90 TI> i' American Geologist. f.-i>. ism 
of the western end of the lake have been recorded by Prof. T. 
Sterry Hunt"', and prove the existence of similar buried channels. 
The original recognitionf of the valley-like character of the ba- 
sins of Ontario and Erie was based upon the above-mentioned 
characters, and upon others now supplemented b} r a more perfect 
collection of facts ; but the greatest difficulty was in the occur- 
rence of the rock-bound outlet of lake Ontario, a difficulty which 
observations have at last dispelled, as will be seen later on. 
4. Features of the Huron basin. 
The southern half of lake Huron is a plain traversed by valleys 
and submerged to form only a shallow lake. Northward of this 
shallow basin, and extending obliquely across the lake for ninety 
miles, there is a submerged escarpment rising to a hight of from 
300 to 450 feet, facing north-eastward. The deeper part of the 
lake then trends northward in the direction of Georgian bay. At 
one point the extreme depth of the submerged valley reaches 750 
feet. The absolute depth of the rock in the deepest channel be- 
tween lake Huron proper and Georgian bay is not known, but 
soundings show 306 feet ; and as there is a deep channel upon the 
western side of Georgian bay it becomes highly probable that a 
deeper and connecting channel is filled with Drift, like those 
known to occur elsewhere, beneath the lakes. From the straits, 
between the islands, the narrow channel in Georgian bay, just 
referred to, extends south-eastward and is submerged to a depth 
of 510 feet. This is at the foot of the Niagara escarpment, 
which extends, as a strong topographic feature, from the head of 
lake Ontario, and, rising in places to 1,700 feet above the sea, 
into the peninsula between Georgian bay and lake Huron proper. 
The channels at the foot of escarpments, submerged or otherwise, 
in lake Huron and Georgian bay are fragmentary records of the 
history of the lake valley st. 
5. Features of lake Michigan. 
This lake is divided into two basins. The more northern and 
larger basin has a maximum depth of 864 feet. It is, in part, 
bounded by vertical submerged escarpments, one of which, upon 
*See Report Geol. Canada, 1863-66. 
fSee " Discovery of the Preglacial Outlet of lake Erie," etc. 
jSee U. S. Lake-Survey chart of lake Huron, and tin- Canadian 
chart of Georgian bay. 
