364 Glaciers. 



either hand, and should an extra steep descent occur 

 in its channel, as in the glacier of the Khone, the ice 

 becomes troubled and shattered, like a silent frozen 

 cataract, to re-unite below in a more tranquil sheet. 

 So also in the valley of Hinter Ehine, above the source 

 of the river, a tall cliff bounds the eastern side of the 

 Khine glacier, above which another large ice-sheet 

 presses to the edge of the precipice, from whence in 

 summer, constant avalanches, now here, now there, fall 

 with a sheer descent and a recurrent roar like that of a 

 great waterfall. 



All glaciers are traversed by cracks termed crevasses. 

 Now the mountain peaks that rise above tne surface of 

 a glacier are in places so steep that the snow refuses to 

 lie upon them, even when they may happen to be above 

 the limits of the average line of perpetual snow, so 

 that masses of rock being severed by atmospheric dis- 

 integration, constantly fall from the slopes and find a 

 temporary resting-place on the surface of the ice at 

 the margin of the moving glacier, and, as it were, 

 float upon its surface in long continuous lines ; for the 

 motion of a glacier is so slow, that the stones that fall 

 upon its surface are sufficiently numerous to keep up a 

 continuous line of blocks, earth, and gravel, often of 

 great width. In like manner if an island-like boss of 

 rock rises through the ice in the middle of a glacier, 

 a line of stony debris travels on the surface of the 

 glacier from the lower end of the island, which, often 

 buried in the winter's snow, becomes again exposed 

 during the heat of summer. These stones, when two 

 glaciers combine to form one stream of ice, as in the 

 lower glacier of the Aar, meet at the V-shaped angle 

 of junction, and form one grand line running down the 

 centre of the glacier (fig. 78). Such lines of debris, 



