A GEOLOGIC SPRING TIME. 275 



In such a tomb, they lay unchanged until the age of man 

 and slowly returning warmth brought their lifeless carcasses 

 to a dumb resurrection. 



The accumulation of five thousand feet of ice over a por- 

 tion of the earth's surface required some new adjustments of 

 equilibrium. If the ice-bed covered the entire north, and the 

 terrestrial crust remained rigid, the added weight transferred 

 the earth's center of gravity toward the north, and with it 

 flowed the ocean northward. With a flooding of all the 

 northern shores there was a corresponding emergence of the 

 antarctic. If the weight of ice depressed the terrestrial crust, 

 the position of the center of gravity may not have been 

 changed; but the shores depressed would be flooded by the 

 ocean, as before. Farther, the displaced fluid matter beneath 

 sought escape, through fissures, to the surface. If the enor- 

 mous ice-pressure was felt by the regions east of the Great 

 Plains and north of the Snake River, the depression of the 

 glaciated regions caused the fluid internal substances to react 

 beneath regions farther west and south ; and in many cases, to 

 develop fractures through which molten outflows took place. 

 In this view, the great post-pliocene lava floods of the west 

 were the counterpart of the great ice-burdens of the east and 

 north. 



. A GEOLOGIC SPRING 



INCIDENTS OF THE CHAMPLAIN EPOCH. 



THE rigor of the long winter began to relent. We can not 

 certainly state what physical conditions brought about the 

 change ; but if elevation brought the cold, then probably, the 

 return of warmth resulted from restoring the ancient level. 

 We are certain, on good evidence, that a subsidence took place. 

 At some time after the advent of general glaciation, the east- 

 ern United States and Canada were inundated by the ocean. 

 The depth of the submergence was 470 feet at Montreal ; 

 and it diminished gradually southward. At Lewiston, Maine, 

 the sea-beach is two hundred feet above present tide-level ; 



