296 DISCUSSION'S IN COSMOLOGY. 



" We must," quoting Sir William's own words on the 

 subject, "allow very wide limits on such an estimate 

 as I have attempted to make ; but I think we may, 

 with much probability, say that the consolidation can- 

 not have taken place less than 20,000,000 years ago, 

 or we should have more underground heat than we 

 actually have, — nor more than 400,000,000 years ago, 

 or we should not have so much as the least observed 

 underground increment of temperature. That is to 

 say, I conclude that Leibnitz's epoch of ' emergence ' of 

 the ' consistentur status' was probably within these 

 dates."* 



* Trans. Roy. Soc. of Edinburgh, vol. xxiii., p. 161. 



