THE TOPOGRAPHY AND HYDROGRAPHY OF ILLINOIS lix 



t < ) 5 feet high, and generally bordered by scattered patches of timber. 

 In the lower parts the streams are skirted with strips of woodland 

 from one to four miles in width, and the banks are steep and high. 

 Bed-rock is not exposed in the upper portions, but at and below 

 Danville the river has cut into the rock of the coal-measures to a 

 considerable depth. 



Generally speaking, the headwaters of all these streams were 

 originally prairie swales, lying in shallow valleys or in broad de- 

 pressions of an otherwise plain surface. Here they were often 

 choked with weeds in summer, and were very muddy in times of 

 flood, but in their lower courses they often cut deeply into the drift, 

 or even into the underlying rock, forming deep and narrow valleys, 

 sometimes with decidedly gorge-like effect. In comparison with 

 most Illinois streams, however, the waters of the Big Vermilion are 

 in general fairly clear, and the bottoms relatively clean, forming a 

 transition from the typical prairie streams to those characteristic 

 of the adjacent Alleghany plateau. 



LITTLE VERMILION RIVER 



The Little Vermilion River rises in the southeastern corner of 

 Champaign county and flows southeast, east, northeast, and south- 

 west, a distance of about 60 miles, emptying into the Wabash River 

 in Vermilion county, Indiana. Of this length 45 miles lie in Illi- 

 nois. It drains a narrow strip covered by the Champaign till-sheet 

 lying between two moraines, the northern of which completely 

 separates the drainage basin of the Little Vermilion from that of the 

 Vermilion proper. The river rises at an altitude of 710 feet, and 

 falls 30 feet in its first 4 miles. In the next 9 miles a descent of only 

 10 feet is made, below which a fall of SO feet occurs in 4 miles. The 

 descent then becomes more gradual and the stream crosses the state- 

 line at an elevation of about 500 feet. In its upper part it is little 

 more than a prairie drain, but it becomes of more importance farther 

 down, where the banks are 75 to 100 feet high and lined with strips 

 of timber 1 to 3 miles in width. 



EMBARRAS RIVER 



Embarras River drains an area of about 2,000 square miles in 

 eastern Illinois. Its source is in the Champaign morainic system, 

 immediately south of the city of Champaign. For about 20 miles it 

 flows between the outer and the main ridges of the Champaign sys- 

 tem, then cuts through the outer ridge in northern Douglas county. 

 Thence it bears southeast, for about 10 miles, to a small till ridge 



