THE OLD ICE-FLOOD 
it: as slow or slower than the hour-hand of the 
clock, yet an actual progression, carrying it, in the 
course of thousands of years, from its apex in 
Labrador well down into New Jersey, where its 
terminal moraine is still clearly traceable. 
A river of ice, under the right conditions, flows as 
literally as a river of water, fastest in the middle, 
and slowest along its margins where the friction is 
greatest. The old ice-sheet, or ice sea, flowed around 
and over mountains as a river flows around and over 
rocks. Where a mountain rose above the glacier, 
the ice divided and flowed round it, and reunited 
again beyond it. One may see all this in Alaska at 
the present time. Water, of course, flows because of 
its own pressure; so does ice, only the pressure has 
to be vastly greater. A drop of water on the table 
does not flow, but, pile it high enough, and it will. 
The old ice sea flowed mainly south, not because it 
was downhill in that direction, but because the 
accumulation of ice and snow at the North was so 
great. If through any climatic changes, the snow- 
fall were ever again to be so great that more snow 
should fall in winter than could melt in summer, 
after the lapse of thousands of years, we should 
have another ice age. 
