liv FISHES OF ILLINOIS 



boro, and West Shoal creek is deflected eastward 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 

 flrst 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 the ridges, and it has but few prom- 

 inent ridges and knolls on its east below that point. At its mouth 

 the stream has an elevation 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 immediate blufi^s stand at the general 

 level of the bordering uplands. 



Big Muddy River System 



Big Muddy River system drains an area of 2,374 square miles 

 lying in an elliptical shape, with a major axis about 70 miles long 

 running almost north and south, and a minor axis about 50 miles 

 long. This drainage basin includes the greater part of Williamson, 

 Franklin, Jefferson, Perry, and Jackson counties, the southeastern 

 portion of Washington county, and the southern part of Marion 

 county, which form the extreme southwestern part of the district 

 covered by the Illinoisan drift sheet, lying in the low section just 

 north of the Ozark ridge. The lower 20 miles of the river flows 



