DESCRIPTION OF THE 



OF THE UNITED 



TOPOGRAPHIC MAP 

 STATES. 



The United States Geological Survey is making 

 a topographic map of the United States. This 

 work has been in progress since 1882, and about 

 one-tifth of the area of the country, including 

 Alaska, has been mapped. The mapped areas 

 are widely scattered, nearly "every State beiu^ 

 represented, as shown on the progress map 

 accompanying each annual report of the Director. 



This great map is being published in atlas 

 sheets of convenient size, which are bounded by 

 parallels and meridians. The four-cornered divi- 

 sion of land corresponding to an atlas sheet is 

 called a qiiadrangle (a word used as specifically 

 as section is in the surveys of the public lands). 

 The sheets are of approximately the same size: 

 the paper dimensions are 21|- by 18|- inches; the 

 map occupies about 11 \ inches of height and 11^ 

 to 16 inches of width, the latter varying with 

 latitude. Three scales, however, are employed. 

 The largest scale is 1:62,500, or very nearly one 

 mile to one inch; i. e., one linear mile on the 

 ground is represented by one linear inch on the 

 map. This scale is used for the thickly settled 

 or industrially important parts of the country. 

 For the greater part of the country an inter- 

 mediate scale of 1:125,000, or about two miles to 

 one inch, is employed. A third and still smaller 

 scale of 1:250,000, or about four miles to one 

 inch, has been used in the desert regions of the 

 far West. ' A few special maps on larger scales 



The sheets on the largest scale cover 15' of lati- 

 tude by 15' of longitude; those on the intermedi- 

 ate scale, 30' of latitude by 30' of longitude; and 

 those on the smallest scale, 1° of latittide by 1° 

 of longitude. 



The features shown on this map may, for con- 

 venience, be classed in three groups: (l) water, 

 including seas, lakes, ponds, rivers and other 

 streams, canals, swamps, etc.; (2) relief, including 

 mountains, hills, valleys, cliffs, etc.; (3) cuUtt/re, 

 i. e., the works of man, such as towns, cities, 

 roads, railroads, boundaries, etc. The conven- 

 tional signs used for most of these features are 

 shown and explained in the marginal columns 

 herewith. 



All water features are shown in hkie, the 

 smaller streams and canals in full blue lines, and 

 the larger streams, lakes, and the sea by blue 

 water-lining. Certain streams, however, which 

 flow during only a part of the year, their beds 

 being dry at other times, are shown, not by full 

 lines, but by lines of dots. Ponds which are dry 

 during a part of the year are shown by oblique 

 parallel lines. Salt-water marshes are shown by 

 horizontal ruling interspersed with tufts of blue, 

 and fresh-water marshes and swamps by blue 

 tufts with broken horizontal lines. 



The land features of the relief, usually repre- 

 sented on maps by shading of some sort, with 

 pen or brush, are here shown by contour lines in 

 brown. Each contour passes through those points 

 which have the same altitude. If one follows a 

 contour on the ground one will go neither uphill 

 nor downhill, but on a level. 



By the use of contours not only are the shapes 



of the pj 

 the elevi 

 contour 

 mean se 



above s. 



mrrr cue s, 



ains, hills, and mountains shown, but also 

 itions. The line of the sea-coast itself is a 

 line, the datum or zero of elevation being 

 a-level. The contour line at, say, 20 feet 

 !a-level is the line that would be the sea- 

 sea were to rise or the land to* sink 

 20 feet.^ Such a line runs back up the valleys 

 and for-^ ^ard around the points of hills and spurs. 

 On a ge ^^^^ slope this contour line is far from the 

 present coast line, while on a steep slope it is 

 near it. Thus a succession of these contour lines 

 far apai' ^ Qiap indicates a gentle slope ; if 



close td getter, a steep slope; and if they run 

 togethej' ill one line, as if each contour were 

 vertical! J under the one above it, they indicate a 

 cliff. 1(1 many parts of the country are depres- 

 sions oriii<^llows with no outlets. The contours of 

 course s|'ii'i'<^und these, just as they surround hills. 

 Those small hollows known as sinks are usually 

 indicated ^7 hachures, or short dashes, on the 

 inside \^ curve. Certain contours, usually 

 every tp^li one, are accompanied by numbers 

 stating [elevation above sea-level. Many other 

 heights,vi°strumentally determined, are also given, 

 the nunPer in each case being placed in close 

 proximijty to the point to which it applies. 



The ^/orks of man are shown in blach, in which 

 color al^ lettering also is printed. Boundaries, 

 such as 3tate, county, city, land-grant, reservation, 

 etc., are shown by broken lines of different kinds 

 IScl Av^nts. Cities are indicated by biack~~ 

 blocks, representing the built-up portions, and 

 country houses by small black squares. Roads 

 are shown by fine double lines (full for the 

 better roads, dotted for the inferior ones), trails 

 by single dotted lines, and railroads by full black 

 lines with cross lines. Other cultural features 

 are represented by conventions easily understood. 



The sheets composing the topographic atlas are 

 designated by the name of a principal town or of 

 some prominent natural feature within the dis- 

 trict, and the names of adjoining published sheets 

 are printed on the margins. The sheets are sold 

 at five cents each when fewer than 100 copies are 

 purchased, but when they are ordered in lots of 

 100 or more copies, whether of the same sheet or 

 of differijnt sheets, the price is two cents each. 



The topographic map is the base on which the 

 facts of geology and the mineral resources of a 

 quadrangle are represented. The topographic 

 and geologic maps of any quadrangle are finally 

 bound together, accompanied by a description of 

 the district, to form a folio of the Geologic Atlas 

 of the United States. The folios are sold at 

 twenty-fi;Ve cents each, except such as are unusu- 

 ally comjjrehensive, which are priced accordingly. 



Applications for the separate topographic 

 maps or for folios of the Geologic Atlas, accom- 

 panied by the cash or by post-office money order 

 (not postage stamps), should be addressed to- — 



TliE DIRECTOR, 



United States Geological Survey, 



Washington, D. O. 



October, 1897. 



0^ 



