments on the basis of the above analyses and estimates of relative volumes 

 would be 34,391,250,000,000,000 metric tons. Therefore the amount in 

 the ocean is 2.25 per cent of the estimated amount in the sediments. 

 While the CaO in the ocean is to be regarded as derived from the destruc- 

 tion of the original rocks, this amount is so small as to be negligible in 

 comparing the amount of CaO in the original and the secondary rocks. 



The segTegation of the calcium, with the greater segregation of carbon, 

 in the limestones, is one of the most interesting and important results of 

 chemical, physical, and organic processes. (See pp. 964-966). It has been 

 pointed out that the process of carbonation in the zone of katarnorphism is 

 made effective by the concentration of carbon dioxide by plants in the belt 

 of weathering. The carbonates produced are largely transported to the sea. 

 In the sea the carbonates are thrown down by animals, and thus the lime- 



