416 GEOLOGICAL CHANGES. 



For 450 miles he sailed in front of this cliff, and found it 

 unbroken by a single inlet.* 



We can form some idea of this great ice sheet by what 

 we know of the interior of Greenland, which also is covered 

 by a continuous ice sheet, sloping gradually towards the 

 interior. Even of this ice sheet we know little beyond the 

 edge. Dr. Hayes, who has penetrated further inland than 

 any one else, in describing his camp at the furthest point he 

 reached, about seventy miles from the sea, says : " Our station 

 was as sublime as it was dangerous. We had attained an 

 altitude of 5000 feet above the sea-level, and were seventy 

 miles from the coast, in the midst of a vast frozen Sahara, 

 immeasurable to the human eye. There was neither hill, 

 mountain, nor gorge anywhere in view. We had completely 

 sunk the strip of land between the Mer de Glace and the sea, 

 and no object met the eye but our feeble tent, which bent to 

 the storm. Fitful clouds swept over the face of the full- 

 orbed moon, which, descending towards the horizon, glim- 

 mered through the drifting snow that scudded over the icy 

 plain to the eye in undulating lines of downy softness, to 

 the flesh in showers of piercing darts." (Open Polar Sea, 

 p. 134.) 



In fact, the ice sheet must slope upwards towards the 

 interior, because the snow which falls there would accumulate 

 until it reached an angle sufficient to carry it towards the 

 sea. In Greenland, the slope, so far as observed, appears to 

 be about 2. Prof. Hopkins has shown that ice barely 

 moves on a slope of one degree. This minimum slope of 1 

 continued over the 1400 miles from the edge of the Antarctic 

 ice cap to the South Pole, would give a thickness of ice at 

 the Pole of no less than twenty-four miles. But even if the 

 slope is only J degree, and, as Mr. Croll points out, we have 

 no evidence that such a slope would be sufficient to discharge 



* Geikie's Ice Age, p. 101. 



