STELE WITHIN LIMITS OF SHELBYV1LLB MORAINE. 415 



the Illinois lobe. . A careful examination of the striated surface failed 

 to disclose decisive evidence whether the movement was northward or 

 southward. It may be remarked in this connection that just above the city 

 of Logansport the bed of Eel River shows heavy glacial grooves bearing 

 S. 58° W., which are evidently the product of the movement from the 

 Lake Erie Basin. It seems scarcely possible for the same ice movement to 

 produce, within the limits of a single township, striae with bearing differing 

 108 degrees, and that too in a comparatively smooth region. But so little 

 is known as yet concerning' the possibilities of ice movement, that judgment 

 should perhaps be reserved. ■ 



The stria? of northeastern Illinois show some interesting deviations from 

 a general southwestward course. In the Des Plaines Valley there is a range 

 from S. 18° W. to S. 96° W. Three observations between Summit and 

 Lemont show bearings S. 34° W., S. 18° W., and S. 60° W. The striae 

 bearing nearest westward are accompanied by heavy g-rooves which seem 

 to call for the action of a thick ice sheet, but the other exposures show only 

 faint striation, and it has occurred to the writer that possibly this faint 

 striation is attributable to masses of ice floating down the valley after the 

 ice sheet had withdrawn. Another locality in northeastern Illinois, where 

 the striation is thought to be referable to floating ice, is on the bluff of Fox 

 River, north of Millington, in Kendall County, where faint striae occur with 

 bearings ranging from S. 9° 30' E. to S. 27° 30' W. In a great majority of 

 exposures in the Illinois district glaciation is heavy, with complete planing 

 of surface and often with heavy g'rooves, and can scarceh- be referred to 

 floating ice. 



At Joliet striae were observed with bearing slightly north of west, but 

 this bearing is almost at right angles with the trend of the Minooka till 

 ridge a few miles west of Joliet, and is probably referable to the ice move- 

 ment which produced that ridge. The same explanation j:>robably should be 

 given for the bearing 20° north of west, shown in an exposure a few miles 

 west of Aurora (sec. 1, T. 37 N., R, 6 E.), for a moraine with NE.-SW. 

 trend passes through the district immediately northwest of these striae. 



On Stony Island, in the south part of Chicago, the rock quarry where 

 glaciation was observed has beds which dip toward the southeast with an 

 angle of 30 degrees or more. Heavy scorings follow the line of strike, with 



