96 THE CANADIAN NATURALIST. [Vol. vi. 



during tlie process of boring. The ratio of increase in tempera- 

 ture obtained by observations in this tunnel was one degree for 

 every one hundred feet of descent — a rate which is probably 

 nearer the truth than that first named. Prof Tyndall found the 

 winter temperature of a glacier in the Alps examined by him, at 

 its surface, to be 5'^ Cent. (23^ Fahr.) If we assume that the 

 temperature of our supposed Acadian glacier at its surface was 

 fifteen degrees lower, and the conductive power of ice only one- 

 half that of solid rock, the heat communicated from the interior 

 of the earth, even at the low rate observed at Mount Cenis, would 

 if the glacier were 5000 feet thick, raise the temperature at its 

 base above the freezing point. It may readily be perceived that 

 this agency would exert a momentous influence on deeply buried 

 glacial iee, converting it into that spongy mass of intimately 

 mingled ice and water which helps to give the glacier its river- 

 like flow. It may also be inferred, if the relative elevation of 

 the land in different parts of New Brunswick was the same in 

 glacial times as now, that as the glacier did not exceed 5000 feet 

 in thickness the slope of its surface from the Bay Chaleur to the 

 Quaco Hills, could not have been more than one-third of a degree 

 and gravitation could have exerted very little force in pushing it 

 on to the south over this part of its path. Unless the Lauren- 

 tide Hills stood at much greater elevation then than now, and of 

 this we have no evidence, this part of the glacial sheet (if such 

 existed) must have been a great lake of ice, having no perceptible 

 motion. 



Glacial Erosion. — A great amount of erosive power has been 

 attributed to glaciers, more perhaps than their known action in 

 Alpine regions will warrant. From an address of Sir R. S. 

 Murchison (this Journal, Feb. 1864), it maybe inferred that the 

 glaciers observed by him in the Alps have not the power of push- 

 ing out before them even the beds of sand and gravel which lie 

 in their paths, and in some cases scarcely of disturbing the sur- 

 face of the ground. He cites an instance observed by Mr. Yon 

 Der Linth, in which a glacier actually forms a bridge over a nar- 

 row gorge in the valley through which it moves. These features 

 in the Alpine glaciers may pethaps be explained upon the grounds 

 taken by Prof. Tyndall in discussing the influence of pressure in 

 reducting the melting point of ice in the glaciers. He very justly 

 infers that the thrust of a glacier is very materially reduced by 

 the obstacles which it encounters in its progress down the mountain 



