556 REPORT OF STATE GEOLOGIST. 



ELEVATION. 



"The highest land in the State, in southern Randolph County, is 

 1,285 feet above tide; the lowest, at the southwestern corner, is 313 

 feet. The area above 1,000 feet comprises 2,850 square miles in three 

 tracts: (l)An irregular area around the headwaters of the White Water 

 River in Union, Wayne, Randolph, Delaware, Henry, Rush, De- 

 catur, Franklin and Ripley counties. (2) A narrow crescentric 

 ridge in Brown County. (3) A considerable area in Steuben, Dekalb, 

 Noble and Lagrange counties. Isolated peaks rise in Brown County 

 to 1,172 feet, and in Steuben to 1,200 feet. The area between 500 and 

 1,000 feet in elevation is 28,800 square miles, and that below 500 feet 

 is 4,700 square miles. The average elevation of the State is 700 feet." 



DKAINAGE. 



"'The general slope of Indiana is to the southwest as indicated by 

 the course of the Wabash River and its tributaries, which drain two- 

 thirds of the State. Of the remaining third, one-half is drained di- 

 rectly to the Ohio, and one-half to Lakes Erie and Michigan, and to 

 the Mississippi through the Illinois." 



PHYSIOGRAPHIC FEATURES. 



The greater part of Indiana is a plain of accumulation; the surface 

 of a sheet of glacial drift, which varies in thickness from a few feet to 

 500 or more. The average thickness is more than 100 feet. It con- 

 sists chiefly of a mass of clay containing more or less gravel and bould- 

 ers. This is locally varied by heaps, ridges, sheets and pockets of sand 

 and gravel, and in the southern part of the State is overlain by a pecul- 

 iar fine silt, called loess. 



The driftless area is a plain of degradation, formed by the removal 

 of the original rock surface to an unknown depth, and now represented 

 by the summits of flat and even topped divides, ridges and hills. 



On the plain occur numerous Mils of accumulation forming the great 

 morainic belts, the result of excessive dumping and heaping up of 

 drift along the margins and between the lobes of the melting ice-sheet. 

 The most impressive examples are found in Steuben, Lagrange, Noble 

 and Kosciusko counties, where they attain a height of 200 feet or more, 

 and are as steep and sharp as the materials will lie. The Ohio slope is 

 studded all over with hills of degradation, blocks and fragments of the 

 original plain left by the cutting out of the valleys between them. 

 These are very conspicuous in the counties of Greene, Daviess, Martin, 



