326 THE CANADIAN NATURALIST. [Vol. viii. 



temperature of the altitude to which it reached, render it im- 

 probable that it was several times wholly melted away. 



Near the end of the glacial period, we have proof that the sea 

 stood 100 to 200 feet higher than now along the coast of New 

 England, and about 500 feet above its present level in the valley 

 of the St. Lawrence. It seems quite probable that this submer- 

 gence was produced by the attraction of the ice, which, as pointed 

 out by Adhemar, would draw the ocean away from the equa- 

 tor towards the poles. The whole amount of water in the sea 

 was diminished ; but the accumulation of vast sheets of ice, 

 probably several miles in thickness, would be sufficient to retain 

 the ocean at its present height near their lower limits, while it 

 would rise much higher than now about the poles, and at the 

 equator would sink far below its present level. Such a rise of 

 the sea, increasing in amount in high latitudes, is attested by 

 the modified drift of both America and Europe ; and coral 

 islands afford proof of the corresponding deprcsssion of the 

 ocean, succeeded by a gradual elevation to its present height, 

 over large areas within the tropics. The two great continents 

 appear to have existed, with somewhat the same outlines as now, 

 from a very remote geological epoch. From the Silurian age to 

 the glacial period we have no record that any part of New 

 Hampshire was submerged beneath the ocean. This long stabi- 

 lity makes it more probable that these recent changes in the 

 relative heights of land and sea, are due to the cause which we 

 have explained, rather than to any downward and upward move- 

 ment of the earth's surface. 



Three divisions of Post-pliocene time are well marked in New 

 England, and apparently in all countries which have been over- 

 spread by ice. They are distinctly characterized as successive 

 periods of glaciation, deposition, and erosion. The first is the 

 glacial period, during which the ice-sheet prevailed, moving over 

 New Hampshire towards the south or south-east, as shown by 

 striae throughout the State. These glacial markings appear to 

 show the last direction in which the ice moved, since the latest 

 wearing necessarily effaced previous striae. We therefore learn 

 that the ice finally retreated from New Hampshire towards the 

 north-west and north, and from the region of the Great Lakes 

 and along the St. Lawrence valley towards the north-east. 



As the ice-sheet slowly advanced during this period, fragments 

 were torn from the ledges, and a large part of these were sooner 



