596 CHARLES R. VAN HISE 



mous quantities of energy, only a small part of which is manifest to 

 the senses, and this only under special circumstances. So far as 

 geological bodies have great stores of energy which are not manifest 

 as force, there is no change of condition — no geological process. 

 The geologist is primarily concerned with the energy which is mani- 

 festing itself either statically or dynamically by the exertion of force. 

 Consequently, he more often refers to the forces of geology than the 

 energies of geology. This is the more natural since the unit of force 

 and the unit of energy are the same, and that energy is measured only 

 by its action as a force. While in the past the primary interest of 

 the geologist has been in force rather than in energy, it is probable 

 that in the future he will become more and more concerned in the 

 energy itself and its sources. 



Often the geologist has made no discrimination between the 

 words "force" and "energy." He has frequently used "force" in 

 the old sense, both to cover the thing itself, the energy, and the 

 action of energy, the force, in accomplishing work. This formerly 

 was the practice of physicists also, who, for instance, spoke both of 

 the conservation of force and the exertion of force. If the conclusion 

 be correct that the source and amount of energy concerned in a process 

 should be discriminated from its action as a force, it is clear that 

 the time has now come when the geologist must in his writing clearly 

 differentiate the two ideas. 



Since the physicist now makes an important discrimination between 

 the words "energy" and "force," it may be necessary for the geolo- 

 gist to follow him in his definitions of these words, although much 

 can be said against technicalizing and narrowing the use of the 

 general term "force." Probably the interests of all the sciences 

 would have been best subserved if the physicists had introduced a 

 new word for the technical sense assigned to the word "force," and 

 had left this term to be used in the general way in which it has been 

 used in the past in science, and will continue indefinitely in the future, 

 to be used in literature. This is especially true since, if we confine 

 the word "force" to its physical definition, we are in constant need 

 of a word to cover both energy and force, as defined by the physi- 

 cists. If the latter word be technicalized, I can think of no better 

 word than "power" for the conception which includes both. This 



