193 



considerably more numerous in tlie belt than elsewhere. They are also 

 more numerous about the eastern ends of the sags or low valleys through 

 the Independence-Darlington moraine. They are very numerous in the 

 valley of the Wabash at Independence where the belt crosses the river. 

 Here in the lowest part of the valley, and on the terrace north of the 

 river, they lie so thick over the surface that a man might cross a field 

 stepping from one to another. The belt is not continuous, but there are 

 gaps both south and north of Independence. 



A number of theories to explain these bowlder belts has been pro- 

 posed. The theory which was in some way suggested to Mr. T. C. Cham- 

 berlin, that they are beach lines, was dismissed by him with scant 

 notice. His objections to the theory were that the slopes are all to the 

 southwest and that there could be no ponding of great extent in front of 

 the ice sheet. The general slope indeed is to the west, but the slopes 

 on which the bowlder belts lie are eastward slopes. Further, the belts 

 lie at the western side of areas that have been for considerable periods of 

 time covered with water. 



The belt southeast of Independence is conspicuously related to the 

 western border of such a lake area. The belt noi'thwest of the Wabash 

 follows quite closely the western curve of the border of the south arm 

 of Lake Kankakee, as mapped by Mr. Leverett.* 



This belt is not necessarily or probably a continuation of the belt 

 south of the Wabash River. Nor are the bowlders lying across the valley 

 at Independence certainly to be correlated with the belts to the north 

 and south. All the bowlders were probably deposited by floating ice, 

 at the western shallow edges of the lakes, where bergs and floe ice would 

 strand and drop their loads. They were deposited in the river valley 

 at Independence while the river was at that point the outlet of an ex- 

 tensive lake held in the deep preglacial valley extending upstream to the 

 mouth of the Tippecanoe River and of unknown width and extent. This 

 lake has since been filled by gravel deposits, but bei'gs stranding about 

 the outlet may have deposited the bowlders at the top of the terrace, 

 and they have since dropped to lower levels as the valley was cut deeper. 

 Reasons for believing that the ice sheet disappeared from the region to 

 the east of the present southward flowing course of the Wabash and 

 along the Tippecanoe River are stated in the article on "The Development 



*In his Monograph on the Illinois Lobe, pages between 24 and 25. 



