536 THE ILLINOIS GLACIAL LOBE. 



the south end of the old Wabash Bayou by the sediments brought down 

 by the creek, for it seems probable that the creek continued south-westward 

 into the Wabash along the south end of the channel opened by that stream 

 for some time after the abandonment of the channel by the river. The 

 abrupt change in the rate of fall would naturally produce an accumulation 

 of silt at the point where it entered the old bayou of the Wabash, and this 

 may have resulted in the deflection of the stream northward through an 

 unfilled portion of the bayou. The watershed of Big Raccoon and Little 

 Raccoon creeks lies mainly within the Wisconsin drift, but in southern 

 Parke County it lies outside that drift. 



SUGAR CREEK. 



Sugar Creek, another eastern tributary of the Wabash, enters the river 

 about 8 miles above the mouth of Big Raccoon Creek. It drains an area 

 of perhaps 900 square miles, embracing southern Clinton, northern Boone, 

 central Montgomery, southeastern Fountain, and northern Parke counties. 

 Its length is about 80 miles by direct course, but the width of the water- 

 shed scarcely reaches 25 miles at any point, and the average width is not 

 more than 12 miles. 



This stream lies wholly within the limits of the Wisconsin drift, and, 

 with the possible exception of a few miles near its mouth, has a course 

 independent of preglacial lines. Its rock gorges, which set in a few miles 

 below Crawfordsville, afford some of the most picturesque scenery in the 

 State. Above Crawfordsville the stream has a shallow channel which 

 touches the rock at only a few points. At the headwaters the drift is 

 shown by deep wells to have a thickness of 250 to 300 feet. At Craw- 

 fordsville a preglacial valley is crossed whose rock floor is more than 100 

 feet below the present stream. 



This stream cuts through a moraine of the Champaign system in 

 southwestern Montgomery County, below which point it crosses a plain 

 lying north of the moraine. The headwater portion above Crawfordsville 

 lies within the limits of the Erie Glacial Lobe. 



VERMILION RIVER. 



This western tributary of the Wabash drains about 1,500 square miles 

 in eastern Illinois. Its lower course for a distance of about 10 miles lies 

 within the State of Indiana, but it there drains only the immediate borders 



