WELLS OF WILL COUNTY, ILLINOIS. 649 



the Kankakee, which joins the Des Plaines, just west of the county line, 

 to form the Illinois River. 



The northwest part of the county and adjacent portions of Dupage 

 and Cook counties are occupied by the Valparaiso morainic system from 

 which drainage lines lead to the southwest across a much lower region, the 

 altitude of the crest being about 750 to 800 feet, while the plain south- 

 west of it stands but 600 feet in average elevation, and scarcely reaches 

 675 feet where highest. The extreme western border of the county is 

 occupied by the Minooka till ridge from the north line southward to the 

 head of the Illinois River. 



Rock is extensively exposed in the southwestern and western parts of 

 the county, but is seldom encountered even in wells in the eastern part. 

 The average distance to rock in 55 wells situated in the low district outside 

 the Valparaiso moraine is 43 feet, which probably represents the approxi- 

 mate average for that portion of the county. Forty -two other wells, situ- 

 ated mainly along the Valparaiso moraine, though having an average depth 

 of 76 feet, do not enter rock. The thickness in that portion of the county 

 probably exceeds 100 feet, though in places rock is near the surface. Along 

 the valleys there are extensive gravel or sand deposits and the southwestern 

 portion of the county is covered with sand dunes. The Valparaiso moraine 

 and the plain southwest of it have at surface till to a depth of 25 to 50 feet 

 or more, beneath which sand and gravel is often found. The presence of 

 this sand and gravel beneath the till renders this county one especially well 

 favored for an adequate supply of excellent water at shallow depths. Very 

 few wells, aside from deep artesian wells, have been sunk to a depth of 

 100 feet. 



INDIVIDUAL WELLS. 



The city of Joliet obtains its public water supply from three wells 

 1,200 feet and one 1,700 feet in depth. The shallower ones terminate in 

 the St. Peter sandstone and the deeper one probably in the Lower Magnesian, 

 though it may reach Potsdam strata. The head is about 40 feet above the 

 surface, or 575 feet above tide. Each well has a capacity of about 500 

 gallons per minute. The water is moderate^ hard, but of pleasant taste. 

 The deepest well is cased only 325 feet and its water has a temperature 

 of 45° F. Mr. F. W. Dewey, superintendent of waterworks, reports that 

 the water can be lowered by pumping to a depth of 70 feet below the 



