44 THE BOOK OF NATURE STUDY 



more like ice. We suspect, [then, that it is the air in snow that 

 makes it white, and that if all the air could be squeezed out it would 

 be transparent like ice. What is snow, then, if not needles of ice 

 with a great deal of air between the particles ? 



Having reached this point, we should show some pictures of 

 Alpine scenery. The familiar view of the Matterhorn is an excel- 

 lent one for the purpose. This is a very high hill, so high that 

 on the top of it the snow never completely melts. But high and 

 cold as it is we notice that a good deal of it is bare rock, with no 

 trace of snow. Why is this ? When we look closer we find that 

 the bare parts are the steep parts, and we suspect that they are 

 bare, not because snow does not fall there, but because as soon 

 as it reaches a certain thickness it has no longer the power of 

 clinging to the steep slope, but begins to glide downwards, moving 

 faster and faster as it goes, like the snow on a steep roof. When 

 we look again at the picture, and see how the snow is piled up in the 

 places where the slope is gentle, we see that this must be so. But 

 those hollows and gentle slopes must then receive not only their 

 own snowfall, but also all the accumulations of snow that have slid 

 off the steep upper slopes. If, at the bottom of a snow drift eight 

 or ten feet deep, the snow turns into something resembling ice, 

 what must it be when there are hundreds of feet of snow on top 

 of it ? It becomes pure solid ice. But this ice and snow never 

 melt ; they remain there year after year, summer and winter. 



We think of our summer excursions to a hill, and we remember 

 how we saw that the mountain robs the air of the moisture that 

 that air stole from the sea or the river, and that the use of the 

 mountain is to give back this moisture to sea and river. But 

 the snow and ice are just frozen water is this mountain an excep- 

 tion, does it never give back to the rivers the water which the air 

 took from them ? Some of the snow and ice melts, no doubt, in the 

 hot sun of summer, and so flows downward, but much of it does 

 not melt at all up on the cold mountain-side. What happens then ? 

 As the snow is more and more pressed into ice, and as the heaps of 

 ice and snow get thicker and thicker, the ice begins to creep slowly 

 downward towards the valley, as a slow-moving river of ice. As 

 it creeps down and down it loses the cold breath of the mountain, 

 more and more it feels the warm air of the valley. As it moves, 



