230 CLARKE— SOME GEOCHEMICAL STATISTICS. [April 20, 



annual increment can be approximately determined. If, from the 

 yearly contributions of rivers the amount of each radicle remaining 

 in solution is subtracted, the rate of chemical sedimentation becomes 

 known. In order to make this calculation, the age of the ocean must 

 be assumed ; but variations in the latter estimate affect the results 

 but little. For example, the ocean contains 571.7 X 10^- tons of 

 dissolved calcium, which, divided by the age, gives the annual addi- 

 tion. If the age of the ocean is 100,000,000 years the annual incre- 

 ment of calcium in solution is 5,717,000 tons; if only 50,000,000 

 years it is 11,434,000 tons. Subtracting these quantities from the 

 total calcium of the river waters the remainders become 551,953,000 

 and 546,236,000 tons respectively, the difference being much less 

 than the uncertainties in the data employed. If, for the sake of 

 uniformity, we take the uncorrected age of the ocean, 83,472,000 

 years, the chemical or biotic sediments are represented by the fol- 

 lowing annual quantities. 



SO4 288.021,000 metric tons. 



Ca 550,821,000 metric tons. 



Mg 71,951,000 metric tons. 



K 34,971,000 metric tons. 



(AI, Fe)203 75,213,000 metric tons. 



SiOa 319,170,000 metric tons. 



These are the quantities of the several substances annually removed 

 from solution in the ocean, which, in combination assume the fol- 

 lowing form. 



CaCOs 1,347,440,000 metric tons. 



CaS04.2H20 50,936,000 metric tons. 



MgCOa 251,830,000 metric tons. 



K2Si03 69,045,000 metric tons. 



Limonite 87,905,000 metric tons. 



Silica 295,096,000 metric tons. 



Total 2,104,252,000 metric tons. 



The last group of figures needs some explanation. From the anal- 

 yses of oceanic sediments published in the reports of the Challenger 

 Expedition I find that the ratio between sulphate calcium and car- 

 bonate calcium is 1:45.5. Calcium, therefore, is apportioned be- 

 tween the two salts in that ratio, but much of the SO^ radicle is left 



