172 PROCEEDINGS OF THE INDIANA ACADEMY OF SCIENCE. 



inches, and is bounded by parallels and meridians. Each four cornered 

 division of land, corresponding to an atlas sheet, is called a "quadrangle," 

 and the scale used is usually two miles to an inch. On these sheets are 

 shown three groups of features: (1) water, including streams, lakes, ponds, 

 canals, etc. (2) relief, shown by contour lines of mountains, hills, valleys, 

 etc. ; (3) culture or works of man, as towns, cities, roads, railroads, etc. This 

 topographic sheet is the base on which the facts of geology and the mineral 

 resources of the quadrangle are represented. The topographic and geologic 

 maps of a quadrangle are finally bound together and with descriptive text, 

 form a folio of the "Geologic Atlas of the United States." 



In 1902, the first one of these completed folios, treating of a quadrangle 

 wholly within the State of Indiana, was issued.* It treated topographically 

 and geologically a quadrangle of 938 square miles in southwestern Indiana and 

 included nearly the whole of Pike County and considerable portions of Gib- 

 son, Vanderburgh, Warrick, Spencer and Dubois Counties. It was called the 

 Ditney folio, since the quadrangle included the Ditney Hills, which are a 

 prominent t()pograi)hic feature in the southwestern i)art of the area covered. 

 The general and j^jleistocene geology of tlie Ditney folio were worked out and 

 mapped by Myron L. l''uller, and the economic geology by George H. Ashley. 

 Both are given in great detail and the folio furnishes a i)ermanent and most 

 valuable reference work on the area covered. 



Another notable work on glacial geology was issued by Krank Leverett 

 in 1902.1 It is a quarto volume of 802 pages and 2(5 maps and plates and 

 is entitled "Glacial Formations and Drainage Features of the Erie and 

 Ohio Basins." He includes much information of interest and value on the 

 lUinoian drift of southeastern Indiana, on the earl.y Wisconsin drift of the 

 same region, on the drainage systems of the State and on the great Glacial 

 Lake Maumee. a portion of which once extended into northeastern Indiana 

 and drained into the Wabash River. (Me valuable feature of the volume is 

 a Bibliography of Glacial Geology of the U. S. brouglit dowii to the year 

 1900. 



A second folio of the U. S. atlas was issued in 1904 which covered a quad- 

 rangle of 938 square miles in southwestern Indiana and southeastern Illinois, 

 and included the greater parts of Vanderburg, Posey and (iibson Counties in 

 the former state. It is called the Putoka folio, after the town and river of that 

 name in (Jibson (\)unty. The area covered adjoins that of the Ditney folio 

 on the west and takes in the cypress swamp area of southwestern Knox 

 County. The geologic work was done by M. L. Fuller and F. G. Clapp. 

 Very full notes on the glacial economic geology of this region are given, 

 and it also includes a list, with measurements, of the larger trees and shrubs 



*In the making of these quadrangle maps and folio.s the V. S. Survey properly 

 ignores all state and county boundaries. A folio put out in 1900, and known as the 

 Danville folio, includcfl a narrow strij) along the western side of Warren and Ver- 

 million Counties, Indiana, and a seeond, known as the Chicago folio, issued in 1902, 

 comprised a part of the; northwestern corner of Lake County. 



JMonograjih XLI, U. S. Geol. Survey. 



