u7G llEPORT — 1900. 



with hydrogen. The resulting acid wc assume as probably contained in 

 the original atmosphere and hydrosphere. A primitive accelerated 

 denudation can be computed on the basis of the probable mass of chloride 

 of hydrogen and the nature of the lithosphere exposed to attack. The 

 effects concern the present method only so far as they result in supplying 

 sodium to the ocean. 



The maximum amount of chlorine available as an acid basis may be 

 derived from the chlorine now in the ocean less what was supplied during 

 geological time by solution of the rocks. 



Referring to Sir John Murray's table/ we deduce from the amounts 

 of chlorides supplied annually by river discharge '•^ (applying the deduction 

 of 10 per cent, before mentioned to the sodium chloride) that the rivers 

 contribute annually 75-5 x 10^ tonnes of chlorine. If now our final esti- 

 mate of the earth's age is 0-5 x 1 O*" years, the total supply by denudation 

 lias been 7169 x 10^ tonnes of chlorine. 



The total mass of chlorine now in the ocean, calculated on Professor 

 Dittmar's table and the more recent estimate of the mass of the ocean 

 (ante) less the amount calculated as above as supplied by tlie rivers sub- 

 sequently, is 21,123 X 10'- tonnes.-* This amount we assume free to act 

 as a primeval denuding agent. 



According to Mr. F. W. Clarke ■* the older crust of the earth contained 

 the following atomic ^percentages, which would be converted to chlorides 

 by a primeval denudation such as we assume : — 



Dividing among these the mass of chlorine already estimated, we find that 

 the chlorine taken up by the sodium would be 6"7 per cent, of the whole. 

 This would amount to 1415 x 10'^ tonnes, bringing 916-7 X 10- tonnes of 

 sodium into the primeval ocean. 



Deducting this amount from the mass of sodium now in the ocean 

 leaves 14,694 x 10'^ tonnes to be accounted for by subsequent denuda- 

 tion. 



Of the other acid-forming substances possibly present in the primeval 

 atmosjDhere and ocean, sulphur and carbonic anhydride need alone be 

 referred to. The sulphur was, however, probably only free in small 

 amount, if at all, being present in the average igneous crust "' to the 

 extent of 0'06 per cent., and being to-day supplied by denudation in 

 (|uantities more than sufficient to account for all in the ocean. Con- 

 sidering that subdivision of its effects among the metals must also occur, 

 an allowance is not called for. 



Carbonic acid is a relatively feeble and slow rock solvent. Even if 



' Znc. cit. 



" As follows in tonnes per cubic kilometre : — 



NaCl 40G1 



NH.Cl 251 



LiCl 600 



" The chlorides now in the ocean are ; — 



NaCl . . . 39,703 x 10'- tonnes 



MgCl. 6CI2x ICnonnes 



* Biillctiii, U.S. Geological Survey, 148, p. 13. ■' Clarke, loc. cit. 



