XXVI.] THE RATE OF VARIATION. 349 



NOTE. 



I FIND that, taking Sir William Thomson as my authority, I 

 have greatly understated the argument of the foregoing chapter. 

 I quote the concluding paragraph of his paper on Geological 

 Time, in the Transactions of the Geological Society of Glasgow, 

 vol. iii. : — 



" When finally we consider underground temperature, we 

 find ourselves driven to the conclusion that the existing state 

 of things on the earth, life on the earth, all geological history 

 showing contiuuity of life, must be limited within some such 

 period of past time as one hundred million years." 



END OF VOL. I. 



