492 The American Naturalist. [June, 
tario. and thence to the east of Oswego, but no further trace- 
able, as the lake bottom rose to the northeast. Upon the 
southern side there was a series of escarpments (some now 
submerged), with vertical cliffs facing the old channel. By 
recent studies of the elevated beaches, it is demonstrated that 
the disappearance of this valley is due to subsequent warp- 
ings of the earth's crust, and that the valley of the St. Law- 
rence was one with that of Lake Ontario. Recent discoveries 
of a deep channel upon the northern side of Lake Ontario (a 
few miles east of Toronto), and of the absence of rocks to a 
great depth under the drift, far beneath the surface of Lake 
Huron, between Lake Ontario and the Georgian Bay — and in 
front of the Niagara escarpment, between these lakes — of a 
channel in Georgia Bay, at the foot of the escarpment, and of 
the channel across Lake Huron, also at the foot of a high 
submerged escarpment, show that the ancient St. Lawrence, 
during a period of high continental elevation, rose in Lake 
Michigan, flowed across Lake Huron, and down Georgian Bay 
and a channel, now filled with drift, to Lake Ontario ; thence 
by the present St. Lawrence valley to the sea, receiving on 
its way the ancient drainage of the Erie basin and other 
valleys. 
Origin of the basins of the Great Lakes. The two ques- 
tions involved are the "origin of the valleys " and the " cause 
of their being closed into water basins." The basins of Lakes 
Ontario and Huron are taken for consideration. The previous 
paper, upon the course of the ancient St. Lawrence, shows 
that the Huron and Ontario basins are sections of the former 
great St. Lawrence valley, which was bounded, especially 
upon the southern side, by high and precipitous escarpments, 
some of which are submerged. Upon its northern side there 
were lesser vertical escarpments, now submerged, with walls 
facing the old valley. The valley was excavated when the 
continent was at a high altitude, for the eastern portion stood 
at least 1,200 feet higher than at present, as shown by the 
channels in the Lower St. Lawrence, in Hudson's Straits, and 
off the New York and Chesapeake Bays. The valley was 
obstructed in part by drift and in part by a north and north- 
eastward differential elevation of the earth's surface, due to 
terrestrial movements. The measurable amount of warping 
defied investigation until recently, but it is now measured by 
the uplift of the beaches and sea cliffs. Only one other ex- 
planation of the origin of the basins need be considered — that 
of the " Erosion by Glaciers," {a) because the lake basins oc- 
:iated regions ; (^) glaciers are considered (by sorne) 
{c) supposed necessity, as the terrestrial warping 
not known. 
'Zt 
