JOHN WESLEY POWELL II5 



part are of that fallacious order which we call speculation. 

 True explanations are discovered, as a rule, by master work- 

 men who have trained themselves by long apprenticeship in the 

 fundamental work of observation. 



The motive which actuates men of science in all this work is 

 the increase of knowledge, but the results of their labor go far 

 beyond increase of knowledge, for they include also increase 

 of welfare. There is a large group of men, not necessarily 

 nor usually students of pure science, whose special function it 

 is to discover ways of applying scientific knowledge to the 

 benefit of mankind. Collectively we call the labors and achieve- 

 ments of these men applied science. 



Powell's work in geology included observation, classification, 

 explanation, and application to welfare. 



His work as an observer began in early manhood, while he 

 was a teacher and afterward a college professor. It ranged 

 through various departments of zoology and botany as well as 

 geology and paleontology, and was carried on in the Missis- 

 sippi Valley, on the Great Plains, and in the Rocky Mountains. 

 It gave him a wide familiarity with the phenomena of Nature, 

 and was of great educational value, but it made no printed 

 record. Afterward he made systematic surveys of the geology 

 of two western districts, one traversed by the Green River and 

 the other by the Colorado, and the results of these surveys were 

 committed to writing and given to the public. 



In the second division of geologic work his chief contribu- 

 tions are three in number : A classification of mountains, a 

 classification of processes of land sculpture, and a classification 

 of stream valleys. While these classifications were not founded 

 on principles of causation, and can not therefore be assumed to 

 be final, it is proper to say that each one was characterized by 

 originality, marking a distinct advance on previous classifica- 

 tions ; each one has had a distinct influence on the trend of 

 geologic thought ; and the elements of each, after nearly three 

 decades of phenomenal development of science, are to be 

 found in all modern text books of geology. 



His contributions to explanatory geology pertain likewise to 

 mountains, land sculpture, and stream valleys. He advanced a 



