[TYRRELL] PRESIDENTIAL ADDRESS 7 
south of it. The thick heavy beds of compact till which underlie 
the country south of the Bay are here tentatively ascribed to the 
influence of the last of these glaciers which is believed to have moved 
and kneaded up the previously existing marine deposits that had been 
spread out over the sea floor probably during the closing epochs 
of the Patrician or Keewatin periods. It is possible that the lower 
till on the Shamattawa river may have been formed by the Keewatin 
and the upper till by the Labradorean glacier, but two similar tills 
are found on Severn river, and other streams farther east, where they 
were probably both formed by two separate advances of the Labra- 
dorean glacier, so it is perhaps more probable that the two tills on 
the Shamattawa river were formed in the same way. 
Extra-glacial Lakes 
Lake Agassiz was the greatest of these. It was ponded in front 
of the coalesced faces of the Keewatin and Labradorean glaciers, and 
at various stages of its existence covered a great extent of Manitoba 
from the Churchill river southward to and beyond the International 
Boundary Line. In its higher stages it drained southward into the 
Mississippi river, but in its lower and later stages it would appear 
to have either drained northward into Hudson Bay along the edge 
of the ice sheet, or, as we shall see later, to have actually formed an 
arm of Hudson Bay. 
In the vicinity of Oxford and Knee lakes a body of water, which 
we may call Hyper-Oxford lake, appears to have been ponded in front 
of the retiring Labradorean glacier. The evidence of its presence 
consists of beds of sand and clay which lie around the shore of the lake, 
and rise about thirty feet above it. As the lake is 585 feet above the 
sea the summits of these sandy terraces would be approximately 615 
feet above the sea. They have every appearance of having been 
formed around a tongue of the glacier which filled the basin of the lake 
at the time. 
Chacutinow or The Hill, which rises 461 feet above Hill river 
at its foot, or 900 feet above the sea, is composed of fine, well rounded 
gravel, but it is probably an esker which has been formed near the face 
of the Labradorean glacier. 
Post Glacial Deposits and Elevation of the land 
As the climate ameliorated towards the close of the Glacial 
Period the ice of the Labradorean glacier melted away, and its front 
retired northward, while at the same time the land on which it had 
rested gradually rose. It is not yet known to what extent the land 
was depressed when the glacier covered the whole country south- 
Sec. IV, Sig. 2 
