26 The American Geologist. juiy, iggi 
It is generally more or less distinctly stratified and at its base in 
man}' places contains transported boulders. It also forms the 
north shore of the lake as far westward as the base of the sand spit 
that bounds Limestone ba}' on the south. The western side of 
the lake has not yet been sufficiently examined to say to what 
extent the older deposits are there covered with alluvium. 
In the western portion of the lacustral basin Prof. Hind re- 
marked as long ago as 1859, speaking of the "Big Ridge of the 
Assiniboine " which has been called by 3Ir. T'pham the Ossowa 
beach, that ' ' between this ridge and the xVssiniboine the land is 
eminently rich and fertile ; be3'ond the ridge north, it is described 
b}- the half-l)reeds as wooded, sandy and poor. "* Around lake 
Manitoba and Wiunpegosis, there is comparatively little alluvium, 
the country in many places being immediately underlain by till. 
Lake Agassiz. 
In the absence of any evidence of a land barrier to the north 
and east sufficiently high to hold back the waters of the lake whose 
receding shore lines are marked by the beaches mentioned above, 
Mr. Upham has suggested that the water was held between the edge 
of the receding glacier of the Winnipeg valley and the Manitoba es- 
carpment, and to this body of water he has given the name lake 
Agassiz. As to the extent of this lake south of the present 
southern shores of lakes Manitoba ahd Winnipeg, nothing can be 
added at present to what is given by Mr. Upham in his recent 
report to the Canadian Geological Surve}'. Of the lacustral re- 
gion ver}' little evidence was at hand, and the generalizations from 
that evidence were clearly of a prelitninar}' character. 
Instead of assuming that lake Agassiz at any time covered an 
area of 110,000 square miles, as stated b}' Mr. Upham, let us 
consider the h3-potliesis that it was never at any time of enor- 
mous size, but rather that it was a belt of water, say as wide as 
lake 3Ianitoba now is, lying along the foot or edge of the glacier 
and quite possil)ly with a large expansion towards the south. 
Under this hj'pothesis the lacustral area was covered with the 
Manitoba glacier while all the more elevated beaches were being 
formed, and how far south this glacial lobe extended at any par- 
ticular time it is impossible to say, since its foot was washed by the 
waves of the lake, and the coarser morainic material that dropped 
^Papers relative to the exploration of the eountry between lake Sup- 
erior and till' Ucfl rivfi- ><(>ttlenient, page 10(5, folio London, Gov., 1859. 
