230 GEOLOGY OF ILLINOIS. 



nel is rather narrow, rock having been found upon its east side and south of 

 the Kankakee, within seven miles of Momence; the exact location of its 

 eastern bank is as yet unknown. From this point, the course of the channel is 

 not certain ; but it probably keeps near the State line until it nearly or quite 

 reaches the valley of the Iroquois, then runs westerly to the valley of Spring 

 creek, having a depth of one hundred and sixty feet near Sheldon (as reported 

 by H. S. Wing, Esq., of Kankakee City), and then turns south with a depth 

 of two hundred and sixty-eight feet between Onarga and Gilman, of " over 

 four hundred feet" between Onarga and Spring Creek Station, and of " over 

 three hundred feet" between Paxton and Rantoul, as reported by John Faulds, 

 Esq., of Catlin, Vermilion county. As the western bank was found at Chats- 

 worth, Livingston county, with its top eighty-eight feet, and its bottom two 

 hundred feet below the surface, thus giving a width of fifteen miles or more, it 

 is evident that the softer materials of the Devonian, Sub-carboniferous, and 

 Coal Measure shales and sandstones have afforded less resistance to the denud- 

 ing agent than the solid Silurian limestones, which confined it to less than 

 seven miles at Momence. Champaign and Onarga, in Champaign county, are 

 located over this old channel, and from one hundred and seventy-five to two 

 hundred and twenty-five feet above its floor ; but are probably near its eastern 

 border. Here and at Chatsworth we find, among the Drift beds, a single layer 

 of old mucky soil, with leaves and trunks of trees. At Bloomington, in Mc- 

 Lean county, the channel is two hundred and fifty feet deep, and the beds 

 which fill it include two beds of old soil, which I am inclined to accept as 

 indications that this point is near the middle of the old valley, or at least near 

 it principal channel. The route west of Bloomington is unknown. 



As the bluffs which bound the DuPage valley, upon the west, are composed 

 entirely of Drift gravel and clay, with a rock foundation nearly on a level with 

 the rock at the head of the Illinois, or about ninety feet below the present level 

 of the lake, while there is an elevated rock island reaching from there to Mo- 

 mence, it is not impossible that, in that region, also, there was at this same 

 period some outlet for the contents of the basin of Lake Michigan ; but no 

 deep, strongly-marked channel is there indicated. 



Rock Formations. 



Though great quantities of fragments of black shale, with not infrequent 

 rounded lumps of coal, are found in the Alluvial and Drift deposits, and con- 

 tinually excite the imaginations of persons ignorant of geology, no beds of 

 either coal or black shale exist within the county, except on its extreme west- 

 ern border. These fragments are either the remnants of beds which formerly 

 existed here, or, more probably, are remains of the beds which formerly con- 



