X GEOLOGICAL REFORM 883 



who have made the suggestions I have cited. On 

 the contrary, it is necessary to my argument to 

 assume that they are all correct. But I desire to 

 point out that this seems to be one of the many 

 cases in which the admitted accuracy of mathe- 

 matical process 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 upon 

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

 world will not extract wheat-flour from peascods, 

 so pages of formulae will not get a definite result 

 out of loose data. 



In the present instance it appears to be 

 admitted : — 



1. That it is not absolutely certain, after all, 

 whether the moon's mean motion is underofoinof 

 acceleration, or the earth's rotation retardation.^ 

 And yet this is the key of the whole position. 



2. If the rapidity of the earth's rotation is 

 diminishing, it is not certain how much of that 

 retardation is due to tidal friction, how much to 

 meteors, — how much to possible excess of melting 

 over accumulation of polar ice, during the period 

 covered by observation, which amounts, at the 

 outside, to not more than 2,600 years. 



^ It will be understood that I do not wish to deny that the 

 earth's rotation may he undergoing retardation. 



