LAKE KANKAKEE. 331 



The west border of the Iroquois sand area follows nearly the north 

 flowing - part of Iroquois River northward to northern Iroquois County, and 

 there swings eastward along Beaver Creek Valley, crossing the Marseilles 

 moraine between St. Anne and St. Mary, and thence extending both east- 

 ward and westward into the Kankakee Basin. 



As noted above, the sand is continuous along the south border of the 

 Kankakee to Grundy County, and thence westward along the Illinois to 

 the borders of the Marseilles moraine. The north border of the sand 

 follows the low bluff on the north side of the Kankakee from Will County, 

 Illinois, eastward to the head of the Kankakee, where the tracing began. 



It will be observed that this sand-covered district occupies not only a 

 large part of the watershed of the Kankakee but also a part of the Tippe- 

 canoe watershed. It embraces an area of approximately 3,000 square 

 miles, in which sand deposits are nearly continuous. To this about 300 

 square miles should be added to extend the area to the extreme limits of 

 the sand ridges. 



RANGE IN ALTITUDE OF THE BORDER OF THE SAND. 



At the eastern border plane-surfaced deposits of sand and also of 

 gravel occur up to an altitude of about 750 feet, and dunes are found on 

 the moraine at an altitude of fully 800 feet above tide. Along the south 

 border the altitude of the sand ridge ranges from 700 feet or less at the 

 Tippecanoe River to about 750 feet in Cass County and in western White 

 and northern Benton counties. The altitude decreases upon passing west- 

 ward from Benton County, the highest sand deposits in western Iroquois 

 County, Illinois, being about 675 feet, and the outlet from the Iroquois to 

 the Vermilion across Ford County scarcely 650 feet. The highest well- 

 defined beach along the Illinois in the Morris Basin is but 560 feet. On the 

 north border of the Kankakee marsh the altitude decreases from 750 feet 

 or more in western St. Joseph County, Indiana, to about 650 feet at the 

 State line and 570 feet at the mouth of the river. In general there is a 

 westward descent in the sand-covered area, the only prominent exception 

 being a depression in the southeast part on the borders of the Tippecanoe 

 River. The outer sand ridge there stands fully 50 feet lower than 20 miles 

 west at the line of White and Benton counties. The outer ridge is main- 

 tained continuously up this grade of 50 feet, from Remolds to the Benton 



