THE PROBLEMS OF GEOLOGY 535 



present a third important point of view which interlocks with and 

 overlaps the treatment of geology from the points of view of energy 

 and agent. 



So complex is the earth that to enable the mind to comprehend 

 the intricately interlocking whole, the subject should be considered 

 from as many points of view as possible. If only the human mind 

 were sufficiently powerful, and means of expression adequate, the 

 ideal method of treatment would be simultaneous consideration and 

 exposition of all possible points of view. But since this method of 

 treatment is an impossibility, we must necessarily at any time con- 

 sider each portion of the subject in part and treat it in part. The 

 problem is then the selection of the various partial points of view 

 which are important, and the determination of the order of their 

 consideration. 



No one, I think, can hold that any of the points of view above 

 mentioned process, energy, agent, and result is unimportant in 

 a general treatment of the subject of geology. It is therefore clear 

 that all these points of view must be handled. There may be differ- 

 ence of opinion as to the order in which they shall be presented; and 

 for different parts of the subject of geology and for different purposes 

 the best order will vary. 



We are now in a position to foresee the future development of 

 the science of geology. The early papers and text-books were con- 

 tent to tell of accomplished results. Almost nothing was said with 

 reference to processes. As the science developed, there crept into 

 the literature of the subject more and more reference to processes. 

 The present year a text-book of geology by Chamberlin and Salis- 

 bury has appeared, the first which avowedly attempts to treat geo- 

 logy from the point of view of processes rather than phenomena. 1 

 This is a great step in advance. But a large part of the task of 

 reducing the processes to order in terms of energies, agents, and 

 results still remains to be done. When this is accomplished, we shall 

 have a statement of the principles of geology in terms of physics and 

 chemistry. 



How knowledge of processes has developed. The principles of 

 geology have been developed in the past and will continue to be 

 developed in the future both from the study of processes now in 

 operation and by the consideration of the results of processes which 

 cannot be observed. An excellent illustration of a branch of geology, 

 the principles of which have largely been established by the observa- 

 tion of processes now in operation, is furnished by physiography. 

 So far as one can see, the surface of the land is now being modified 

 by the energies and agents of geology as rapidly as at any time in the 

 past. These energies and agents may have varied in their efficiency 



1 Chamberlin and Salisbury, Geology, vol. i, Processes and their Results, 1904. 



