AMERICAN EXPLORATION TRIBUTE. 97 



soil marched side by side with the study of its topography and 

 relief. This important mission was placed, in 1872, under the 

 direction of Lieutenant Wheeler, who in the preceding year had 

 explored a portion of Nevada and Arizona. The choice could not 

 have been better, as is proved by the career since then of the dis- 

 tinguished engineer. His purpose was to reconnoitre the natu- 

 ral resources of the mountainous country in the neighborhood of 

 the chosen parallel, and also of the great railroad lines of the 

 Union and Central Pacific between the one hundred and fourth 

 and one hundred and twentieth degrees of longitude west from 

 Greenwich. After having examined the Sierra Nevada and the 

 Coast Ranges, Prof. Whitney, Director of the Geological Survey 

 of California, pushed his investigations toward the Pacific slope. 

 But, between California on the west and the base of the Rocky 

 Mountains on the east, exploited by Hayden, there remained a 

 vast gap of sixteen degrees of longitude which was little known. 

 Under the direction of Mr. Clarence King this gap was very well 

 filled. A general knowledge was acquired of the great mountain 

 system of North America and that in its greatest expansion. We 

 possess now results sufficient to make clear the important problem 

 of the dynamics of mountain chains. 



Since 1879 all the geological studies executed at the expense of 

 the central Government have been confided to a single adminis- 

 tration bearing the title of the Geological Survey. 



Organized by Clarence King, it passed in the following year 

 under the direction of J. W. Powell, in whose able hands it has 

 since remained. Its end, as is defined by the organic law, is the 

 reconnoissance of the geological structure of the country, of its 

 mineral resources, and finally the execution of a geologic map. 



The researches carried forward in very different directions of 

 science have been apportioned to many divisions: Geography, 

 geology, paleontology, and others. Geologists, to the number of 

 about twenty, are each one charged with special functions, and 

 their results are gathered each year into a report of the director 

 under the name of Annual Report. It is a large volume pub- 

 lished in magnificent shape, in which are likewise collected mem- 

 oirs upon divers subjects, with an accompaniment of numerous 

 maps, engravings, and photolithographs. Already ten annual 

 reports have appeared. 



Besides these reports the survey has published from time to 

 time monographs upon subjects particularly interesting, likewise 

 under the form of very beautiful volumes, accompanied with 

 many figures, and occasionally by a voluminous atlas. 



Also under the title of bulletins, of which already have ap- 

 peared sixty papers relating to subjects new and interesting. And, 

 finally, a statistical publication bearing the name of Mineral 



VOL. XLIII. 8 



