736 THE ILLIXOIS GLACIAL LOBE. 



At Lerna, which is situated on the crest of the outer moraine of the 

 Wisconsin drift, wells have occasionally reached a depth of 100 feet with- 

 out entering' rock. One made by Mr. Todd, one-half mile northwest of the 

 village, and another by Mr. Fan-is in section 11, each have a depth of 100 

 feet and are mainly through blue till. 



A well near Farming-ton, made by Mr. T. Allison, reached a depth of 

 132 feet without entering rock, mainly through blue till. East from this 

 well, in the Embarras Valley, rock is exposed up to a level within 75 feet 

 of that of the well mouth. 



At Diona, on the plain outside the Wisconsin drift sheet, wells are 

 obtained at a depth of only 12 feet, and are mainly through gravel. 



CUMBERLAND COUNTY. 

 GENERAL STATEMENT. 



Cumberland County is situated south of Coles, in the east-central part 

 of the State, with Toledo as the county seat, and it has an area of 350 

 square miles. The Embarras River leads southward through the east- 

 central part of the county and drains its eastern half. The western part is 

 tributary 'to the Little Wabash River, which leads southward near the county 

 line. This county is strikingly in contrast with Coles County on account of 

 the absence of the Wisconsin drift sheet, which covers only a few square 

 miles on its north border. Its surface is covered with the deposit of white 

 clav which is so prevalent in southern Illinois outside the limits of the Wis- 

 consin drift. This clay absorbs water so slowly on the interfluvial tracts of 

 Cumberland County that most of the water not removed by the streams is 

 evaporated. The surface is very level, and this feature works to the disad- 

 vantage of the development of drainage systems. There is, however, a 

 much more mature system of drainage here than on the Wisconsin drift 

 sheet in Coles County, a feature which points strongly to the comparative 

 freshness of the latter sheet and recency of its deposition. 



The thickness of the drift is known at but a few points, and these are 

 in the vicinity of the Embarras River. In places the rock occurs along 

 this river at a level only 30 or 40 feet below the level of the uplands, but 

 in other places wells near the river show that the drift extends fully 50 feet 

 below the bed of the stream, or over 100 feet below the level of the uplands. 

 Beneath the white clay, which is usually but 4 or 5 feet in thickness, there is 



