48 



SCIENCE. 



[N. S. Vol. V. No. 106. 



and striking features of its geology. In 

 1873 and '74 Powell himself, assisted by 

 Dr. C. A. White, extended the geological 

 observations made along the banks of the 

 upper Green River into the surrounding 

 country, and in 1876 published his report 

 upon the geology of the eastern Uinta 

 Mountains. 



Under this organization also Mr. Gilbert 

 made, in the summer of 1775, his classic 

 study of the Henry Mountains, the most 

 prominent among the laccolitic groups that 

 project above the Colorado Plateau, and in- 

 troduced for the first time the term laccolite 

 into geological literature. This effectually 

 refuted Scrope's dictum, which at one time 

 was almost an axiom among Europe geol- 

 ogists, that igneous eruptions do not exert 

 any elevatory force upon the surrounding 

 sedimentary beds through which they have 

 been extruded. 



The final work of the Powell Survey was 

 the study, in 1875-6 and 7, of the High 

 plateaus of Utah by Captain C. E. Button, 

 an officer of the Ordinance Corps of the 

 United States, on detached duty ; he also 

 made the petrographical examination of the 

 igneous rocks brought in by Gilbert from 

 the Henrj' Mountains. To this report, which 

 was published in 1880, there was appended 

 a prefatory note by Major Powell, giving a 

 general sketch of the orographic movements 

 recorded by him during his investigations 

 in the Plateau region. 



Wlieeler Survey. I have reserved my men- 

 tion of the work of the Wheeler Survey to 

 the last, although chronologicallj'^ its geo- 

 logical work antedates much that has al- 

 ready been mentioned, for the reason that 

 as an organization, as indicated by its title 

 (United States Geographical Surveys West 

 of the 100th Meridian) , it did not recognize 

 geology as an essential part of its work. 



The Wheeler Survey was indirectly an 

 outcome of the 40th Parellel. When two 

 seasons' campaigning of the latter organiza- 



tion had proved the practical feasibility of 

 conducting such work in the Western moun- 

 tains. Lieutenant G. M. Wheeler, of the 

 United States Engineers, secured the con- 

 sent of his chief to undertake, in the sum- 

 mer of 1869, a military reconnaissance for 

 topographical purposes in southwest Nevada 

 and western Utah. Although no geologist 

 was attached to this first expedition, visits 

 were made to various mining districts, but 

 the reports thereon, like the ordinary min- 

 ing reports of the time, were of little or no 

 geological value. From this gradually 

 grew up an important organization sup- 

 ported by direct appropriations from Con- 

 gress, which contemplated the making of a 

 topographical map of the whole area of the 

 United States west of the 100th meridian, 

 and which in point of numbers finally far 

 exceeded any of the other organizations. 



Its work was carried on continuously 

 from 1871 to 1879, and produced a large 

 number of topographical maps of the west- 

 ern countrj', a few of which were afterwards 

 colored geologically. 



Wheeler did not approve of the system 

 of topographical survey adopted by the 40th 

 Parallel and subsequent surveys, but con- 

 ducted his work after the manner of earlier 

 military expeditious, by making meander 

 lines along the valleys, instead of triangula- 

 tions from the summits of the ridges, the 

 principal basis of his details of topograph- 

 ical structure. His maps, morever, were 

 drawn in hachures instead of in contour 

 lines. 



In spite of the somewhat discouraging- 

 peculiarities of organization, the geological 

 work done under this survey reached a 

 high standard of excellence, owing to the 

 ability of the men to whom it was entrusted. 

 First among these was Gilbert, who as chief 

 geologist, worked in the Great Basin of Ne- 

 vada, in eastern California and southwestern 

 Utah in the summers of 1871 and '72, visit- 

 ing the plateau region around the mouth of 



