26 CHICAGO ACADEMY OF SCIENCES. 



THE VALPARAISO MORAINE IN ILLINOIS. 



THE MORAINE, 



Distribution. — At the Illinois and Wisconsin line and for 

 some thirty miles southward the Valparaiso moraine is so closely 

 associated in its outer or west border with earlier moraines that 

 that border is not clearly outlined. Just south of Elgin the mo- 

 raine first becomes distinct, its course there becoming east of 

 south, while the earlier moraines bear west of south. It covers the 

 lake region of western Lake and eastern McHenry Counties, 

 its eastern border in Lake County being nearly coincident with 

 that of the system of small lakes, and slightly east of the water 

 parting between the Fox and Des Plaines Rivers. 



In Cook and Du Page Counties the moraine has a breadth of 

 not less tlian ten miles and in places reaches fifteen miles, its inner 

 border being somewhat irregular. In northern DuPage County 

 it lies entirely within the limits of the county, but farther south it 

 encroaches on western Cook County, the inner border at the 

 Des Plaines River being about four miles east of the county line. 

 The outer border from Wayne to Turner Junction lies just east 

 of the Chicago and Northwestern railroad. South from Turner 

 Junction the West Du Page River follows the border. In south- 

 ern Du Page County there is a separation into rudely parallel 

 ridges between Which are lowlands, which are utilized by the 

 southward flowing streams. East Du Page River and Salt 

 Creek. Near the south part of Du Page County the East Du 

 Page is forced to turn westward into the West Du Page, for the 

 ridges which are separate in Du Page County coalesce in north- 

 ern Will County. Salt Creek has, in its lower course, left its old 

 valley and cut a new one eastward through Proviso Township, 

 Cook County, to the Des Plaines. The old valley passes south- 

 ward through the western part of Lyons Township, almost in line 

 with the upper portion of Salt Creek Valley, crossing the Chicago, 

 Burlington and Ouincy Railway west of Western Springs, and 

 joining the Des Plaines about seven miles below the present 

 mouth of the creek. 



Through Will and southern Cook Counties the moraine has 

 a southeasterly course. Its inner border is nearly parallel \vith 



