528 GEOLOGY 



try. Since physics-chemistry is the science of energy and substance 

 in general, and since geology is the science of the energy and sub- 

 stance of the earth, geology is not simply related to those subjects 

 it rests upon them as its one secure foundation. They are the ele- 

 mentary sciences upon which geology is based; for they are the 

 sciences of all energy and substance of which the object of geological 

 science is an insignificant fraction. 



We have now reached the most fundamental problem of geology, 

 the reduction of the science to order under the principles of physics 

 and chemistry. To a less extent geology is subject to the sciences 

 of astronomy and biology. 1 



While the relations of geology to the other sciences, as above set 

 forth, are incontestable, it was possible to appreciate those relations 

 only after the sciences were well developed. Geology did not begin 

 consciously as the science of the physics and chemistry of the earth. 

 The phenomena of the earth were studied as objects, and thus geology 

 was at first an observational study. The next step, a revolutionary 

 one, was to explain the observed phenomena in terms of physical 

 and chemical processes, many of which could be observed. But few 

 have asked the question: "What is a geological process?" 



Geological Processes 



It is a curious fact that, while the word "process" is used in in- 

 numerable geological papers and text-books, I have been unable to 

 find anywhere a definition of a "geological process." 



I shall define a "geological process" as the action of an agent by 

 the exertion of force involving the expenditure of energy upon some 

 portion of the substance of the earth. 



Physical definitions of "force," "work," energy," and "agent." 

 In order to understand the above definition of "geological process" 



1 The earth is the vastest aggregate of matter within the direct reach of man. 

 By a study of a small part of this aggregate the principles of physics and chemistry 

 have been formulated. The material which has been studied is but an inappre- 

 ciable part of the material of the earth, and but an infinitesimal part of the sub- 

 stance of the universe. Yet the doctrine is unhesitatingly accepted that the prin- 

 ciples of physics and chemistry, wrought out with reference to this minute fraction 

 of substance, are not only applicable to all the materials of the earth, but to all 

 parts of the visible universe. This daring generalization has received astonishing 

 confirmation by studies of other portions of the visible universe through the 

 spectroscope and photographic plate. 



In the generalization that the principles of physics and chemistry, developed 

 by study of small masses of material, apply to all parts of the universe, we have a 

 case of the extension of a generalization from a part to the whole, which surpasses 

 almost any similar extension of reasoning. Indeed, some philosophers have seri- 

 ously questioned the legitimacy of the conclusion. 



In view of the foregoing, it is rather curious that the geologist now finds his 

 most important problem, the problem of problems, in the explanation of phe- 

 nomena exhibited by the heterogeneous earth in terms of those principles of 

 physics and chemistry built up mainly by observation, experiment, and reasoning 

 upon a minute fraction of the earth 



