SALINE RIVER DRAINAGE BASIN. 527 



the valley becomes constricted to a width of about a mile in its passage 

 through the elevated ridge which there borders the Mississippi Valley. 

 Little Muddy River and Beaucoup Creek, with their principal tributaries 

 also flow through broad preglacial channels which carry heavy deposits of 

 drift and alluvium. 



Possibly the watershed of Crab Orchard Creek has received important 

 modifications as a result of glaciation. The headwater portion of the 

 South Fork of Saline River, a tributary of the Ohio, leads down directly 

 toward Crab Orchard Creek from the elevated portion of the " Ozark 

 Ridge " to a low plain filled to a considerable depth with glacial deposits. 

 It there turns abruptly eastward, following nearly the glacial boundary. 

 It probably continued northwestward into Crab Orchard Creek in preglacial 

 times. A considerable area in northwestern Williamson County also has 

 been filled to such a depth with glacial drift that the preglacial lines are 

 completely concealed. Throughout the greater part of the Big Muddy 

 watershed the drift is very thin, and rock divides separating the preglacial 

 drainage areas are plainly discernible. 



SALINE RIVER DRAINAGE BASIN. 



This small watershed tributary to the Ohio drains the portion of south- 

 eastern Illinois immediately north of the " Ozark Ridge." The South Fork 

 follows closely the base of the ridge, receiving small tributaries which 

 descend the slope of the ridge. The lower course of the main stream is 

 also along the base of the ridge. The Middle Fork rises in southeastern 

 Franklin County and takes a southeastward course past Harrisburg into the 

 South Fork, draining much of Saline County. The North Fork has its 

 source in western Hamilton County and leads southeastward, draining the 

 south half of Hamilton, the northeast part of Saline, the southwest part of 

 White, and the west part of Gallatin County, joining the South Fork at 

 the town of Equality, about 12 miles west of Shawneetown. 



These three forks of the Saline River, and also their principal tribu- 

 taries, are, in the main, reestablished along preglacial lines and take mean- 

 dering courses through broad valleys which have been filled to an elevation 

 of 50 to 100 feet or more above their rock bottoms. As above noted, a 

 small part of the watershed of South Fork has probably been added to 

 this drainage system as a result of glaciation, but with this exception no 



