208 Transactions of the Academy of Sctence of St. Louts 
Nebraskan till can be developed. The single sample of drift 
that was believed to be of Wisconsin age was collected in St. 
Charles County, Missouri, in a unique position and showed a 
marked variation in composition from either the [llinoian or the 
pre-Illinoian samples. It is referred to later. 
THE WISCONSIN DRIFT 
The nearest approach of the Wisconsin ice sheet to the 
Middle Mississippi River Region was in the vicinity of Peoria, 
Illinois, which is approximately 100 miles from the northern 
boundary of the region. A tongue of ice from the Iowa ice 
sheet, which is now classified as the earliest sub-stage of the 
Wisconsin, crossed the Mississippi River a short distance north 
of Davenport, Iowa. This point is about 250 miles north of 
the northern boundary of the region. It may be seen that the 
effects the Wisconsin ice sheet would have had on the region 
would have been only indirect, through water-transported 
material. 
THE ILLINOIAN DRIFT IN ILLINOIS 
The writer has re-examined the till in the Middle Mississipp1 
_ River Region. The probable location of the various ice fronts 
near St. Louis is shown in Figure 14. At Edwardsville, Madison 
County, Illinois, a section of the drift is well exposed in the 
overburden of the shale-pit of the Alton Brick Company. This 
section is shown in Table IV. Particular attention is called to 
the stratified character of the upper ten feet of the drift. 
From Edwardsville northwestward, the elevation of the sur- 
face on which the drift rests decreases and the thickness of 
the drift also decreases. About four miles northwest of Edwards- 
ville, near Wanda, a glacial gravel characteristic of a frontal 
apron, or outwash plain, can be observed at an elevation of 
430 feet. From Wanda to Alton no drift was observed in any 
cuts; but in several localities sand and some deposits of blue 
clay appear to have been formed by water transporation from 
the drift. 
