782 THE ILLINOIS GLACIAL LOBE. 



and ridges having rock nuclei, but which rise only 25 to 50 feet above the 

 bordering lowlands. The streams are generally bordered by broad low- 

 lands, portions of which are thinly covered with drift, as are also the low 

 hills and ridges just mentioned. There are probably filled valleys travers- 

 ing these lowlands, in which the thickness of drift is greater than on the 

 remainder of the county. In this county, as in the neighboring counties 

 on the north and west, the drift is covered with a pebbleless silt several feet 

 in depth. On the hills and ridges this is less compact than the white clay 

 in districts to the north, and the lowland tracts also have usually a more 

 porous silt than the typical white clay. 



The glacial drift consists mainly of a brown till, but where it reaches 

 a depth of 30 feet a blue till is ustially found at bottom. The wells are 

 often sunk into the rock a short distance, and few strong wells were found 

 which obtain a supply from the drift. Their depth seldom exceeds 40 feet. 



INDIVIDUAL WELLS. 



At Texas City, in the northeast part of the county, a well sunk by 

 T. W. Overton reached a depth of 302 feet. Water rises within 8 feet of 

 the surface. An inflammable gas was struck at about 240 feet, which is 

 estimated to have a pressure of 75 pounds to the square inch. 



At Eldorado wells enter rock at about 20 feet after penetrating a few 

 feet of surface silt and a slightly pebbly clay. ■ Water is usually obtained 

 within 30 or 40 feet, A well at Louis Pettinger's, 2 miles east of Eldo- 

 rado, on a low drift knoll, reached a depth of 46 feet without entering rock. 

 The lower part was through a blue clay, probably till. A well made by 

 D. Westbrook, on a low drift knoll 2 miles northeast of Eldorado, reached 

 a depth of 40 feet without entering rock, and a similar depth was reached 

 on a knoll 1 mile north of Eldorado in a well made by L. Lyson. These 

 knolls stand only 10 to 20 feet above the bordering plane tracts. 



In the vicinity of Raleigh the shallower wells obtain water in drift, 

 but a few wells have been sunk into rock, which is entered at about 30 

 feet. In the portion of the county west from the meridian of Raleigh 

 there are numerous low hills with rock nuclei, and wells usually enter rock 

 within 10 or 15 feet of the surface. These conditions continue southward 

 past Harrisburg to the elevated ridge on the border of the county. On 

 this ridge the residents depend largely upon cisterns and springs. 



