268 Canadian Record of Science. 
The two peninsulas which defend the entrance to Green 
Bay are formed of the Niagara limestones which here curve 
to the south-west, and at Burnt Bluff and neighbouring 
points on the west side of the northern peninsula rise into 
an escarpment facing however to the north-west and west. 
Whilst at the base of this escarpment the water is, as arule, 
comparatively shallow, the western side of the headland of 
the southern peninsula and of the adjacent islands carries 
deep water close to the shore, showing that the escarpment, 
continuing there, is in part, subaqueous, and faces also the 
north-west and west. It is important to observe these 
directions. Green Bay is however relatively shallow. The 
100-foot line encloses a very limited area which, on the 
northern side, extends in a narrow, river-like prolongation, 
into Little Bay de Noquette, giving color, to that extent, to 
the possibility which Winchell has suggested, that in pre- 
glacial times there was a connection between the Lakes 
Superior aud Michigan basins by this bay and the Whitefish 
and Chocolate Rivers. 
On the eastern side of the lake, Grand Traverse Bay in 
its upper half is divided by a long, narrow isthmus into two 
bays, each about twenty miles in length, and from one to 
two miles in width, with a general direction somewhat west 
of south. Though the outer bay which rests on the black 
shales has an average depth of 180 feet, these two inner 
bays are in reality narrow but abrupt and deep depressions 
varying in depth, in the one case, from 300 to 448 feet, and 
in the other from 300 to 612 feet. The lake bottom here is 
either clay, sand or rock. Lying almost parallel with these 
depressions are on the one side the long narrow lake known 
as Torch Light Lake, and on the other, the promontory 
which separates Grand Traverse Bay from the lake, and 
presents high bluffs on the western side. Originally these 
depressions were great fractures in the Devonian rocks, 
created by the elevation of the land here, just as the 
Niagara escarpment has been similarly fractured. 
Between the Beaver Island group and the Manitou Islands 
is another extensive preglacial depression, in the rocky 
