148 THE ILLINOIS GLACIAL LOBE. 



party of geologists near Long Grove in northern Scott County, and are 

 reported to occur for several miles farther east. Here also they occur on a 

 plain referred with some confidence to the Iowan stage of glaciation. Hav- 

 ing traced undoubted Iowan deposits to the border of the Mississippi, it 

 becomes a matter of interest to determine whether the Iowan ice crossed 

 into Illinois. 



The examination made by Mr. Hershey and the writer in Whiteside 

 and Carroll counties, directly east from the district just discussed, brought 

 to light several features of a puzzling nature, some of which may have 

 direct bearing- upon this question. These features fall into five classes, (1) 

 fresh till; (2) a tract free from loess; (3) a sand border east of the fresh till; 

 (4) a loess apron outside the sand border; (5) ridges of loess with similar 

 trend to the paha of the Iowan drift area. Certain other features found in 

 southern Whiteside and northwestern Henry counties are considered in con- 

 nection with the probable extension of the Illinois lobe at the Iowan stage. 

 The features here considered lie outside the probable limits of that lobe. 



Deposits of fresh-looking till occur on the elevated upland about 10 

 miles due east of the north part of Clinton, near the south line of sec. 13, 

 LJstick Township, and near the west end of the line of sees. 18 and 19, 

 Clyde Township, Whiteside County. The till has a yellowish-gray color 

 similar to that of the Iowan near Polo, in Ogle County, and effervesces at a 

 depth of less than 2 feet from the surface of the ground. As the exposures 

 occur in the midst of a tract nearly free from loess, there is nothing to 

 protect the till from leaching. It is in marked contrast to numerous other 

 till exposures in the immediate neighborhood, which show decidedlv stronger 

 surface stain and are leached to a depth of 5 or 6 feet. These exposures 

 of fresh-looking- till were visited by Calvin, Udden, Bain, and the writer in 

 November, 1897, and by all were recognized to present a much fresher 

 appearance than the surrounding exposures. It was also recognized that 

 advantages for erosion here seem no greater than at points where a stained 

 and deeply leached surface is presented. Although several different lines 

 have been traversed by Hershey and the writer in Carroll and western 

 Whiteside counties, no other exposures of such fresh till have been noted 

 outside of the possible limits of the Iowan sheet formed by the Illinois lobe. 

 These exposures, it will be observed, occur within the limits of a single 

 square mile. Taken by themselves they seem a weak, though perhaps not 



