264 IN AUTUMN. 



walked to and fro over the frozen Delaware, 

 where it reaches a full mile in width, and saw 

 at the time many horses and sleighs passing 

 from shore to shore. I recalled, as I walked, 

 what the geologists have recorded of the river's 

 history, and it was no wild whim of the un- 

 checked imagination to picture the Delaware as 

 a still more firmly frozen stream ; so firmly ice- 

 bound, indeed, that the mastodon might pass 

 in safety over it not cautiously, even, but with 

 the quick trot of the angry elephant and picture 

 still further a terror-stricken Stone-age hunter 

 fleeing for his life. 



Just as our brief yearly winter gives way to 

 milder spring, so, as the centuries rolled by, the 

 mighty winter of the Ice age yielded to changes 

 that were slowly wrought. Century by century, 

 the sun's power was exerted with more telling 

 effect ; constantly increasing areas of northward- 

 lying land were laid bare, and the forest followed 

 the retreating glacier's steps. This great but 

 gradual change had, of course, its influence upon 

 animal life, and many of the large mammals that 

 have been named appear to have preferred the 

 cooler to the warmer climate and followed the 

 ice-sheet on its northward march. 



In the unnumbered centuries during which 

 these changes came about, man increased in wis- 

 dom, if not in stature, and the rude implements 



