750 THE ILLINOIS GLACIAL LOBE. 



In the vicinity of Troy wells are obtained at about 30 feet. The 

 loess at this village is 12 or 15 feet in depth. 



In the vicinity of St. Jacobs wells occasionally enter rock at depths of 

 4o or 50 feet if on low ground between the drift ridges. The drift is prob- 

 ably much thicker on the drift ridges, though no records of deep wells were 

 obtained. 



At Highland the wells on low g-round among the drift ridges enter 

 rock at 25 to 50 feet, but many are obtained without reaching the rock. 

 North and east of Highland wells usually obtain water at about 20 feet 

 without entering rock. 



At Grant Fork rock occurs at a level only 20 feet below the upland 

 plain, and several wells west of this village have been drilled into the rock 

 a few feet. No data were obtained concerning the depth of wells in the 

 northeast fourth of the county. 



BOND COUNTY. 

 GENERAL STATEMENT. 



Bond County is situated east of Madison, in the south-central part of 

 the State, and has an area of 380 square miles, with Greenville as its county 

 seat, The greater part of the county is drained southward through Shoal 

 Creek, a tributary to Kaskaskia River. The Kaskaskia touches the south- 

 east corner of the county. The streams afford rather imperfect drainage, 

 and the white clay which covers the glacial drift is a slow absorbent of rain- 

 fall. The excess of rainfall is therefore largely disposed of by evaporation 

 except on the immediate border of drainage lines. 



A system of drift ridges leads across the county from northeast to 

 southwest. There are also scattering knolls over all of the county. 

 These knolls and ridges rise in some cases 50 or even 75 feet above the 

 bordering plains 



The thickness of the drift is known at but few points. Six borings 

 which have reached rock show an average thickness of 85 feet, which is 

 probablv not far from the average for the county. The upper 20 feet con- 

 sist of yellow or ash-colored clays, which in places assume a sandy structure 

 and supply water for the majority of wells. The deeper portion of the 

 drift consists usually of blue till, but a boring at Greenville shows a large 

 amount of sand and gravel. 



