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GEOLOGICAL SURVEY OF THE UNITED STATES. 



it, or with that of the various State geological 

 surveys. Its moderate amount is to be ascribed 

 partly to the fact that the early years of a 

 survey necessarily witness the inception of 

 numerous researches and the completion of 

 comparatively few; but chiefly to the policy 

 adopted by the director of affording publica- 

 tion only to material that has been so thor- 

 oughly assorted and elaborated that its orderly 

 presentation is economic of the time and pa- 

 tience of the reader. It is believed that the 

 double advantage of enhanced quality and re- 

 stricted quantity outweighs the disadvantage 

 of delay. 



Relations to State Surreys. Although geologic 

 surveys have existed in most civilized coun- 

 tries for many years, our own can not be said 

 to have been modeled after any other. Its 

 organization has been developed under the 

 influence of American institutions and Ameri- 

 can needs, and has a peculiar and distinctive 

 character. This is well illustrated by com- 

 paring it with the geologic survey of Great 

 Britain. In that country an elaborate survey 

 for the making of detailed topographic maps 

 was instituted many years ago, before geology 

 had fairly taken her place among the sciences; 

 and when the mapping of the geologic forma- 

 tions was afterward undertaken by the Gov- 

 ernment, the geologic corps, being already fur- 

 nished with topographic maps, had no need of a 

 geographic division. The task to which it ap- 

 plied itself was the tracing of the outcrops of 

 the various formations across the surface of the 

 country, and their accurate delineation upon 

 maps furnished by the Ordnance Survey. Along 

 with the tracing there is carried minute ob- 

 servation of the nature of the formations and 

 of their dips and strikes, and thus has been 

 accumulated the basis for the broadest gen- 

 eralizations. But these generalizations the 

 official organization refrains for the most part 

 from drawing, leaving that work to private 

 geologists, or to official geologists in their pri- 

 vate capacity. While it may fairly be said 

 that England has contributed more than any 

 other country to the philosophy of the science, 

 her governmental publications are almost re- 

 stricted to its dry facts. In the United States, 

 the lack of good maps, while it has led the 

 geologic organization to undertake the mak- 

 ing of them, has at the same time prevented it 

 from devoting its energies to the elaborate 

 tracing of outcrops, and induced it to under- 

 take the discussion of broader problems in- 

 volving theoretic considerations of the highest 

 order. A similar tendency arises from the re- 

 lations of the States to the General Govern- 

 ment. In Great Britain there are no institutions 

 like our State surveys, and the Government 

 assumes the investigation of local geology. In 

 this country important work has been done by 

 many individual States, and in several instances 

 the geographic distribution of the formations 

 has been determined as accurately as existing 

 maps permitted. Inasmuch as such work is 



of prime importance to all economic interests 

 based on mineral resources, and as such econom- 

 ic interests are local, it is believed that it can 

 be conducted most advantageously by State 

 surveys. An ideal system would distribute 

 governmental investigation in a manner strict- 

 ly parallel to the distribution of governmental 

 control. An organization in each State would 

 assume the study of all local details, and of all 

 economic matters of purely local importance, 

 and the general organization would take cog- 

 nizance only of general questions involving 

 larger areas than States. 



While the poverty of some States, the indif- 

 ference of others, and the existence of large 

 areas without State organization will prevent 

 the full realization of such a system, there is a 

 distinct tendency in that direction. A mutual 

 adjustment has been effected between the work 

 of the general survey and that of several State 

 surveys so as to avoid duplication, and in most 

 cases the partition of work has been accom- 

 panied by an arrangement for co-operation. 

 In Massachusetts there is co-operation in topo- 

 graphic work, the United States Geological 

 Survey undertaking to map the entire State 

 on the maximum scale of 1 : 62,500, or one 

 mile to the inch, on condition that the State 

 defrays one half of the expense ; and in New 

 Jersey a somewhat similar arrangement has 

 been made. 



Investigation of the Drift. To illustrate the dis- 

 tinctively general nature of the national sur- 

 vey, a brief outline will be given of its investi- 

 gation of the drift. Throughout a great portion 

 of the northern United States the surface is 

 largely constituted of loose materials, collect- 

 ively known as u the drift." This formation 

 differs in essential particulars from the residu- 

 ary and alluvial deposits that constitute the 

 greater part of the incoherent debris distribut- 

 ed over the surface of the land. As rocks 

 are disintegrated and partially dissolved by 

 rain and other atmospheric agencies, the clay, 

 sand, and blocks that remain are called residu- 

 ary. A portion of this residuary material is 

 washed into streams, and by them is trans- 

 ported to valleys, where it is redeposited, and 

 it is then called alluvium. The blocks belong- 

 ing to a residuary deposit are either angular or 

 else exhibit on their surfaces incipient decay. 

 The blocks or bowlders of the drift are all 

 abraded and more or less rounded, and are 

 usually homogeneous. Eesiduary clays, hav- 

 ing been produced by leaching, contain no 

 soluble minerals ; the clays of the drift ordi- 

 narily abound in the carbonates of lime and 

 magnesia. Alluvium is more or less assort- 

 ed, fine and coarse matter being deposited at 

 different places, or, if at the. same place, at 

 different times and in separate strata ; much of 

 the drift is unassorted, beds of the finest clay 

 containing not only pebbles but bowlders of 

 great size. Kesiduary deposits lie on the rocks 

 from which they are derived. Alluvium lies at 

 lower levels than the parent rock, and its 



