ICE AND GLACIERS. 107 



If the snow bridges are thick enough, they will support a man ;. 

 but they are not always so, and these are the places where men, 

 and even chamois, are so often lost. These dangers may readily 

 be guarded against if two or three men are roped together at 

 intervals of ten or twelve feet. If then one of them falls into a 

 crevasse, the two others can hold him, and draw him out again. 



In some places the crevasses may be entered, especially 

 at the lower end of a glacier. In the well-known glaciers of 

 Grindelwakl, Kosenlaui, and other places, this is facilitated 

 by cutting steps and arranging wooden planks. Then any one 

 who does not fear the perpetually trickling water may explore 

 these crevasses, and admire the wonderfully transparent and 

 pure crystal walls of these caverns. The beautiful blue colour 

 which they exhibit is the natural colour of perfectly pure water ; 

 liquid water as well as ice is blue, though to an extremely small 

 extent, so that the colour is only visible in layers of from ten to 

 twelve feet in thickness. The water of the Lake of Geneva and 

 of the Lago di Garda exhibits the same splendid colour as ice. 



The glaciers are not everywhere crevassed ; in places where 

 the ice meets with an obstacle, and in the middle of great glacier 

 currents the motion of which is uniform, the surface is perfectly 

 coherent. 



Fig. 17 represents one of the more level parts of the Mer de 

 Glace at the Montanvert, the little hoiise of which is seen in the 

 background. The Gries Glacier, where it forms the height of 

 the pass from the Upper Rhone valley to the Tosa valley, may 

 even be crossed on horseback. We find the greatest disturbance 

 of the surface of the glacier in those places where it passes 

 from a slightly inclined part of its bed to one where the slope is 

 steeper. The ice is there torn in all directions into a quantity 

 of detached blocks, which by melting are usually changed into 

 wonderfully shaped sharp ridges and pyramids, and from time to 

 time fall into the interjacent crevasses with a loud rumbling 

 noise. Seen from a distance such a place appears like a wild 

 frozen waterfall, and is therefore called a cascade ; such a cascade- 

 is seen in the Glacier du Talefre at 1, another is seen in the 

 Glacier du Geant at g, Fig. 19, while a third forms the lower 



