236 feature's AMracles* 



gan its southern journey this zone or climate 

 was moved, southward in front of the ice, thus 

 forming, as it were, a moving zone whose cli- 

 matic conditions were similar to those of the 

 arctic regions (at least so far as temperature 

 was concerned) in preglacial times. The ice 

 movement was so gradual that time was given 

 for forests to spring up in advance of it that 

 moved southward at about the same rate as 

 that of the moving ice. Undoubtedly the aver- 

 age movement was very slow and was probably 

 thousands of years reaching its southernmost 

 limit, which is now marked by the terminal 

 moraine. Thus it will be seen that while the 

 individual trees and plants could not move, 

 the forest as a whole could. It was gradually 

 being cut down on its northern limit and as 

 gradually it grew up on the southern limit of 

 the zone; the ice movement being so slow that 

 the young tree of to-day on the southern limit 

 becomes a full-grown king of the forest by the 

 time the relentless icebergs reach it and cut it 

 down and thus the process went on until the 

 plants, trees, and animals of the arctic region 

 were driven hundreds of miles south of the 

 great chain of lakes on the northern boundary 

 of the United States. 



Many of the animals of preglacial times 

 were unable to stand the strain of the ever- 

 changing climatic conditions and have become 

 extinct, but their fossil remains are left to tell 



