180 



the north has scarcely any significant ridges. When sand ridges occur 

 on the area they are usually not more tliau 30-50 feet higli. In the dune 

 area some of the elevations will exceed 100 feet. The lower moraine of 

 the Wisconsin sheet presents a distinct ridging in places, with a gently 

 undulating surface, but the range in elevation is slight. The area lying 

 between the Wi-sconsin drift boundary and the farthest advance of the 

 early ice sheet is a flat. to ;geiitly rolling surface. 



Exposures, wells and borings show that the preglacial surface of the 

 drift area was much eroded, and drainage lines well advanced. If the 

 surface could be seen it would perhaps have much the same appearance as 

 the surface of the driftless area. 



The unglaciated region is a thoroughly dissected plateau. The eleva- 

 tion ranges from 350 feet at the southwest corner, along the Ohio, fo 1.147 

 feet, at Weedpatch Ilill in Ilmwn County. The hills iuul ridges vary 

 much in general characteristics, according to the geological formations. 

 r.ut the greater part of the area may be classed as very rugged, no level 

 tracts of very large size occur, and much of the surface is too hilly for 

 cultivation. In general the work of the' glacier in Indiana has been to 

 make the surface more level and of much greater value from an agri- 

 cultural standpoint. 



DRAINAGE. 



The drainage has been greatly inthienccd by the glaciers whicli have 

 invaded the State. Many of the preglacial valleys were filled with drift 

 and have been able to cut out only a part of the material, or in many 

 ca.ses have followed new lines entirely. (liacial water streams have done 

 much on the surface, but most of these lines are represented only by the 

 olrl channels, oi by streams which arc insignificant as compared with the 

 flow from the ice front. In the driftless area doe]) valleys, gorges and ra- 

 vines, are characteristic of the drainage, some of the special drainage fea- 

 tures will be considered under the heading of Rivers and Lakes. 



liiicrs. — All the rivers of the State have been more or less influenced 

 by the glacial action. In the glaciated part there is no uniformity in the 

 drainage lines; in the driftless area a section of drainage worked out in 

 detail will present a perfect dendritic system. 



The Ohio River forms the southern boundary of the State, and flows 

 in a winding course for 352 miles. The valley of the Ohio is very nar- 



