38 THE CANADIAN NATURALIST. [Feb. 



innumerable transverse cracks or crevasses, penetrating apparently 

 to the bottom of the glacier, and with slippery sloping edges of 

 moist ice threatening at every step to plunge the traveller into the 

 depths below. Still the treacherous surface is daily crossed by 

 parties of travellers apparently without any accident. The whole 

 of the ice is moving steadily along the slope on which it rests, at 

 the rate of eight to ten miles daily ; the rate of motion is less in 

 winter and greater in summer ; and farther down, where the glacier 

 goes by the name of the Glacier du Bois, and descends a steeper 

 slope, its rapidity is greater ; and at the same time by the opening 

 of immense crevasses its surface projects in fantastic ridges and 

 pinnacles. The movements and changes in the ice of these 

 glaciers are in truth very remarkable, and show a mobility and 

 plasticity which at first sight we shoald not have been prepared to 

 expect in a solid like ice. The crevasses become open or closed, 

 curved upwards or downwards, perpendicular or inclined, accord- 

 ing to the surface upon which the glacier is moving, and the whole 

 mass is crushed upward or flattens out, its particles evidently 

 moving on each other with much the same result as would take 

 place in a mass of thick mud similarly moving. On the surface 

 of the ice there are a few boulders and many stones, and in places 

 these accumulate in long irregular bands indicating the lines of 

 junction of the minor ice streams coming in from above to join 

 the main glacier. At the sides are two great mounds of rubbish, 

 much higher than the present surface of the glacier. They are 

 called the lateral moraines, and consist of boulders, stones, gravel 

 and sand, confusely intermingled, and for the most part retaining 

 their sharp angles. This mass of rubbish is moved downward by 

 the glacier, and w\th the stones constituting the central moraine, 

 is discharged at the lower end, accumulating there in the mass of 

 detritus known as the terminal moraine. 



Glaciers have been termed rivers of ice ; but there is one 

 respect in which they differ remarkably from rivers. They are 

 broad above and narrow below, or rather their width above cor- 

 responds to the drainage area of a river. This is well seen in a 

 map of the Mer de Glace. From its termination in the Glacier 

 du Bois to the top of the Mer de Glace proper, a distance of about 

 three and a half miles, its breadth does not exceed half a mile, 

 but above this point it spreads out into three great glaciers, the 

 Geant, the du Chaud and the Talefre, the aggregate width of 

 which is six or seven miles. The snow and ice of a large interior 



