GEOLOGICAL AND NATURAL HISTORY SURVEY. 41 



waters, excepting the valley of Hickory Creek, which enters the 

 Des Plaines at Joliet. This valley has a moraine-headed terrace, 

 setting in at the outer border of the moraine in Sec. 17, New 

 Lenox Township. It has a gently undulating surface for a mile or 

 more out from the border of the moraine; its surface then becomes 

 plain. This gravel plain is nearly as high as the bordering till 

 plains 620 to 630 feet A. T. and 60 to 70 feet above the present 

 stream. 



On the east side of the West Du Page River, from Naperville 

 northward, the gravelly deposits of the moraine graduate into 

 terraces or gravelly aprons, which lead down the valley. The low 

 gravelly knolls of the moraine disappear in a nearly plane sur- 

 faced apron on descending to the border of the river. This gravel 

 apron is not so extensive as the deposits of the lower Du Page, 

 above described, and is now seen only as remnants along the valley 

 border. 



The East Du Page throughout its entire length drains a 

 broad slough, which separates morainic ridges. Its bottom is said 

 to be underlain by deposits of gravel and cobble. 



