A CENTURY OF GEOLOGY IN INDIANA. 171 



There was issued by the Chicago Academy of Science* in 1897, an illus- 

 trated paper by Leverett entitled "The Pleistocene Features and Deposits of 

 the Chicago Area," which includes much valuable information regarding the 

 drift topography of the northern portions of Lake, Porter and LaPorte 

 Counties, Indiana. Full details are given regarding the Valparaiso Moraine, 

 which "consists of a more or less complex belt of the Wisconsin Drift Sheets 

 and receives its name from the city of Valparaiso, Porter County, which is 

 situated on its crest." The old beaches of the southern end of Lake Michigan 

 are also fully described and much information given concerning the present 

 beaches of the lake and the dune area along its border. 



Another paper by Leverett, issued in 1899 as Monograph XXXVIII of 

 the U. S. Geological Survey and entitled "The Illinois Glacial Lobe" is 

 invaluable to all students of the glacial geology of Indiana. It is a quarto 

 volume of 817 pages, with 24 maps and plates, which discusses in detail the 

 drift deposits of the first invasion of a great ice sheet which "extended south 

 and southeast to the unglaciated tracts of southern Illinois and southern 

 Indiana." The border line of the drift is traced in detail over its tortuous 

 course across Indiana and colored maps showing the glacial boundary and 

 present drainage of southwestern and south-central Indiana are included. 



The Valparaiso Moraine system which, as already noted, covers a portion 

 of northwestern Indiana, and the old "Glacial Lake Chicago," a large extinct 

 lake of the same area also receives much attention in this volume. 



In 1902 Geo. H. Ashley, then connected with the U. S. Geological Survey, 

 publishedf a paper on the "Eastern Interior Coal Field," which was ac- 

 companied by two double quarto-page colored maps showing the exact 

 boundaries of that field which comprises the coal areas of Indiana, Illinois and 

 northwestern Kentucky. Of the field he says: "It is estimated to have a 

 total area of 46,000 square miles, of which 6,500 occupymg parts or all of 

 26 counties, lie in Indiana, 3.5,000 in Illinois, and 4,500 in Kentucky." Ac- 

 counts are given of the stratigraphy of the coal-bearing rocks and the general 

 structure of the field, which "is that of an elongated basin whose lowest 

 portion is in southeastern Illinois, toward which the strata dip from every 

 direction. * * * The dip in Indiana averages about 24 feet to the mile 

 running up to 100 feet to the mile in a few places." 



There are also sections devoted to the number and extent of workable 

 beds and the character of the coal in each State. He says that in Indiana 

 "Coal has been found at 20 horizons, as many as 17 beds having been struck 

 in a single drilling within a vertical distance of 800 feet, most of them being 

 thin, but beds sufficiently thick to be workable occur at eight different 

 horizons, though as a rule not over three are workable at any one point." 



The U. S. Geological Survey in 1882 began the making of parts of a topo- 

 graphic map of the entire United States. This map is published in atlas 

 sheets of widely scattered areas. Each sheet is of convenient size, 20 x 163^ 



*Bull. No. II of the Geol. and Nat. Hist. Survey. 

 J22nd Ann. Rep. U. S. Geol. Surv. iy02.linJ- 205-305. 



