WELLS OF CHAMPAIGN COUNTY, ILLINOIS. • 701 



CHAMPAIGN COUNTY. 

 GENERAL STATEMENT. 



Champaign County is situated west of Vermilion, and lias an area of 

 1,000 square miles, with Urbana as the county seat. The eastern and 

 northeastern portions are tributary to the Vermilion River. The southern 

 portion contains the headwaters of the Embarras and Kaskaskia rivers, and 

 the northwestern portion is crossed by the Sangamon River. Much of the 

 surface is so level that artificial ditching has been necessary to give good 

 drainage. There are, however, two morainic systems crossing the county. 

 The outer belt of the Bloomington system crosses the northeast corner, while 

 the Champaign morainic system traverses the county in a southeast course, 

 a little to the south of the center. The latter system consists of three dis- 

 tinct ridges in the southeast part of the county, which become united into a 

 single ridge near Champaign, and continue united to southeastern McLean 

 County, beyond which the morainic system is not traceable. The belt 

 belonging to the Bloomington system has an average relief of about 50 feet 

 above the plain bordering it on the .southwest. The Champaign morainic 

 system has even less average relief above the bordering plains. 



In the portion of the county southeast from Urbana the drift has an 

 average thickness of scarcely 100 feet, but throughout the remainder of the 

 county its thickness is much greater. Records of 22 borings which did not 

 reach rock show an average of 171 feet, and it is probable that the average 

 for the county is not less than 200 feet. The drift to a depth of about 100 

 feet is, in the main, a soft blue till of Wisconsin age. On the moraines the 

 depth is correspondingly greater. Prof. C. W. Rolfe, of the University of 

 Illinois, reports that throughout much of the county wells are found to 

 pass through a buried soil immediately below the blue till, and then to 

 enter a harder till. The writer found exposures, of which description has 

 already been given (p. 216), of a peaty muck or soil along the bluffs of 

 the Sangamon River in the western part of the county. 



Many wells have been sunk through the blue till into beds of sand or 

 gravel associated with the underlying harder till, as shown in the discussion 

 below. Throughout much of the county the wells have strong hydrostatic 

 pressure, though they seldom overflow. 



