lvi FISHES OF ILLINOIS 



miles. It is about 212 miles long, the narrow upper end reaching 

 within 40 miles of the state of Indiana. The upper third of the 

 basin lies in Wisconsin drift, and the other two thirds in the 

 Illinoisan. The basin is composed of level or undulating 

 country having black soil in the northern part and chocolate to 

 light gray soil in the southern, underlaid by yellow to white clay. 

 Heavy timber lands skirt the rivers, between which lie the 

 prairies. In the southern parts great drift mounds, usually 

 topped with timber, rise often from the midst of the prairies. 



KASKASKIA RIVER 



Kaskaskia River rises in Champaign county in the Cham- 

 paign morainic system and flows southwest, emptying into the 

 Mississippi in Randolph county, near Chester, at an altitude of 

 342 feet. Its descent is generally gradual, the most rapid section 

 of its course being its passage through Moultrie county, where it 

 makes a descent of 55 feet in about 18 miles, or 3 feet to the 

 mile. In the headwater portion there is a fall of only 110 feet 

 in the first 50 miles. In places there are pools several miles in 

 length, the most conspicuous of these being in St. Clair county, 

 where in a distance of 20 miles the fall is scarcely 10 feet. 



The upper 80 miles lies in the Wisconsin drift, the stream 

 emerging from the Shelbyville moraine near Shelbyville. In its 

 headwater portion the channel of the stream is narrow and shal- 

 low to the inner border of the Shelbyville moraine. The banks 

 are muddy as far as Sullivan, but sandy below this. The drainage 

 of this section of the basin was originally very imperfect, and its 

 undeveloped streams were often little more than series of swales 

 and sloughs. Ditches and tile drains have greatly changed these 

 conditions, however, and the run-off is now fairly prompt and 

 complete. In crossing the moraine the Kaskaskia valley has an 

 average depth of nearly 75 feet, and four miles northeast of 

 Shelbyville the bluffs attain a height of 130 feet, although the 

 channel is so narrow that it is not much more than a trench. 

 The valley continues narrow for a few miles after entering the 

 Illinoisan drift, but widens below the mouth of Robinson creek. 

 This stream seems to follow the lower course of a drainage line 

 (probably interglacial) , whose former headwater portion has been 

 concealed by the Shelbyville drift sheet. Its valley has a 

 breadth of nearly half a mile, and the Kaskaskia retains this 

 breadth below the mouth of the creek, increasing to three fourths 

 of a mile in southern Shelby county. These bottoms are gen- 



