VIII 



ADVERTISEMENT. 



21. Wells of Northern Indiana, by Frank Leverett. 1899. 8°. 82 pp. 2 pi. 



22. Sewage Irrigation, Part II, hy George "W. Rafter. 1899. 8°. 100 pp. 7 pi. 



23. Water-Right Problems of Bighorn Mountains, by Elwood Mead. 1899. 8°. 62 pp. 7 pi. 

 2-t. Water Resources of the State of New York, Part I, by George W. Rafter. 1899. 8°. 



99 pp. 13 pi. 



25. Water Resources of the State of New York, Part II, by George W. Rafter. 1899. 8°. 

 101-200 pp. 12 pi. 



26. Wells of Southern Indiana (Continuation of No. 21), by Frank Leverett. 1899. 8°. 64 pp. 



In press: 



27. Operations at River Stations, 1898, Part I. 1899. 8°. 100 pp. 



28. Operations at River Stations, 1898, Part II. 1899. 8°. 101-200 pp. 



In preparation: 



29. Wells and Windmills in Nebraska, by Edwin H. Barbour. 



30. Water Resources of the Lower Peninsula of Michigan, by Alfred C. Lane. 



TOPOGRAPHIC MAP OF THE UNITED STATES. 



When, in 1882, the Geological Survey was directed by law to make a geologic map of the United 

 States there was in existence no suitable topographic map to serve as a base for the geologic map. 

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

 area of the country, excluding Alaska, has 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 

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

 About 900 sheets have been engraved and printed; they are tabulated by States in the Survey's 

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



The map sheets represent a great variety of topographic features, and with the aid 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 in high schools, academies, and 

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



1. Physiographic types, by Henry Gannett, 1898, folio, consisting of the following sheets and 4 

 pages of descriptive text: Farg'o (N. Dak.-Minn.), a region in youth; Charleston (W.Va.),a region in 

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

 (Cal.), a young volcanic mountain; Eagle (Wis.), moraines; Sun Prairie (Wis.), drumlins; Donald- 

 sonville (La.), river flood plains; Boothbay (Me.), a fiord coast; Atlantic City (N. J.), a barrier-beach 



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 iu 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 bound 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 remaiuder 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. 



