GEOGRAPHICAL RESEARCH IN THE UNITED STATES 289 



the Detroit meetino; of the American Association for the Advance- 

 ment of Science by Mr G. K. Gilbert, of the U. S. Geological 

 Survey. 



Another noteworthy geographic Avork by the U. S. Engineers 

 was a general map-making survey in the far west under the di- 

 rection of Capt. George M. Wheeler, U. S. E., and usually referred 

 to as the Wheeler survey. A considerable tract of country was 

 mapped by it on a scale of 8 miles to 1 inch. This survey wnth 

 two others, the so-called Hay den and Powell surveys, were merged 

 in the present Geological Survey in 1879. 



The work of improving rivers and harbors in the interest of 

 commerce is now carried on by the United States engineers, and 

 their geographic work consists in special surveys for these im- 

 provements and of a new survey of the Great Lakes. 



Geological Survey. — The chief agency for increasing geographic 

 knowledge of the United States at the present time is the United 

 States Geological Survey, now eighteen years old. Nearly or 

 quite one-half of its energies and funds are expended in the pro- 

 duction of topographic maps, and thus it is in fact, though not 

 in name, the United States Topographic and Geologic Survey. 

 The conditions confronting this survey at its creation differed 

 in one important particular from those similarly confronting 

 European geological surveys. Those surveys had, in almost if 

 not quite ever}^ case, been preceded by topographic surveys, and 

 the geologists found maps, adequate to their needs, ready made. 

 But in the United States topographic maps were not available, 

 as there had been no topographic survey. Thus progress in geo- 

 logic mapping was impeded at the outset by the lack of suitable 

 maps. Accordingly in 1882 authority was given to make topo- 

 graphic maps, and since then about one-half of the energies of 

 the Survey have been given to their production. Since 1882 the 

 Survey has surveyed and mapped on scales of one, two, and four 

 miles to the inch an area of 760,000 square miles, almost equal 

 to the combined areas of Great Britain, France, Germany, Spain, 

 and Portugal. The results are contained on 980 atlas sheets, 460 

 on the one-mile scale, 460 on the two-mile scale, and 60 on the 

 four-mile scale. These surveys have been made in nearly every 

 state and territory. Following these came the geological sur- 

 veys. But before much progress was possible a large amount of 

 preliminary investigation was needful to determine the great 

 features whose details were to be wrought out and mapped. A 

 system of rock classification uniformly applicable to so great and 



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