340 THE GEOLOGIC ATLAS OF THE UNITED STATES 



States is found in the development of geographic problems and 

 results. In earlier decades the geographic work was exploratory, 

 and bent toward the discovery and conquest of unknown or little- 

 known territory. As time passed, more and more attention was 

 given to the resources of the newly discovered valleys and plains, 

 mountains and forests ; and, now that the exploration of our ter- 

 ritory is complete, the efforts of the pioneers are devoted to dis- 

 covery of new resources. This change in purpose, albeit gradual, 

 cannot be too strongly impressed. The earlier work was areal 

 and largely limited to the surveys of the land, the present work 

 has a vertical element reaching toward the resources of the rocks 

 below and the powers of the air and vapor above ; the earlier 

 studies related to materials, the present investigations relate to 

 natural powers and potentialities — in brief, the one sought to 

 subjugate matter, the other seeks to make conquest of force. 

 Various instrumentalities of national character have contributed 

 toward this transformation in beneficent activity, but none have 

 contributed more, esjDecially during the last dozen years, than 

 the U. S. Geological Survey. 



During the earlier years of its existence the Geological Survey 

 devoted chief attention to topographic surveying and mapping, 

 the maps being designed for subsequent use by the geologist; 

 and the bureau came to be known favorably throughout the 

 country and the world by reason of the extent and excellence of 

 the topographic maps. During this period a corps of geologists 

 were employed in researches designed partly for the develop- 

 ment of a system of classification adapted to the subsequent 

 geologic mapping. The two branches of the work were judi- 

 ciously coordinated by Director Powell, so that when the topo- 

 graphic surveys were sufficiently advanced in different districts 

 the geologists were provided with adequate classific systems, and 

 were able to proceed at once to effective geologic work ; and 

 this coordination has been continued by Director Walcott with 

 the normal increase in production of geologic maps. 



The plan of publication adopted by the Survey marks an 

 epoch in the history of practical scientific work ; for it is de- 

 signed to bring the results of the most advanced scientific re- 

 search within the reach of every citizen of the nation, and within 

 the mental grasp of every graduate from the public schools of 

 America; the plan represents more fully than any hitherto de- 

 vised in any country the idea of distributing broadcast among 

 the people the rich boon of scientific knowledge. Only a gene- 



