THE SHELBYVILLE MORAINIC SYSTEM. 217 



places. Its surface has about the same altitude as the bordering till plain, 

 35 feet above the Sangamon River. 



At Dalton City, located about 12 miles southeast of Decatur, the bot- 

 tom of the Shelbyville drift sheet is found at 65 feet, and wells have been 

 sunk to a depth of 150 feet without reaching rock. The majority of wells 

 are about 70 feet. It is not uncommon to find beds of black muck below 

 the Shelbyville drift in the vicinity of this village. 



At Bethany, 5 miles southeast of Dalton City, the Shelbyville sheet is 

 apparently only 40 feet in depth. At this depth a greenish clay, associated 

 in places with a black mucky soil, is usually entered. This clay is but a 

 few feet in depth, and is probably an Iowan silt. It is underlain by a hard 

 gray till, called hardpan, which seems to be Illinoian. The tubular wells 

 in that vicinity range in depth from 70 to 140 feet without striking rock. 



At Sullivan the drift, as shown by records published in the Geology of ' 

 Illinois, has a depth of about 200 feet. The public water supply is from 

 wells 100 to 125 feet in depth. The mayor reports that the upper 50 feet 

 is a soft blue till, beneath which considerable sand is penetrated. This is 

 underlain by a hard till which is penetrated 40 feet or more before the water- 

 bearing gravel is reached. 



In northern Coles County, between Humboldt and Fair Grange, wells 

 are 60 to 120 feet in depth without reaching rock. In some wells a hard 

 gray till is struck at about 50 or 60 feet. The overlying till is soft and 

 probably is referable to the Shelbyville sheet. At Oakland, in northeast- 

 ern Coles County, rock is entered at about 50 feet. 



At Kansas, in western Edgar County, rock is entered at 80 feet or less. 

 lu a few cases wells have struck a black soil at about 30 feet, which is 

 probably just below the Shelbyville drift sheet. A well midway between 

 Kansas and Isabel entered rock at only 40 feet, but others in that vicinity 

 50 feet or more in depth do not strike rock. In the eastern part of Edgar 

 County, on Clay's Prairie, rock is occasionally struck at only 20 or 25 feet, 

 and is extensively exposed along Bruillett's Creek, in eastern Edgar County, 

 Illinois, and southern Vermilion County, Indiana. The general thickness 

 of the drift in that region can scarcely exceed 40 feet. 



The Indiana district, immediately north from the Shelbyville moraine, 

 has generally a comparatively thin sheet of drift on the uplands, rock often 

 being struck at 50 feet or less, but in the preglacial valleys the drift may 



