638 JOHN WESLEY POWELL. 



Bet'oi'o turning" to Powcirs direct contrihutions to science, mention 

 should be made of his studies in biolooy. In early manhood he was 

 an assiduous collector of plants, fresh-water shells, and reptiles, and 

 this Avork was accompanied by studies in distribution, l)iit the results 

 of such studies do not constitute a contril)ution to botany and zoology .- 

 The work was properly a part of his education, a training- in tlie art 

 of ol)servation, which bore fruit only when his attention was turned to 

 other branches. 



Tlis contributions to geology include a certain amount of descriptiye 

 work. He pul)lished the stratigraphy, structure, and part of the areal 

 geology of the Colorado plateaus and the Uinta Mountains. In con- 

 nection with the field studies in tliese districts he developed a new 

 classification of mountains, by structure and genesis; a structural clas- 

 sification of dislocations; a classification of valle3^s; and a genetic 

 classification of drainage systems. His classification of drainage 

 recognized three modes of genesis, of Avhich two were new. With 

 the novel ideas involved ii\ the terms "superimposed drainage" and 

 "antecedent drainage" were associated the broadei- idea that the phy- 

 sical histor}' of a region might be read in part from a study of its 

 drainage system in relation to its rock structure. Another broad idea, 

 that since the dc^gradation of the land is limited downward by the level 

 of the standing water which receives its drainage, the types of land 

 sculpture throughout a drainage area are conditioned by this limit, 

 was formulated by means of the word " base level." These two ideas, 

 gradually developed by a younger generation of students, are the f im- 

 damental principles of a new sul)science of geology sometimes called 

 geomorphology, or physiographic geology. 



The scientific study of the arid lands of our AVestern domain in rela- 

 tion to human industries practically began with Powell. Early in his 

 govermuental woi'k he issued a volume on the lands of the arid region, 

 and he continued their discussion in one way or another for twenty' 

 years, setting forth the physical conditions associated with aridit}^, 

 th(^ paroxysmal character of rainfall, th(^ depiMulence of arable low- 

 lands on the rainfall and snowfall of uplands, and the generous 

 response of the vegetation of arid regions to the artificial application 

 of Avater. Emjihasizing the necessity of irrigation to successful agri- 

 culture, he ])olnted out the need of conserving storm waters b}' artifi- 

 cial reservoirs, the need of ap])lying new principles in legislation for 

 the regulation of water rights, and tln^ need of a new system of hiAVS 

 for th(» conti-ol of title in arid lands. These ideas when first advanced 

 were the su1)ject of hostile criticism because they antagonized current 

 opinions as to the availal>ility of our Western domain for settlement; 

 ])ut he afterwards found himself part of a gemu'al movement for the 

 intelligent develo})ment of the West, a movement whose latest achieve- 

 ment is the so-called reclamation law. 



