SNOW SQUEEZED TO ICE 31 



are burst by frost. And similarly it is owing to this 

 swelling of water when freezing that the wet soil and 

 surface rocks are, when frozen in winter, broken and 

 rendered permeable to later rains. But even more striking 

 is the result of this bursting action of freezing water upon 

 the great rocky sides of mountains. The water, formed 

 by melting snow and by rain, lodges in cracks and fissures 

 of the rocks, and, when the cold of winte? comes on, it 

 freezes and consequently swells in volume, and so shatters 

 the imprisoning stone. Thus it breaks off huge masses 

 and helps to wear away the mountain peaks and sides. It 

 is owing to the expansion of water on becoming solid that 

 a given bulk of ice is lighter than the same bulk of water, 

 and that therefore ice floats on water, and our streams 

 and lakes do not freeze solid from bottom to top. 



Important and exceptional as are these properties of 

 water — producing great results, which we can observe in 

 the frozen world of the Alps — they do not help us to the 

 understanding of a glacier, nor would they suggest to us 

 as a natural process the production of glaciers by the 

 change of great heaped-up masses of snow on mountain 

 sides. The one familiar property of snow, or powdered 

 ice, which has to do with the conversion of mountain snow 

 into the huge rivers of solid ice called " glaciers," is the 

 curious " binding " quality which enables us to make 

 "snowballs" by squeezing handfuls of snow. Every 

 schoolboy knows that if one takes up a double handful 

 of snow during a hard frost and lightly presses it, it 

 remains a loose powder. But if one squeezes the snow 

 very firmly and persistently (or with less squeezing if a 

 slight thaw has set in), the particles adhere to one another, 

 and the snow becomes hard and more or less compact ice. 

 Boys consider it an unfair and brutal thing to squeeze a 

 snowball so much as to make it thoroughly solid, since 

 it then becomes as dangerous a missile as a big stone. 



