AN ESTtMATE OF THE GEOLOGICAL AGE OF THE EARTH. 261 



igneous constituents of the earth's crust, li per cent of the chlorine 

 fixed in the salts brought into solution would be united with sodium. 

 This we now find will amount to 3,049X10^^ tons combining with 

 1,972 X 10^^ tons of sodium. But we have already seen that to-day there 

 are 15,627x10^"' tons of sodium in the ocean. The correction is 12.6 

 per cent. This on the period of 99.4x10" years 18 12.5X10" years 

 nearly, which is evidently a subtractive correction and reduces the 

 estimate of geological time to 86.9x10" years. 



This correction is based on the view that the chlorine now in the 

 ocean, or nearh" this amount, must originally have been free in the 

 atmosphere and hydrosphere. This is assumed as the only alternative 

 open to us in disposing of this substance. Previous writers have 

 accepted this view. If free, it can hardly have been otherwise com- 

 bined than with hydrogen. The dissociating temperature of HCl is 

 some 500"- above that of water; hence the chlorine would have taken its 

 hydrogen befoi'e the formation of water was possible. 



Sterry Hunt has further assumed that sulphur, in the form of acid 

 gas, entered into the composition of the primeval atmosphere. The 

 early high temperature condition would result in " the conversion of 

 all carbonates, chlorides, and sulphates into silicates, and the separa- 

 tion of the carbon, chlorine, and sulphur in the form of acid gases, 

 which, with nitrogen, watery vapor, and a probable excess of oxygen, 

 would form the dense primeval atmosphere."^ 



That sulphuric acid existed in the early atmosphere and hydrosphere 

 in at least relatively small quantities, is more than probable. In the sea- 

 salts of to-day it forms a relatively small part, and is being supplied by 

 the rivers at a rate which, acting over geological time, is far more than 

 sufficient to account for all that is in it.^ It is being constantly thrown 

 down upon the ocean floor in the form of calcium sulphate, constituting 

 about 0.7 per cent of the red clay, and 0.4 per cent of the radiolarian 

 ooze, 0.3 per cent of the diatom ooze, and about 0.8 per cent of the 

 globigerina ooze, as well as entering into other extensive floor deposits 

 of the ocean. Sulphur exists, according to Clarke, as a constituent 

 of the fundamental crust, amounting to 0.06 per cent. We find, then, 

 not only a source of supply in the rocks, but an annual river supply 

 more than adequate to account for what is in the ocean. We can not, 

 therefore, fairly make allowance for its solvent action in early times. 

 If free, it probabh^ existed in relatively minute quantities. 



In the case of carbonic acid we can effect a faiily satisfactory estimate 

 of its n jount from the volume of limestone rocks now on the earth's 

 surfac j; but in the case of this acid we find a much less energetic body 



' Chemical and Geological Essays, 1897, p. 40. 



^ The annual river supply of the element sulphur is about 124X10^ tons, and the 

 mass of S in the ocean is about 12x10'^ tons. A part of the sulphates of the rivers 

 is derived from rain, and hence from the sea. 



