Hi FISHES OF ILLINOIS 



laid by yellow to white clay. Heavy timber lands skirt the rivers, 

 between w^hich 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 Champaign 

 morainic system and flows southwest, emptying into the ]\Iississippi 

 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, w^here it makes a de- 

 scent of 55 feet in about 18 miles, or 3 feet to the mile. In the head- 

 water 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 emerg- 

 ing from the Shelbyville moraine near Shelby\'ille. In its headwater 

 portion the channel of the stream is narrow and shallow 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 por- 

 tion 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 generally 

 14 to 16 feet above the ordinary stage of water, with sometimes a 

 second bottom a few feet higher. During the wet seasons the river 

 often covers the first bottom to a depth of several feet. The hills on 

 each side of the river are from 60 to 70 feet in height. On entering 

 Fayette county, the river opens into a broad preglacial valley whose 

 course farther north is buried under drift. The valley has a width 

 of about 3 miles near Vandalia, but reaches a greater width farther 



