2o 4 GEOLOGICAL TIME 



attempt was made by him to measure that antiquity 

 by any of the chronological standards of human con- 

 trivance. He was content to realise for himself and 

 to impress upon others that the history of the earth 

 could not be understood, save by the admission that 

 it occupied prolonged though indeterminate ages in its 

 accomplishment. And assuredly no part of his teach- 

 ing has been more amply sustained by the subsequent 

 progress of research. 



Play fair, from whose admirable Illustrations of the 

 Huttonian Theory most geologists have derived all 

 that they know directly of that theory, went a little 

 further than his friend and master in dealing with the 

 age of the earth. Not restricting himself, as Hutton 

 did, to the testimony of the rocks, which showed neither 

 vestige of a beginning nor prospect of an end, he called 

 in the evidence of the cosmos outside the limits of our 

 planet, and declared that in the firmament also no 

 mark could be discovered of the commencement or 

 termination of the present order, no symptom of in- 

 fancy or old age, nor any sign by which the future or 

 past duration of the universe might be estimated. 1 He 

 thus advanced beyond the strictly geological basis of 

 reasoning, and committed himself to statements which, 

 like some made also by Hutton, seem to have been 

 suggested by certain deductions of the French mathe- 

 maticians of his day regarding the stability of the 

 planetary motions. His statements have been dis- 

 proved by modern physics ; distinct evidence, both 

 from the earth and the cosmos, has been brought 

 forward of progress from a beginning which can be 



1 Illustrations of the Huttonian Theory, § 1 1 8. 



