102 POPULAR LECTURES AND ADDRESSES. 



by it. The one question relevant tc atmospheric 

 effect on the secular cooling of the earth is, what 

 has been the resulting temperature of the upper 

 surface of land and sea ? My calculations depend 

 only on the assumption that through geological 

 history this temperature has been suitable for such 

 life as now exists on the earth. 



21. Criticising the calculations I had adduced 

 regarding the earth's rotation, Professor Huxley 

 makes the following remarks, which have equal 

 bearing upon those regarding the sun's heat and 

 light and the earth's interior temperature : " I desire 

 " to point out that this seems to be one of the 

 " many cases in which the admitted accuracy of 

 " mathematical processes is allowed to throw a 

 " wholly inadmissible appearance of authority over 

 " the results obtained by them. Mathematics may 

 " be compared to a mill of exquisite workmanship 

 " which grinds you stuff of any degree of fineness ; 

 " but, nevertheless, what you get out depends on 

 " what you put in ; and as the grandest mill in the 

 " world will not extract wheat flour from peascocls, 

 " so pages of formula: will not get a definite result 



