24 THE AGE OF THE EARTH 



We may next take the evidence of the stratified rocks. 

 Their total maximum thickness is, as we have seen, 

 265,000 feet, and consequently if they accumulated at 

 the rate of one foot in a century, as evidence seems to 

 suggest, more than twenty-six millions of years must 

 have elapsed during their formation.* 



Before discussing the validity of the argument on 

 which this last result depends, let us consider how far it 

 harmonises with previous ones. It is consistent with 

 Lord Kelvin's and Professor Darwin's, but how does it 

 accord with Professor Joly's ? Supposing we reduce his 

 estimate to fifty-five millions : what was the earth doing 

 during the interval between the period of fifty-five millions 

 of years ago and that of about twenty-six millions, 

 when, it is presumed, sedimentary rocks commenced to 

 be formed ? Hitherto we have been able to reason on 

 probabilities ; now we enter the dreary regions of possi- 

 bilities, and open that obscure chapter in the history of 

 the earth previously hinted at. For there are many 

 possible answers to this question. In the first place the 

 evidence of the stratified rocks may have been wrongly 

 interpreted, and two or three times the amount of time we 

 have demanded may have been consumed in their for- 

 mation. This is a very obvious possibility, yet again 

 our estimate concerning these rocks may be correct, but 

 we may have erroneously omitted to take into account 

 certain portions of the Archaean complex, which may 

 represent primitive sedimentary rocks, formed under 

 exceptional conditions, and subsequently transformed 

 under the influence of the internal heat of the earth. 



This, I think, would be Professor Bonney's view. 



Finally, Lord Kelvin has argued that the life of the sun 



as a luminous star is even more briefly limited than that 



of our oceans. In such a case, if our oceans were formed 



* See Note on Radium, p. 63. 



