Professor J. Johj — Salt and Geological Time. 349 



this was of marine origin and brought with it its full equivalent of 

 sodium. We thus assume that one-third of the chlorine in rivers is 

 derived from the ocean. We will now calculate what correction on 

 the 96 millions of years this allowance will involve. 



The total chlorine discharged by rivers annually into the ocean is 

 84 X 10® tons, and 33 per cent, of this is 28 x 10'' tons ; this is, 

 we assume, derived from the ocean. Of the total CI discharged by 

 rivers we see that 56 X lO** tons (the part derived from the rocks) 

 are not cyclical. 



The 33 per cent, of chlorine which is wind-carried, as we assume, 

 has a sodium equivalent of 18-4 X 10° tons. Deducting this from 

 the total annual river supply of sodium, i.e. from 157-3 x 10" tons, 

 we have 138-9 X 10° tons derived from the rocks. 



Let now N = the sodium now in the ocean = 15,627 x 10'-. 



11 = the quantity of sodium derived from solvent 

 denudation and discharged annually by rivers 

 = 138-9 X 10°. 

 C = quantity of chlorine now in the ocean 



= 28,316 X lO'l 



c = quantity of chlorine derived by solvent denudation 



and annually discharged by rivers = 56 x 10°. 



(All in tons.) 



If now X = Geological Time, we see first that the quantity of 



chlorine cX was derived from the rocks during the time X, and 



therefore the amount C — cX must have originally been free in the 



primeval atmosphere. I have shown in my paper on the Age of the 



Earth that there is reason to believe that 6-7 per cent, by weight of 



such free chlorine would take up sodium from the earth-crust. 



Consequentl}', the weight of sodium brought in, expressed as 



a fraction of the free chlorine, is -iTro- X ff , the last fraction being 



the ratio of the combining weights. This factor becomes 0-044 



when reduced. In other words, the mass of sodium brought into th& 



primeval ocean was 0-044 (G — cX). 



Hence the equation for Geological Time will be — 



JV-0044 (C-cX) 

 X = 



n 



and from this we have — 



N- -044 C 

 ~ n - 0-044 c 



Inserting the numbers given above, we get X = 105 X 10°. 



Allowing, as I have done in my first paper, a deductive correction 

 for direct coastal denudation, wo may state our final result as just 

 about one hundred millions of years. We are not justified in stating 

 our result more definitely. We keep in mind that our knowledge of 

 river analysis and of ocean mass are certainly not final. 



So far, then, as error from rain-borne chloride of sodium can afiect 

 our result, surely the limits are fixed with sufficient straitness ! 

 We have, without any further deductions, 96 millions of years if we 

 accept the correction of 10 per cent, on the chloride of sodium of 



