244 ^ag J5n k m0ns, ssags, antr JUbiefes. [xi. 



tinguished physicist takes to be the representative of 

 geological speculation in general. And thus a first 

 issue is raised, inasmuch as many persons (and those 

 not the least thoughtful among the younger geologists) 

 do not accept strict Uniformitarianism as the final form 

 of geological speculation. We should say, if Huttoy 

 and Playfair declare the course of the world to have 

 been always the same, point out the fallacy by all means ; 

 but, in so doing, do not imagine that you are proving 

 modern geology to be in opposition to natural phi- 

 losophy. I do not suppose that, at the present day 

 any geologist would be found to maintain absolute 

 Uniformitarianism, to deny that the rapidity of the 

 rotation of the earth may be diminishing, that the sun 

 may be waxing dim, or that the earth itself may be 

 cooling. Most of us, I suspect, are Gallios, " who care 

 for none of these things/' being of opinion that, true 

 or fictitious, they have made no practical difference to 

 the earth, during the period of which a record is pre- 

 served in stratified deposits. 



The accusation that we have been running counter to 

 the principles of natural philosophy, therefore, is devoid 

 of foundation. The only question which can arise is 

 whether we have, or have not, been tacitly making 

 assumptions which are in opposition to certain con- 

 clusions which may be drawn from those principles. 

 And this question subdivides itself into two : the first, 

 are we really contravening such conclusions ? the second, 

 if we are, are those conclusions so firmly based that we 

 may not contravene them ? I reply in the negative to 

 both these questions, and I will give you my reasons 

 for so doing. Sir William Thomson believes that he 

 is able to prove, by physical reasonings, "that the 

 existing state of things on the earth, life on the earth 

 all geological history showing continuity of life 



