682 THE ILLINOIS GLACIAL LOBE. 



feet, or even more, many of them entering limestone before obtaining a 

 strong vein of water. 



A portion of the Illinois-Mississippi divide is flat and poorly drained, 

 but the portions of the county adjacent to the Mississippi, and also to Bear 

 Creek and to Crooked Creek, are greatly eroded. 



INDIVIDUAL WELLS. 



At Dallas, on the northern border of the county, in the Mississippi 

 Valley, wells are usually obtained at 20 to 35 feet, mainly in limestone. 

 Occasionally they are sunk to a depth of 150 feet. 



At Nauvoo, on the brow of the Mississippi bluff, in the northwest part 

 of the county, the wells are usually obtained at about 20 feet, in -sand. 

 Rock is entered at 25 to 30 feet, but wells seldom reach it. 



At Laharpe, on the upland plain, in the northeast part of the county, 

 the strong wells are obtained in sand below till at a depth of about 60 feet. 

 One well made by Mr. Bainter enters rock at 100 feet. 



In the vicinity of Webster and Fountain Green, in the east part of the 

 county, wells 50 feet in depth do not reach rock. They are mainly through 

 till. Between these villages and Laharpe there is an area of several 

 square miles in which the rock is so near the surface that sink holes abound. 



At Carthage the public water supply is obtained from two deep wells, 

 one of which terminated in the St. Peter sandstone at 1,000 feet, but the 

 other continued to a depth of 1,700 feet. Water veins are struck in the 

 Niagara limestone at about 750 feet; in the Galena limestone at 865 feet, 

 and in the St. Peter sandstone at 975 feet, The head is about 16 feet below 

 the surface, or 660 feet above tide. The water is rather unpleasant on 

 account of salinity. The following record of strata penetrated by one well 

 before reaching the St. Peter is taken from the Geology of Illinois: 1 



Section of deep well at Carthage, Illinois. 



Feet. 



Drift, clay, sand, ami gravel 214 



White limestone 70 



Shale 355 



Limestone 336 



St. Peter sandstone, penetrated i 25 



Total depth 1, 000 



At Elvaston wells are obtained at 12 to 16 feet, and also at 20 to 30 

 feet, from beds of gravel associated with till. 



1 Vol. VIII, p. 65. 



