AMERICAN GEOLOGY SURVEYS UNDER POWELL. 619 



Stevenson devoted considerable attention to a discussion of the geo- 

 logical age of the Colorado lignites, which he regarded (Lesquereux 

 to the contrary, notwithstanding), as Cretaceous. He agreed with 

 J. L. Le Conte in regarding the Rocky Mountains as not the product 

 of one upheaval, nor the several axes wholh T synchronous in origin. 

 The first great epoch of accelerated disturbance in the Rocky Mountain 

 region, resulting in the permanent elevation of the surface, he thought 

 to have been synchronous with that during which the Appalachian 

 chain was completed. Further, that the second epoch of elevation 

 began toward the close of the Triassic. This was followed by a period 

 of subsidence during which the Cretaceous beds were laid down, a 

 third period of uplift marking the close of the Cretaceous. During 

 this latter period volcanic agencies were in a state of intense activity, 

 and a vast sheet of lava, two to three thousand feet in thickness, flowed 

 out over the whole region of the Grand and Gunnison rivers. During 

 the Tertiary period still another elevation took place, sufficient to give 

 the rocks of that age a dip of some 5 degrees. 



In his report of the work for 1879 Stevenson discussed in consider- 

 able detail the relations of the Laramie group, which he regarded as 

 but the upper part of Hayden's Fox Hill group — that is, of very late 

 Cretaceous age. He felt that there was no doubt but that the coal 

 tields of the Galisteo area and of southern Colorado were of precisely 

 the same age as those of northern Colorado and Wyoming. 



THE UNITED STATES GEOLOGICAL AND GEOGRAPHICAL SURVEYS 



UNDER J. W. POWELL. 



J. W. Powell's first observations on the geology of the Uinta Moun- 

 tains were made in 1869, when engaged in his famous exploration of 

 the Grand Canyon, already noted. In 1871, 1874, and 1875 he again 

 Powell's Geology visited the plateau region, the last year being accom- 

 Mo'untains 3 pauied by Dr. C. A. White. The results of these later 



1874-75. years of exploration are given in the quarto mono- 



graph on the Geology of the Eastern Portion of the Uinta Mountains, 

 published in 1876. This comprised, all told, 218 pages, with a large 

 folio atlas. 



The expedition of 1875 and those of the intervening years until 1880 

 were made under the authority of the Department of the Interior, the 

 organization, with Powell as director, being known as the second 

 division of the U. S. Geological and Geographical Survey of the Terri- 

 tories. In 1877 the name was changed to the U. S. Geographical and 

 Geological Survey of the Rocky Mountain Region. 



In none of the early Powell surveys was an attempt made at system- 

 atic areal work. Certain striking and well-exemplified features were 

 selected and made the subject of special monographs. In the work 

 of 1876, above noted, Powell divided the region west of the Great 



