76 Glaciers and Glacial Had iani s— Cla ypoh'. 
gla<;ier is a large snow or rain-fall. Without this the material 
will be lacking. The north-eastern portion of the continent is 
now a region of great precipitation and the same was true, so 
far as any eAndence to the contrary is concerned, at the time in 
((uestion , We must consequently look for great developement 
of ice in that region. In consonance with this is the testimony 
of the ice-printing on the rocks, which, speaking generally, ra- 
diates to the south-east, south and south-west from that district, 
that is from the area near Hudson's hay. That the ice wa* 
there verv thick is scarcely to be doubted. The evidence from 
the mountains of the north-east seems conclusive on this point. 
They wei'e apparently buried in ice. We need not perhaps go 
so far as some have gone and suppose that the ice-sheet was so 
thick as to move over them without any diversion. This is 
scarcely probable, liut all the phenomena point to a very great 
depth — probably greater than anywhere else in the eastern part 
of the continent. Westward however we fail to find proof of 
this great thickness. The south-westerly direction of the groov- 
ing of the rocks in that region indicates clearly enough that the 
How of the ice was off the Laurentian highlands toward the 
great lakes and the valley of the Mississippi. And that all this 
country was also buried in ice can not be disputed. Hut that 
the ice-sheet in the midland states Avas very enormously thick 
we have no evidence to prove. Indeed what evidence has been 
obtained looks in the opposite direction and tends to show that 
the thickness was small when compared with that of the north- 
eastern glacier. 
The massive glacier of Lower Canada and New England soon 
reached the Atlantic and its south-eastward advance was stopped 
by the water. Farther west the Laurentian ice felt the effect 
of the high ground of the Appalachian mountains which it was 
apparently unable to climb, and its southward progress was 
therefore arrested. But in the midland states these barriers did 
not exist and the striation shows that a vast extent of land in 
that direction was under an ice-sheet that traveled to the south- 
west. But that its thickness was not enormous seems evident 
from the fact that a large district in Wisconsin remained per- 
manently uncovered and is now known as a ''driftless area," 
showing none of those traces of ice-action that are so abundant 
in the surrounding country. 
