THE TOPOGRAPHIC ATLAS OF THE UNITED STATES 



" In 1882 the United States Geological Survey began the con- 

 struction of a topographic map of the country. The work has 

 now been in progress fourteen years, and about 600,000 square 

 miles have been mapped. The areas shown on these maps are 

 scattered widely over the country and represent a great variety 

 of topographic features, and the map sheets, with the aid of de- 

 scriptive text, can be used to illustrate topographic forms. This 

 led the Director to propose the publication of an educational 

 series of folios, for use wherever geography is taught in high 

 schools, academies, and colleges. Authority for their publica- 

 tion and sale was granted by Congress in an act approved March 

 2, 1895. . . . The first folio of the series presents on ten 

 maps illustrations of some of the simplest and most character- 

 istic types of topography to be found in those parts of the United 

 States which have thus far been mapped. Succeeding folios 

 will illustrate more complex forms." 



So Henry Gannett, Geographer of the United States Geolog- 

 ical Survey, introduces an illustrated treatise in folio form on 

 the " Land Forms of the United States." * 



When geographic exploration brought to the knowledge of 

 men the unparalleled Grand Canyon of the Colorado and the 

 picturesque plateau country adjacent, the way was prepared for 

 the discovery of new principles in geographic development; in 

 good time Powell descended the Canyon, and he and his collab- 

 orators surveyed the plateau country, and as the work pro- 

 gressed the " baselevel of erosion " was recognized. The idea 

 quickly took root, and grew into one of the fundamental princi- 

 ples of earth-science ; spreading eastward into provinces already 

 reconnoitered or surveyed, it was found to afford a new means 

 for interpreting earth-history, and thereafter the later stages in 

 the geographic development of the continent were read from land 

 forms as well as from fossil plants and animals. The principle 



* Department of the Interior | United States Geological Survey | Charles D. Walcott, 



Director | | Topographic Atlas | of the | United States | Physiographic Types | by | 



Henry Gannett | | [List of Contents, etc.] | Folio 1 Physiography | Washington, 



D. C | Engraved and printed by the U. S. Geological Survey | S. J. Kiibel, Chief En- 

 graver | 18'J8. 



343 



