53 8 THE POPULAR SCIENCE MONTHLY. 



a term, in our humble opinion, much more probable than the 

 other. 



On another point our two allies (allies in the sense of work- 

 ing at the same subject) are in irreconcilable antagonism. The 

 physicists tell us that uniformity of action in all time is impos- 

 sible, while the uniformitarians say that such a shortening of 

 geological time as would follow on the acceptance of the physical 

 argument is against all geological experience. Not only do these 

 opinions clash, but those also concerning the rigidity of the earth 

 and the thickness of its crust are widely divergent. None of these 

 contentions can, however, be disregarded, for we must all rec- 

 ognize the importance of considering the question from every 

 point of view. The argument in favor of uniformity of action 

 has been put before us with so much skill and ability, and possess- 

 ing as it does the charm of an infallible faith, that uniformitari- 

 anism has become the accepted doctrine of the dominant school of 

 geology. Besides, within certain limits and in certain lights, the 

 arguments of the uniformitarian and of the physicist might hold 

 good that is to say, if we would restrict the deductions of the 

 former to the recent period, and could adopt the propositions of 

 the latter. Our part, however, is to see whether their conclusions 

 agree not with their respective assumptions, but with the geo- 

 logical evidence : for no conclusions can be accepted that do not 

 meet with the full concurrence of all the copartners interested 

 in the result, and without respect for their mutual claims progress 

 is not possible. The geologist must attend to the claims of the 

 physicist, and the physicist ought not to overlook those of the 

 geologist. How then stands the case ? 



With regard to the geological problem, we are told by the uni- 

 formitarians that the forces acting on the surface of the globe 

 have been in all past times the same, both in kind and degree, as 

 those now in operation. On those grounds they have proceeded to 

 estimate, first, the time required for mountain and continental 

 elevation ; secondly, the rate of erosion of the valleys, and of the 

 denudation or lowering of the land. Their conjecture is that our 

 limited experience of two thousand to three thousand years has 

 sufficed to furnish us with instances of all the various vicissitudes 

 and changes that the earth has undergone during the illimitable 

 past a generalization incompatible with what is known of the 

 evolution of the earth, and in contradiction to their own premises. 

 For even geologists who recognize no change admit the original 

 molten state of the globe. This of itself involves, in the cooling 

 of the mass, the intervention of stresses and strains, with all their 

 consequences, which render it inconceivable that there was noth- 

 ing in all those stages of the earth's history beyond what our 

 limited experience has brought us in contact with. 



