186 GLACIAL FORMATIONS OF ERIE AND OHIO BASINS. 



fall of the streams being adequate to g-ive rapid escape for the surplus rainfall. 

 The streams make a descent of 300 to 500 feet, in some cases, within a dis- 

 tance of 10 to 20 miles. Notwithstanding this descent tliere are very few 

 waterfalls. The only notable ones occur in southeastern Indiana, where 

 the drift deposits have obstructed the old valleys and led to the deA^elopment 

 of new lines of drainage. In the unglaciated portion of southern Indiana 

 there are but few rock rapids, and, so far as the writer is aware, no waterfalls. 

 The gradients of streams, though steep, show a gradual lessening in rate of 

 descent in passing from source to mouth and a general disregard for hardness 

 of strata, such as results only from maturing of a drainage system. The 

 rapid rate of descent is not favorable to the development of broad flood 

 plains, yet there is usually a flood plain having several times the breadth of 

 the stream bed. In this respect the tributaries, as noted above, have accom- 

 plished more work in proportion to their size than the Ohio. It is difiicult 

 to realize that the broad valleys of small streams in southwestern Indiana 

 were begun at no earlier date than the narrow valleys of the higher district, 

 yet such was probably the case. 



WABASH RIVER SYSTEM. 



The drainage basin of the Wabash embraces an area of about 33,000 

 square miles, distributed as follows: In Ohio, 400 square miles; in Indiana, 

 24,350 square miles; in Illinois, 8,250 square miles. It drains, therefore, 

 slightly more than two-thirds of Indiana, the area of the State being 35,910 

 square miles. Of the portion in Indiana, about one-half is embraced in the 

 drainage area of the East White and West White rivers. By including 

 these drainage areas with the Wabash the entire watershed has a nearly 

 symmetrical, broadly ovate form. Not including the White River system, 

 the Wabash watershed is an unsymmetrical, elongated tract, curving around 

 White River. 



Only a small part of the Wabash watershed lies outside the glacial 

 boundary. The Wabash and West White rivers lie within that boundary 

 for their entire length. The East White flows within the glacial boundary 

 to western Jackson County, but from that point to western Martin County 

 it is outside the drift. It enters the drift-covered district in its lower course 

 near the corners of Martin, Davis, and Dubois counties, and remains within 

 the glacial boundary from that point to its mouth. The greater part of 



