286 Canadian Record of Science. 
CONCLUSIONS. 
In summing up the conclusions of this paper it may be 
said : 
That glaciers, whilst contributing some results, had not 
much effect in eroding the lake basins proper, or in shaping 
the present general outlines. 
That the superficial deposits are the accumulations of 
denudation during immense periods of time since the Car- 
boniferous and earlier eras, and are not to be specially 
credited to the operation of glaciers. 
That Lake Superior is the most ancient of the lakes, dating 
its origin as far back as Cambrian, Keweenawan and 
Huronian times; that it is, in part at least, a synclinal 
trough, that volcanic action has had most to do with its 
origin and the shaping of its coasts; that its early outlet 
was through the depression in Whitefish Bay and that its 
waters joined the great pre-glacial river system at or near 
the Straits of Mackinac. 
That Lakes Michigan, Huron and Ontario were originally 
the bed of a pre-glacial river which first crossed the Ontario 
peninsula along the Niagara escarpment, and afterwards was 
diverted to a course by way of Long Point, on Lake Hrie and 
the Dundas valley ; that their basins were largely defined by 
the elevation of the Niagara and Hudson River escarpments, 
and in more recent times by warping of the strata and deposit 
of superficial sands and clays which blocked the old river 
channels and resulted in the lake basins retaining their 
water on the final elevation of the land to its present 
general levels. 
That the pre-glacial river system expanded in time into 
smaller lakes in each of the present basins of Lakes Michi- 
gan, Huron, Erie and Ontario. 
That Lakes Erie and St. Clair are the most recent of 
the lakes, and have at one time been more closely united, 
and that the formation of this united lake was due to the 
blocking of the old outlets both by superficial deposits and 
warping of the strata, and to the water being thus retained 
