276 Canadian Record of Science. 
perhaps be found on the upper peninsula of Michigan, but 
much less pronounced in character, as the strata there have 
not been elevated to the same extent. Finally, there are 
the fractures which afford the entrance to Green Bay, and 
those which constitute the various bays around the whole 
front of the escarpment. 
Now, these different facts are not mere accidental oc- 
currences, and their conformity to each other is not a mere 
coincidence. They show that the oscillations of the earth’s 
crust in this particular area, covering the State of Michigan, 
the larger part of Lake Huron, and the immediate country to 
the east of Lake Huron, and to the west of Lake Michigan 
have, from the Trenton period and probably earlier, been 
of a peculiar nature. These oscillations were confined to 
this area, and the forces which gave rise to them appear to 
have operated in conformity, in a general way, with the 
curved outline of the area and towards its centre. It is im- 
possible to ascribe to glacial forces the varying directions 
of the outcrops of the different formations within this area, 
from the Trenton to the Carboniferous, nor do the glacial 
strize or the alleged directions taken by the glaciers suggest 
it. It is most reasonable to assume that this area, located 
as it is close to Lake Superior, where during Huronian and 
Keweenawan or probably later times were vast volcanic 
eruptions, has been subject to repeated oscillations in level 
around a central area. That these oscillations have con- 
tinued to more recent periods is shown by the uplifting, 
west of the longitude of Hamilton, of the Niagara escarp- 
ment with its face always away from, whilst the dip is 
towards, the central area of the State of Michigan or of Lake 
Huron, as well as by the depression and re-elevation of this 
whole area when the present superficial clays were laid 
down. 
That the Niagara rocks did notextend much farther north 
of their present position near the southern coasts of Lake 
Ontario, nor much farther eastward than the escarpment be- 
tween Lake Ontario and the Georgian Bay, is shown by the 
present general position and direction of these and the 
