784 THE ILLINOIS GLACIAL LOBE. 



Ridgway are in several instances sunk to a depth of over 50 feet, mainly 

 through sand. Wells west and northwest from this village are usually 

 sunk through till, and one well 3 miles west is reported to have reached a 

 depth of 75 feet without entering rock, mainly through till. A blue till 

 was entered at about 25 feet. 



Near Cottonwood rock is entered at only 20 feet and the drift is 

 largely sand. Rock is found at slight depth between Cottonwood and 

 New Haven. 



At Shawneetown wells usually obtain water at 25 to 40 feet in a 

 sandy gravel An oil boring entered rock at 112 feet. A well at the 

 fair grounds 86 feet in depth did not reach the rock. 



THE UNGLACIATED COUNTIES OF SOUTHERN ILLINOIS. 

 GENERAL STATEMENT. 



There are seven counties in the southern end of the State — Hardin, 

 Polk, Johnson, Union, Alexander, Pulaski, and Massac — which are situated 

 outside the limits of the glacial boundary. The four first named are trav- 

 ersed by an elevated ridge, known as the "Ozark uplift," which passes 

 nearly east to west from the Ohio River just below Shawneetown to the 

 Mississippi River at Grand Tower. The crest of this ridge is generally 

 about 400 feet above the Ohio and Mississippi rivers, but occasional knobs 

 along it reach an elevation of 500 and even 600 feet above the river. The 

 most rugged portion of the ridge is found in the northern 6 or 8 miles of 

 these counties and extends slightly into the counties on the north — Jackson, 

 Williamson, Saline, and Oallatin, as noted above. 



South from this elevated and rugged portion of the ridge there is a 

 somewhat hilly tract with lower altitude, which extends to the lowlands 

 covered by Tertiary gravel, which occupy much of the three southern coun- 

 ties of the State — Alexander, Pulaski, and Massac. 



Although not covered by the ice sheet, this district has received deposits 

 of glacial age which affect to some extent the condition of drainage and the 

 character of the soil. 



The Ohio and Mississippi valleys have been filled with deposits of sand 

 and fine gravel to a depth probably not less than 100 feet. There are also 

 alluvial deposits outside the line of the present Ohio which were probably 

 made at the time of the filling of the main valleys. A broad valley, known 



