566 



REPOET OF NATIONAL MUSEUM, 1904. 



Up to 1880 live reports of progress were issued, dealing mainly with 

 economic problems. 



The plateau country drained by the Colorado River offers facilities 



for the study of geological problems such as are, perhaps, equaled 



nowhere else in the world. This is especially true with reference to 



problems relating to stratigraphic succession, of uplift 



Powell's Exploration L .. *> . . » , \ , 



of the Grand Canyon, with a minimum amount of contortion of the beds, and 



1869=1874. „ . _. , 



of erosion. Ihe plateau nature of the country was 

 recognized by Newberry while with the Ives expedition in 1860, and 

 by Blake in connection with the Pacific Railroad surveys in 1850. It 

 remained, however, for Powell, Gilbert, and Dutton to first bring out 

 the salient features of the geology of the region and to work out the 

 problems in a way that, to quote the words of Emmons", has formed 

 the starting point of modern physical geography. 



In the summer of 1869, J. W. Powell, a retired officer of the Federal 



Army, made a boat trip clown the Colorado, 

 starting from Green River City on the Union 

 Pacific Railroad May 24, and emerging from 

 the mouth of the Black Canyon, nearly 900 

 miles below, on August 30 following — a 

 journey that, to quote Emmons again, '•'is 

 unequaled in the annals of geographical 

 exploration for the courage and daring dis- 

 played in its execution." 



In his reports on these explorations, b 

 which were made and published under direc- 

 tion of the Smithsonian Institution, Powell 

 called attention to the fact that the canyons 

 are gorges of corrosion and due to the action 

 of the river upon the rocks, which were 

 undergoing a gradual elevation. As he expressed it, the river pre- 

 served its level, but the mountains were lifted up; as the saw revolves 

 on a fixed pivot while the log through which it cuts is moved along. 

 The river was the saw which cut the mountain in two. This is essen- 

 tial^ the idea advanced by Ha} T den in 1872 in his report on the geology 

 of Montana. 



In this report Powell first made use of the expressions of antecedent 

 and consequent valleys, meaning in the first instance that the drainage 

 was established prior or antecedent to the corrugation of the beds by 

 faulting and folding; and in the second case, that the valleys have 

 directions which are dependent upon the corrugations. Valleys which 

 were formed by streams, the present courses of which were deter- 



a Presidential address, Geological Society of Washington, 1896. 

 b Letter of transmittal dated June 16, 1874; publication in 1875. 



lolm UVsk'V I'owell. 



