ILLINOIS RIVER DRAINAGE BASIN. 519 



course of the stream continues westward to its junction with the Sangamon 

 River, 50 miles below. It receives Lake Fork Creek from the south about 

 5 miles above Lincoln; Kickapoo Creek from the north about 4 miles below 

 Lincoln, and Sugar Creek, also from the north, about 12 miles farther down. 

 Its valley is much broader below the mouth of Lake Fork than above, and 

 it seems probable that a larger stream occupied Lake Fork Valley prior to 

 the Wisconsin invasion than occupied Salt Creek "Valley. Indeed, the latter 

 appears to be almost wholly a post- Wisconsin stream as far down as its 

 junction with Lake Fork. 



Kickapoo Creek finds its source between the two ridges of the Bloom- 

 ington system, a few miles east of the city of Bloomington. Like North 

 Salt Creek, it passes southward through the outer morainic ridge and, as 

 previously noted, becomes the avenue of discharge for a gravel train head- 

 ing in that moraine. It passes through the Shelbyville moraine near the 

 village of Waynesville and skirts its outer border for a few miles west, 

 when it turns southwestward into Salt Creek, entering that stream about 10 

 miles from its point of departure from the Shelbyville moraine. 



The several headwater branches of Sugar Creek find their sources in 

 the depression between the two main ridges of the Bloomington system, 

 and pass thence southwestward through the outer moraine, where they 

 become the avenue of discharge for the trains of gravel connected with 

 that moraine. The several branches converge upon approaching the Shel- 

 byville moraine and unite in the midst of the moraine. Upon emergino- 

 from the Shelbyville moraine, Sugar Creek Valley is separated from Kick- 

 apoo by an interval of only 1£ miles, and this is largely occupied by a 

 plain of gravel built up by the joint work of the two streams. Instead of 

 uniting with Kickapoo Creek, however, Sugar Creek turns westward, and 

 joins Salt Creek about 12 miles below the mouth of Kickapoo Creek. 



Sangamon River receives one important tributary from the south, 

 known as South Fork. It drains the greater part of Christian County, and 

 enters the river in Sangamon County, immediately east of the city of 

 Springfield. An eastern branch of South Fork, known as Flat Fork, has 

 evidently been beheaded because of the Wisconsin drift, in a manner simi- 

 lar to that of Lake Fork. The stream has its present head in the outer 

 border of the Shelbyville 7noraine, but finds a broad shallow valley, far 

 out of proportion to its needs, down which it passes to the Sangamon River. 



