218 Transactions of the Academy of Science of St. Louis 
cretions like the loess-menschen are found. This appears to be 
the thickest and most extensive deposit of typical Illinoian till 
in St. Louis or St. Louis County. 
The general character of the till, from north of Chain-of- 
Rocks to O’Fallon Park, has caused every investigator, including 
the present one, to correlate it with the Illinoian drift directly 
across the river. Studies of the position of this ice front in 
Madison and St. Clair Counties, Illinois, indicate that this drift 
is closely associated with that found between Edwardsville and 
Caseyville. Pebble analyses are clearly in accord with this view. 
PRE-ILLINOIAN DRIFT IN ILLINOIS 
Bell and Leighton's have reported pre-Illinoian drift in sev- 
eral localities in Illinois, including, a particularly significant one 
in the vicinity of Winchester, where two different stream- 
cut banks expose three successive layers of till, proving beyond 
doubt the existence of both Nebraskan and Kansan till in Illi- 
nois. The writer visited the spot, sampled and photographed 
the exposure on Little Sandy Creek (Fig. 18). The top of the 
oldest till is highly altered, but it is recognizable as till. 
MacClintock'® sampled and made pebble analyses of the pre- 
Illinoian drift from many localities in Illinois, and came to the 
conclusion that the Kansan drift was from the Labradorean 
center and the Nebraskan drift from the Kewatin center. In a 
map in his article, he indicated that it was his opinion that a 
pre-Ilinoian drift found in St. Louis is of Kansan age from 
the Labradorean center. Analyses made in this study are not 
in accord with this opinon, but indicate a Kewatin source. 
In 1921, Leighton’? described a drift deposit in the quarries 
in the Mississippi River bluffs at Alton, Illinois. He described 
the drift as from one to three feet in thickness, considerably 
weathered, and containing calcareous concretions in which 
earlier investigators had found several mamalian fossil frag- 
