738 THE ILLINOIS GLACIAL LOBE. 



square miles, with Shelbyville as the county seat. The Kaskaskia River 

 traverses the county in a north-and-south direction and drains nearly all its 

 surface. A small area in the southeast part is tributary to the Little Wabash, 

 and the northwest corner of the county is tributary to the Sangamon River. 

 The Shelbyville moraine passes across the northeast part of the county 

 making an abrupt turn at the city of Shelbyville from a westward to a 

 northward course. 



The portion of the county outside the Shelbyville moraine is generally 

 plane, but the west part of the county is dotted with knolls of drift, some 

 of which reach a height of over 100 feet and many are at least 50 feet. 



In the portion of the county occupied by the Wisconsin drift there is 

 a sheet of soft blue till 50 to 100 feet or more in depth, covering the 

 harder till, which extends into the outlying districts. Exposures of the 

 hard till beneath the Wisconsin drift are to be seen along the Kaskaskia 

 River in the vicinity of Shelbyville. There are also along the stream near 

 Shelbyville exposures of the white clay which covers the hard till. 



The drift outside the Wisconsin sheet consists usually of till ; but some 

 of the knolls and ridges contain a large amount of gravel or sand. Rock is 

 often entered in. tins district at a depth of 50 feet or less, except on the drift 

 knolls and ridges, where the distance to rock is usually increased by the 

 measure of the height of the knoll or ridge. 



The wells are usually obtained without entering rock. Those on the 

 Wisconsin drift are frequently sunk to depths of 75 or 100 feet, but those 

 on the older sheet outside the limits of the Wisconsin drift seldom exceed 

 30 feet. 



INDIVIDUAL WELLS. 



At Moweaqua, on the plain outside the Wisconsin drift, in the north- 

 west part of. the county a coal shaft penetrates 65 feet of drift. The upper 

 22 feet is a comparatively soft clay, but the remainder is a very hard blue 

 till. A well in process of excavation at the time the writer was there 

 exposed the following section: 



Section of well at Moiceaqua, Illinois. 



Feet. 



Loess or pebbleless yellow silt 8 



Yellow clay with a few fine pebbles 7 



Deeply oxidized till, very pebbly 9 



Hard blue till at bottom. 



