746 THE ILLINOIS GLACIAL LOBE. 



who has examined the county in some detail, that the greater part of it has 

 never been glaciated. 1 



The upland portion of this county is sparsely settled, and in conse- 

 quence few wells have been made. Cistern water furnishes those who have 

 not the money to sink deep wells. In the Illinois and Mississippi bottoms 

 there are rich farms, and the wells obtain water at depths of 30 to 60 feet 

 in the sand of the river bottoms. 



JERSEY COUNTY. 

 GENERAL STATEMENT. 



Jersey County is situated on the east side of the Illinois River, extend- 

 ing to the mouth of that stream and a few miles down the Mississippi. It 

 has an area of 360 square miles, with Jerseyville as the county seat. The 

 northern part of the county is tributary to Macoupin Creek. The central 

 portion drains westward through Otter Creek to the Illinois River. The 

 southeastern portion drains southward through Piasa Creek to the Missis- 

 sippi River. These streams afford good drainage. There is also a coating 

 of loess which absorbs the rainfall rapidly. 



Along the southern border of the county an elevated ridge formed 

 by an upheaval of the rock strata rises in places to an altitude of 400 

 feet above the Illinois and Mississippi rivers, that flow along its base, and 

 nearly 200 feet above the portion of the county to the north. Aside from 

 this ridge the features of Jersey County are quite similar to those of 

 Greene County. The northern portion slopes to the trough-like depres- 

 sion occupied by Macoupin Creek. A low ridge having rock at slight 

 depth leads westward past Jerseyville, separating the drainage basin of 

 Macoupin Creek from the basins of Otter and Piasa creeks. A few drift 

 knolls and ridges occur in the western and southern parts of the county, 

 the highest of which rise perhaps 75 feet above bordering plains, and 

 which are a continuation of the belt in western Greene County, noted 

 above. The belt of knolls is traceable nearly to the Mississippi bluffs 

 south of Newbern, in the southern part of the county. 



The drift, as in counties to the north and east, consists mainly of till. 

 Its thickness ranges from 20 feet or less up to fully 100 feet. Records of 

 eight borings which reach rock show an average of 30 feet, but preglacial 



1 Proc. Am. Assoc. Adv. Sci., Washington meeting, 1891, pp. 251-253. 



