Problems, Middle Mississippi River Region, Pleistocene Time 227 
One of the most significant discoveries in the drift was the 
presence of blue hematite. It was first noticed among the peb- 
bles in the collection which Drushell had made from the St. 
Louis drift and had presented to the Department of Geology 
and Geography at Washington University. The pebble is about 
an inch and a half in diameter and of a type of blue hematite 
closely resembling that from the Lake Superior district. When 
Prof. Drushell was in St Louis, he kindly identified the label 
of the box containing the hematite as written by himself and 
the contents as collected near the Shaw School. 
In north St, Louis, in the area covered by Illinoian drift 
there appears in certain localities another drift usually under- 
lying the Ilinoian drift that has been described as pre-IIlinoian 
by some writers. Pebble analyses seem to accord with this view. 
But as previously stated, it is possible that this apparently older 
drift is merely a mixture of lower Illinoian drift and Lafayette 
gravel. At present there seems to be no positive evidence either 
Way. 
The pre-Illinoian drift in St. Louis has been ascribed 
by some to the Kansan ice sheet, by others to the Nebraskan. 
Drushell27 thought that both ice sheets might have been 
involved. The evidence at present available is not conclusive, 
although it doubtless favors the Kansan ice sheet as_ the 
source of at least some of the drift. The origin of much, if 
not all, of the drift seems to have been in the northwest, from 
the Kewatin center, as shown by the large number of purple 
quartzite boulders and the corroborating testimony of the blue 
hematite. It would appear entirely reasonable that a tongue 
from the ice sheet in Lincoln County, which certainly crossed 
the Missouri River, proceeded into St. Louis. Leighton?* is in- 
clined to correlate the drift on the bluffs at Alton with a tongue 
of ice moving in a northeasterly direction and there is evidence 
to support this and no direct evidence against it. On the other 
hand, it is possible that the St. Louis drift, or a part of it, 
represents the farthest southward advance of ice from the 
Kewatin center in Nebraskan times. More detailed evidence will 
be needed before the question can be finally settled. 
