NO. 5 STUDY OF CHEMICAL DENUDATION — CLARKE 9 



and in some European rivers, so that the final figures are not far out of 

 tlie way. Dr. Chase Palmer, working in co-operation with Dole in the 

 study of American waters, made more than one hundred careful deter- 

 minations of the ratio between sodium and potassium in over forty rivers, 

 and found it to be very nearly 4.2 to 1. This ratio is practicallji identical 

 with that given in my general mean, namely, 4.24 to 1, and the latter is, 

 therefore, satisfactory. 



In order to apply the foregoing averages to the discussion of either 

 chemical denudation or geological time, certain other data are needed. 

 Some of these are general, others are of the nature of minor corrections. 

 Professor J. Joly,' in order to determine the age of the ocean, divided its 

 total content of sodium by the amount annually carried into it by rivers, 

 and so deduced an uncorrected value of 97,600,000 years. The computa- 

 tion is simple enough, and is based upon the fact that sodium is less re- 

 moved from the waters than other substances ; if, indeed, it is appreciably 

 removed at all. Calcium and mag-nesium are precipitated as carbonates; 

 potassium is absorbed by clays, silica goes to form siliceous oozes. Sodium 

 alone, among the basic elements, tends to accumulate in the ocean with 

 little loss, and so to give some indication of its geological age. 



Joly, however, employed data of a defective character. Murray's esti- 

 mate of the sodium in rivers was taken, which, as we have seen, needs 

 serious modification. For the volume of the ocean he combined Wagner's, 

 or rather Karstens', estimate of its area with Murray's fi^gure for its aver- 

 age depth, and used Dittmar's analyses for the proportion of sodium in it. 

 The last datum is satisfactory ; the others need revision. 



The best estimate of the volume of the ocean is probably that of Kar- 

 stens,' 1,285,935,211 cubic kilometers. This, with Murray's figure for 

 the mean density, 1.026, gives the ocean a mass of 1,319,650 X 10^'- 

 metric tons. Assuming aai average salinity of 3.5 per cent., the total 

 saline matter in the ocean amounts to 46,188 x 10^^ tons; which, accord- 

 ing to Dittmar's analyses, is distributed as follows : 



Per cent. Metric tons X 10^^. 



CI 55.292 25,538. 



Br 188 86.8 



SO, 7.692 3,553. 



COa 207 95.6 



Na 30.593 14,130. 



K 1.106 510.8 



Ca 1197 552.8 



Mg 3.725 1,721. 



100.000 46,188.0 



The small traces of other substances in the ocean only represent insig- 

 nificant corrections to these figures. 



1 Trans. Roy. Soc. Dublin (2), vol. 7, p. 23, 1899. Rep. British Asso. Adv. Sci., 1900, p. 369. 

 2Eine neue Berechnung der mittleren Tiefen der Oceane. Inaug. Diss., Kiel, 1894. 



