X 



lviii FISHES OF ILLINOIS 



the East and West forks near Greenville. Below this point the 

 valley is more shallow, and the stream soon enters the Kaskaskia 

 basin, where its bed is but little lower than the basin plain. 



East. Shoal creek is bordered closely on the east throughout 

 its entire length by a series of drift knolls and ridges (broken 

 Illinoisan moraines) . Shoal creek passes through a break in this 

 system of ridges just below the junction of the East and West 

 forks, beyond which its course is largely independent of drift 

 ridges. Middle Shoal creek winds about among prominent drift 

 knolls near Hillsboro, and West Shoal creek is deflected east- 

 ward by a ridge of drift at its junction with Middle Shoal creek. 

 The courses of these streams seem to be mainly independent of 

 preglacial lines but largely determined by Illinoisan moraines. 

 East Shoal creek touches the line of a deep preglacial valley 

 near Greenville, but above that point it has opened a new course, 

 in places trenching into the rock. Even the lower course seems 

 to be largely independent of any preglacial line of drainage. 



SILVER CREEK 



Silver creek rises in the southeastern corner of Macoupin 

 county, flowing almost due south through eastern Madison and 

 St. Clair counties and emptying into the Kaskaskia opposite 

 New Athens. It has a length of about 60 miles, draining an 

 area of 500 square miles. The basin averages only about 10 

 miles in width. 



At its source the river has an altitude of about 650 feet. In 

 its first 4 miles it falls 50 feet and in the next 16 miles a descent 

 of 100 feet is made. In the lower part the fall is much less, 

 being only 70 feet in the remaining. 43 miles. 



In its southern half the watershed is diversified by drift 

 ridges and knolls which rise in some cases to a height of 75 feet 

 or more above the border districts. These for a few miles in 

 southeastern Madison county constitute the east border of the 

 watershed, but just south of the line of Madison and St. Clair 

 counties the stream passes through the main belt of ridges, and it 

 has but few prominent ridges and knolls on its east below that 

 point. At its mouth the stream has an elvation of only 370 

 feet, and the surrounding country, aside from the knolls, stands 

 scarcely 400 feet above tide. Silver creek seems to be largely 

 dependent in the direction of its course on glacial influences. It 

 cuts into the rock at numerous points along its course, and its 



