224 Transactions of the Academy of Science of St. Louts 
and for several blocks east therefrom, but not westward (Figs. 
20 and 21). L. M. Dougan, Principal of the Eugene Field Public 
School, called the writer’s attention to an excavation being made 
at the Corner of Taylor Avenue and Olive Street. This excava- 
tion showed the presence of pre-Illinoian drift. 
It has been possible to interview some individuals who saw 
the relatively recent excavations for the United States Postoffice 
at Market and Eighteenth streets, and for the Southwestern Bell 
‘Telephone Building at Pine and Eleventh streets. Those who 
had seen these excavations described gravels overlying the lime- 
stone bed rock and the descriptions fitted those of the pre- 
Illinoian drift very precisely. At the Southwestern Bell Tele- 
phone Building the drift was about two or three feet in thick- 
ness. At the Postoffice, the drift was thin at the northern end 
and thickened rapidly to the south to the unusual thickness of 
18 feet. This.is the general direction of the Mill Creek valley. 
The surface of the bed rock slopes in the same direction. 
The pre-Hlinoian drift in St. Louis is composed of a very 
stiff, dark reddish or brownish clay, sprinkled thickly with peb- 
bles and cobbles, and with occasional boulders. It has been 
described as a blue clay by some, but the typical exposure of 
the reported blue clay has long since been covered. The thick- 
ness varies from two to a reported eighteen feet. Most of the 
exposures in the city of St. Louis seen by the writer hardly 
exceed eight feet in thickness. 
The pebbles are predominately of chert, as shown by numer- 
ous pebble analyses (Table III). Quartzite is easily the next 
in abundance. Many of the quartzite pebbles and cobbles, and 
most of the quartzite boulders, have a reddish or purplish color, 
and many are banded in such a way as to closely resemble typical 
Baraboo quartzite. If the drift ever contained any limestone 
or dolomite pebbles, they have long since been completely re- 
moved by leaching. Not a calcareous pebble has been found by 
the writer in any pre-Ilinoian drift in St. Louis. 
