ADVERTISEMENT. 



IX 



TOPOGRAPHIC MAP OF THE UNITED STATES. 



When, in I>'8l2, the Geologieal Survey was directed by law to make a geologic- in:i|i of the United 

 States there was iu existence no suitable topographic- map to serve as a base lor I he geologic map. 

 The preparation of such a topographic map was therefore immediately begun. About one-tilth of the 

 area of the country, excluding Alaska, Las now been thus mapped. The map is published in atlas 

 sheets, each sheet representing a small quadrangular district, as explained under the next head- 

 ing. The separate sheets are sold at 5 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 different sheets, the 

 priee is 2 cents each. The mapped areas are widely scattered, nearly every Stale being represented. 

 About !K)0 sheets have been engraved and printed; they are tabulated by States iu the Survey's 

 "List of Publications, 1 ' a pamphlet which may be had on application. 



The map sheets represent a grea t variety of topographic features, and with the a id of descriptive 

 text they can be used to illustrate topographic forms. This has led to the projection of an educational 

 series of topographic folios, for use wherever geography is taught 111 high schools, academies, ami 

 colleges. Of this series the first folio has been issued, viz: 



1. Physiographic types, by Henry Gannett, 1SJIS, folio, consisting of the following sheets and 4 

 pages of descriptive text: l-'argo (N. Dak. -Minn.), a region in youth ; Charleston ( YV.Va. ),a region in 

 maturity ; Caldwell (Ivans. I, a region in old age; Palmyra i Va.), a rejuvenated region ; Mount Shasta, 

 (Cal. ), a young volcanic mountain; Eagle ( \Vis ). moraines; Sun I'rairic i \Yis. ), drunilins; Honaldson- 

 ville(La. ), river Hood plains; Boothbay (Me.), a fiord coast; Atlantic' City ( \. ,1. '. a harrier-beach coast. 



2. Physiographic types, by Henry Gannett, lilOO, folio, consisting of the following sheets and 11 

 pages of descriptive text: Norfolk (Va.-X. C.), a coast swamp; Marshall (Mo.), a graded river; 

 Lexington (Nebr.), an overloaded stream; Harrisburg (Pa.), Appalachian ridges; Poteau Mountain 

 (Ark.-Ind. T.). Ozark ridges; Marshall (Ark.), Ozark Plateau; West Denver (Colo.), hogbacks; 

 Mount Taylor (N. Mex.), volcanic peaks, plateaus, and necks; Cueauiouga (Cal.), alluvial coues; 

 Crater Lake special (Oreg. ), a crater. 



GEOLOGIC ATLAS OF THE UNITED STATES. 



The Geologic Atlas of the United States is the final form of publication of the topographic and 

 geologic maps. The atlas is issued in parts, progressively as the surveys are extended, and is designed 

 ultimately to cover the entire country. 



Under the plan adopted the entire area of the country is divided into small rectangular districts 

 (designated quadrangles), bounded by certain meridians and parallels. The unit of survey is also the 

 unit of publication, and the maps and descriptions of each rectangular district are issued as a folio of 

 the Geologic Atlas. 



Each folio contains topographic, geologic-, economic, and structural maps, together with textual 

 descriptions and explanations, and is designated by the name of a principal town or of a prominent 

 natural feature within the district. 



Two forms of issue have been adopted, a "library edition" and a ''field edition." In both the 

 sheets are hound between heavy paper covers, but the library copies are permanently bound, while 

 the sheets and covers of the field copies are only temporarily wired together. 



Under the law a copy of each folio is sent to certain public libraries and educational institu- 

 tions. The remainder are sold at 25 cents each, except such as contain an unusual amount of matter, 

 which are priced accordingly. Prepayment is obligatory. The folios ready for distribution are listed 



below. 



