514 THE ILLINOIS GLACIAL LOBE. 



and also the general features of its several tributaries in the headwater por- 

 tion, may be seen by reference to the Dunlap topographic sheet. 1 



FARM CREEK. 



This small eastern tributary of the Illinois which enters directly oppo- 

 site the city of Peoria has its source in the Bloomington morainic system. 

 As previously noted, it carries a moraine-headed terrace which opens into 

 the Illinois Valley at a level about 170 feet above the stream, thus showing 

 that at the Bloomington substage of glaciation the valley was filled to this 

 unusually high level in that vicinity. The stream has now opened a valley 

 down to the level of the 50-foot terrace which borders the Illinois, that 

 offers a convenient line for approach to Peoria from the east, which is 

 utilized by several railway lines. 



MACKINAW RIVER. 



This important tributary of the Illinois has a drainage area of about 

 1,200 square miles, which may conveniently be divided into three sections: 

 (1) The headwater portion, lying inside the main ridges of the Bloomington 

 morainic system; (2) the middle portion, comprising the section crossing 

 the Bloomington and Shelbyville morainic systems and the narrow plain 

 separating them; (3) the lower portion, embracing the meanders of the 

 river through the Illinois River bottoms. 



The upper portion drains a somewhat elevated till plain in north-central 

 McLean and eastern Woodford counties, lying between the inner large 

 moraine and Cropsey Ridge, a minor moraine of the Bloomington system. 

 The length of this portion of the river is about 40 miles, and in much of its 

 course it flows near the south border of the minor moraine. Several tribu- 

 taries heading in the large moraine lead northward to the river across a 

 sloping plain. Another tributary — Panther Creek — which drains several 

 townships in eastern Woodford County, leads southwestward to join the 

 river at the point where it enters the middle course. The streams in this 

 upper portion have generally very shallow channels, seldom more than 25 



1 1 am informed that by mistake an uncorrected photograph copy of the Dunlap sheet was sent 

 to the engraver, instead of a corrected copy. The error involves chiefly an omission of a 50-foot 

 contour on the uplands west of the Illinois. This should be borne in mind in the examination of the 

 Dunlap sheet. 



