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SCIENCE 



NEW YORK, APRIL 28, U 



THE TOPOGRAPBIC MAPS OF THE UNITED STATES 

 GEOLOGICAL SURVEY. 



BY W. M. DAVIS, HARVARD COLLEGE, CAMBRIDGE, MASS. 



OuE national Geological Survey was charged by Congress with 

 the preparation of a geological map of the United States. As no 

 suitable topographic map existed to serve as the base of geologi- 

 cal coloring, the Director of the Survey proceeded to develop a 

 topographic corps for the purpose of producing a map that should 

 serve his needs. This action has from time to time called forth 

 discussion; as, for example, recently in The American Geologist. 

 Information on the subject from the standpoint of the several 

 scientific governmental bureaus may be found in the "Testi- 

 mony before the Joint Commission of Congress," in 1885. It is 

 not my intention to discuss this subject here, as I have been 

 more interested in the examination of the great geographical 

 product of the Survey, than with the association of geographical 

 work with one bureau of the government or another. The re- 

 cent appearance of the first folio of the " Geologic Atlas of the 

 United States," marking the beginning of a most important 

 national publication, without parallel in magnitude in other coun- 

 tries, makes some account of the topographic maps of the Sur- 

 vey appropriate at the present time. 



The first season of topographic field-work under the re organ- 

 ized survey was in 1882. Previous surveys had done much work 

 in the West; but their styles of publication were discordant. 

 Belts of literal country had been mapped by the Coast Survey ; 

 similar belts along the Great Lakes had been mapped by the Lake 

 Survey; and extensive maps were in progress under the Missis- 

 sippi and Missouri River commissions. The areas covered by 

 these various surveys and by the topographic division of the 

 Geological Survey are indicated in the annual reports of the 

 Director. No duplication of earlier work of acceptable character 

 has been attempted; but the results gained by all the surveys 

 are reduced to a uniform style of publication, on a plan that will 

 in time embrace the entire country. 



Details of the plan adopted for the topogiaphic survey are pre- 

 sented in the annual report of the Director for 1884-85. Our 

 country includes an area of 3,000,000 square miles; hence the 

 need of economy. The elaborate methods applicable in smaller 

 European nations could not be introduced. An astronomical 

 and compiiting division took charge of the determination of fun- 

 damental points, where needed. A triangulation division ex- 

 tended the determination of points from those furnished by the 

 astronomical parties or from previous work by the Coast or other 

 Surveys. The Appalachian triangulation, for example, is illus- 

 trated in the sixth annual report of the Survey. While this trian- 

 gulation suffices for the needs of the proposed maps, it is not of 

 such accuracy as would be required in determining the figure of 

 the earth; being in this respect different from the fundamental 

 triangulations of our Coast Survey and of most foreign countries. 

 The saving of time and money, demanded in the survey of so 

 great an area, required this modification of former methods. 

 Numerous topographical parties were placed in the field to fill in 

 the spaces between the smaller triangles. The jjlane table was 

 employed in many districts ; traverse surveying was adopted 

 elsewhere. Railroad levels have been extensively utilized. Much 

 sketching between established points has been required ; and to 

 any one who carries the published maps into the Held, it will be 

 apparent that the details of topographic form are generalized, 

 and are occasionally incorrectly represented, on account of the 



rapidity with which the work was carried on. It was diflficult 

 at first, as it may be still, to secure the services of a sufficient 

 number of expei-ienced topographers; but their practice in the 

 field has added to their expertness in sketching streams, ridges, 

 and contours. Much effort has been given to their improvement; 

 practical field instruction has been given to the newer men dur- 

 ing the summer months, and voluntary meetings for discussion 

 of methods have been held during the winter in Washington. 



Those who wish to examine the style of work followed in the 

 preparation of various sample sheets, should consult the eighth 

 annual report, in which Mr. Gannett has included several graphic 

 illustrations of the number and distribution of points determined 

 by intersections, or of lines run by traverse. Yet it is manifest 

 that much is left to sketching, and, judging from the amount of 

 country covered by a single party in a season's work, the sketch- 

 ing must often be rapid. 



In common with many others, I wish that the accuracy of the 

 surveys might have been greater; but I presume that all ques- 

 tions of method, scale, style, cost, and equitable distribution of 

 work were duly considered by Major Powell, Director, Mr. Gan- 

 nett, Geographer, and other members of the Survey, and decided 

 as seemed best in view of all controlling circumstances. Not 

 least among these controls is the disposition of Congress to sup- 

 port the work. Judging by the appropriations recently voted, 

 it would take the greater part of a century to survey the country 

 by the more elaborate European methods. Our grandchildren 

 and not ourselves would enjoy the products of the work, and few 

 of us are so unselfish as to be satisfied with so long a postpone- 

 ment. 



As to publication, three scales were at first adopted; 1:63,500; 

 1: 125,000; and 1:250,000; corresponding to about one, two and 

 four miles to the inch. The map sheets were divided according 

 to lines of latitude and longitude, a sheet on the smallest scale 

 covering a " square degree," while four and sixteen sheets of the 

 larger scales are required for the same area. Each sheet is 

 named after its chief town and State; and on the later sheets, the 

 name of the four sheets adjoining it are printed on its sides: the 

 four corner-wise sheets might be to advantage indicated in the 

 same way. According to the scale of the map and the compli- 

 cation of the topography, contours are drawn with vertical in- 

 tervals varying from 10 to 200 feet. Each sheet is printed in 

 three colors, as described in the sixth annual report: black for 

 the artificial features and names, all lettering following a 

 consistent plan ; blue for the hydrography, brown for the con- 

 tours. All the sheets thus far issued are printed very clearly, 

 and as a rule accurately ; the earlier ones by Bien of New York, 

 the latter ones by the Survey itself. 



According to information lately received from Mr. Garmett, 

 the number of sheets completed up to June 30, 1893, is as fol- 

 lows: 395 on scale of 1:63,500; 838 on 1:125,000; and 61 on 

 1 : 350,000 ; making a total of 694. The total area surveyed, but 

 not all engraved, to that date was 547,000 square miles, dis- 

 tributed over forty-two States and Territories. In future, only 

 the inch-to-a mile scale will be employed, and the surveys of the 

 current year are conducted with regard to this new feature of the 

 plan. 



Before speaking of certain sheets of the contoured maps, men- 

 tion should be made of several smaller scale maps of the country 

 as a whole. The most important of these is the nine-sheet map, 

 on a scale of 1 : 3,500,000, with contours for 100, 500, 1000, 1500, 

 2000, and highei- thousands of feet. 



A limited edition of this map has been prepared for office use 

 without the black print of artificial features and names, thus 

 giving desirable prominence to the natural features. This is an 



