1869 GEOLOGICAL REFORM 447 



however, the book, like his other popular works, had 

 a wide sale, and became the forerunner of an immense 

 number of school-books on the subject. 



As President of the Geological Society, he delivered 

 an address (Coll. Ess. viii. 305), at the anniversary 

 meeting, February 19, upon the " Geological Reform " 

 demanded by the considerations advanced by the 

 physicists, as to the age of the earth and the duration 

 of life upon it. From the point of view of biology 

 he was ready to accept the limits suggested, pro- 

 vided that the premisses of Sir William Thomson's l 

 argument were shown to be perfectly reliable; but 

 he pointed out a number of considerations which 

 might profoundly modify the results of the isolated 

 causes adduced ; and uttered a warning against the 

 possible degradation of "a proper reverence for 

 mathematical certainty " into " a superstitious respect 

 for all arguments arrived at by process of mathe- 

 matics." 2 



At the close of the year, as his own period of 

 office came to an end, it was necessary to select a 

 new president of the Geological. He strongly urged 

 Professor (afterwards Sir Joseph) Prestwich to stand, 

 and when the latter consented, a few weeks, by the 

 way, before his marriage was to take place, replied : 



JERMYN STREET, Dec. 16, 1869. 



MY DEAR PRESTWICH Many thanks for your letter. 

 Your consent to become our President for the next period 



1 Now Lord Kelvin. 2 See Coll. Ess. viii. lutrod. p. 8. 



