WELLS OF LOGAN COUNTY, ILLINOIS. 707 



The blue till extends to about 80 feet. At this depth a black mucky soil 

 containing wood is found, which is underlain by a green clay, apparently a 

 swamp subsoil. The muck and associated green clay are often several feet 

 in thickness. They rest upon a harder till than that which overlies them. 

 Occasionally gas is struck in sand near the level of the buried muck, but 

 not in sufficient amount to be utilized for fuel. 



LOGAN COUNTY. 

 GENERAL STATEMENT. 



Logan County is situated in the central part of the State, with Lincoln 

 as the county seat, and has an area of 620 square miles. It is drained by 

 Salt Creek and its tributaries, the principal tributaries being Sugar Creek, 

 Kickapoo Creek, and Lake Fork. With the exception of the northeast 

 corner, it lies outside the limits of the Wisconsin drift and its drainage sys- 

 tems are much more mature than those on the Wisconsin drift to the east, 

 though the elevation is about 100 feet lower than on neighboring portions 

 of the Wisconsin drift. In addition to a better drainage system, there is a 

 coating of loess, which absorbs the excess of rainfall much more rapidly 

 than the till which forms the surface of much of the Wisconsin drift, and 

 returns the moisture to the crops in seasons of drought to a larger extent 

 than the till sheet. 



The thickness of drift is known only at a few points in the southwest 

 part, where it is 60 to 100 feet. The thickness in the northern and eastern 

 parts of the county apparently averages at least 150 feet, several wells 

 having reached that depth without entering rock. The drift in the south- 

 ern and eastern portions of the county is largely till, but in the northwestern 

 part it apparently consists in the main of sand and gravel, thus resembling 

 the drift of Mason County, which borders it on the west. 



Wells are usually obtained at depths of 20 or 30 feet, which have 

 sufficient strength to supply stock as well as households. In a few cases, 

 however, wells have been sunk to depths of 100 or even 200 feet. 



INDIVIDUAL WELLS. 



The village of Atlanta, which is situated on the outer moraine of the 

 Wisconsin drift, obtains its supply for the waterworks from a Avell 151 feet 

 in depth, a section of which appears on p. 206. In the vicinity of Atlanta 



