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. 



