228 CLARKE— SOME GEOCHEMICAL STATISTICS. [April 20. 



of view. In a former memoir^^ I have given a careful estimate of 

 the composition of river waters, and of their entire dissolved load. 

 This estimate is reproduced in the following table: Column I. gives 

 the average composition of the inorganic matter carried in solution 

 by rivers. In column II. the annual contribution of each radicle to 

 the ocean is stated in metric tons. 



I. Per Cent. II Metric Tons per Annum. 



CO3 3515 961,350,000 



SO4 12.14 332,030,000 



CI 5.68 155,350,000 



N03 90 24,614,000 



Ca 20.39 557,670,000 



Mg 341 93,264,000 



Na 6.40 175,040,000 



K 1. 51 41,299.000 



(Al, Fe).03 2.75 75,213,000 



SiO; 11.67 319,170,000 



100.00 2,735,000,000 



The figures in the second column represent the quantity of inor- 

 ganic matter annually removed from 40,000,000 square miles of the 

 earth's surface, the remaining area being, so far as additions to the 

 ocean are concerned, practically negligible. Interior deserts, closed 

 basins, and the circumpolar lands are left out of account. From 

 40,000,000 square miles of land, 2,735,000,000 tons of dissolved 

 matter are carried each year to the sea. This quantity, however,, is 

 not a true measure of chemical denudation. The NO3 is of atmos- 

 pheric origin or else derived from organic sources, and 8 per cent, 

 of the CO.., represents recent accessions from the atmosphere. Much 

 of the latter radicle is accounted for by the solution of limestones, 

 and was once, of course, atmospheric, but it is now a part of the 

 present erosion. Making the indicated deductions the total quantity 

 of matter transported in solution is reduced to 2,495,585,000 tons 

 annually; or 25 X 10^ in round numbers. This, with a probable 

 specific gravity of 2.6 has a volume of 0.96154 cubic kilometer, 

 equivalent to a layer 0.000009281 meter deep, or 0.0003655 inch 

 over the 40,000,000 square miles of land. At this rate the mean 



" A preliminary study of chemical denudation. Smithsonian Misc. Coll., 

 Vol. 56, No. 5, 1910. 



