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 distinguished engineer. His purpose was to reconnoitre the natural 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 administration 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 published in magnificent shape, in which are likewise collected memoirs 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 appeared sixty papers relating to subjects new and interesting. And, finally, a statistical publication bearing the name of Mineral
