228 GEOLOGY OF ILLINOIS. 



that we cannot argue directly from their position with regard to the form of 

 the land at a later period, yet we may fairly infer that whatever channel then 

 existed probably had the aforesaid direction ; and, since no such depression 

 appears to exist, or to have existed toward the southwest, it probably did exist 

 to the eastward, and it is not impossible that old Lake Kankakee had its out- 

 *et by the Wabash, before its waters began to cut down the rocky barrier 

 through which they have since excavated the deep valley from Aroma to Wil- 

 mington. 



Though the sand ridges have not been traced to their limit on the upper 

 Iroquois, yet, as the bed of the river at Renssalaer, only sixteen miles from 

 the southernmost sand bed on the L., N. A. & C. R. R., is said to be only 

 thirteen feet higher than the top of that bank, it is evident that the old lake 

 must have nearly surrounded the high land of the southeastern part of Kan. 

 kakee county, and the northwestern part of Iroquois. The elevation of this 

 peninsula is known to me at only one point,* namely, at Morocco, Newton 

 county, Indiana, which Owen states to be one hundred and eighty feet above 

 the bed of the Kankakee at Momence. 



The peninsula between old Lake Kankakee and Lake Michigan varies from 

 ten to twenty-five miles in width, and is seventy or eighty miles long. The 

 lowest measured point is near Eagle lake, in Will county, Illinois, where CoL 

 Worrall's surveying party found an elevation of one hundred and seventy-three 

 feet above the established " datum " of " six feet below the lowest registered 

 water of Lake Michigan." Monee, a few miles west of this point, is two 

 hundred and twenty-eight feet above " datum," by railroad survey. It is 

 probable that a much lower point exists upon the "divide," somewhere near 

 Deep river or Salt creek, in Lake county, Indiana. A large sand ridge forms 

 the north shore of Eagle lake, at an elevation of one hundred and forty-eight 

 feet above " datum ; " but this is probably local, and not directly connected 

 with the ridges of the river valley. 



Much of all these sand accumulations is nearly pure quartz grain, partly 

 worn and rounded, as if by long wear and travel; while parts are evidently 

 merely the disintegrated sandstones of the Coal Measures, not much changed 

 by friction. 



For further details of elevations and distances, I must refer to the map 

 accompanying this report, for which the survey is originally and principally 

 indebted to the liberality of Mr. A. J. Mathewson, chief engineer of the Illi- 

 nois and Michigan canal ; though many levels have also been added from data 

 kindly furnished by Gen. J. H. Wilson, chief of the Illinois River Survey, and 



*The Chicago and Danville Railroad crosses this promontory, a short distance west of the 

 State line ; but applications for the profile of that road have been unsuccessful. 



