21 



its bed. aud conveys stones, and sand, and mud. Many of the 

 glaciers in S%vitzerland are covered with impurities, gathered from 

 neighbouring rocks ; those in Norway are less covered with clebris, 

 and their ice is clear. A glacier moves slowly down its inclined 

 bed. As in the case of the river, its centre moves more rapidly 

 than its sides, and the top more rapidly than the bottom. This 

 movement is readily demonstrated by means of stakes driven at 

 equal distances across the glacier in a straight line. Those in the 

 middle of the glacier are found to advance the most rapidly. 



The ice of a glacier, being formed of compressed snow, like a 

 snowball, is not hard like the frozen water of pond ice. Indepen- 

 dently of cracks and crevices in the ice itself, the glacier presents 

 many irregiilarities of surface owing to the presence of stones, which 

 have fallen from the rocks in the gorges through which it has 

 passed. These stones are accumulated in lines which traverse the 

 length of the glacier, and which are called •■ moraines." As the 

 glacier moves downwards, the stones are carried with it, and are 

 finally deposited in a large heap at the foot of the glacier, in 

 what is known as a " termiiuxl moraine." 



Sometimes a stream of water forms on the siirface and runs 

 down the ice-way. If it comes to a crack in the glacier it dis- 

 appears down the crack ; and gradually mdening the opening, forms 

 a cascade which plunges with a tremendous roar into the very heart 

 of the glacier. This is known as a " monlin." or •• glacier-mill.'" 



The sides of a glacier are usually very irregularly cracked and 

 broken. The marginal " crevasses " are due to the fact that the ice 

 at the side, immediately adjacent to the rock, does not move so 

 rapidly as that a short distance away from it, and hence the ice 

 becomes rent or creviced. This system of crevasses becomes ex- 

 tremely complex as the ice passes onward, but it is usually obliterated 

 when the glacier passes through a narrower part. There is generally 

 at the teiminus of a glacier, a cave or grotto of ice, caused by 

 streams of water mnning through it. This occasionally tonus a 

 continuous cavern of considerable length, extending far into the 

 glacier. 



Glaciers move with vaiying I'apidity, faster, however, in summer 



