1908] 0)1 Ice and its Natural History. 265 



are united and held together by ligaments, the grains of the glacier 

 are united by an aqueous cement, which has a slightly lower melting 

 temperature than tneir own. 



vVhenwewaik on the glacier we crush under foot nothing but the 

 grains of the glacier, whicli have been loosened for our beneht by the 

 radiant energy of the sun. If the white surface layer of the disinte- 

 grated ice be chipped away with an ice-axe, so as to expose a smooth 

 surface of blue ice, in the course of a single summer's day, this smooth 

 blue surface will become as white and crumbling as any other part of 

 the surface of the glacier. If it were not for this interaction between 

 the solar rays and the granular ice, traversing a glacier in summer 

 would be almost an impossibility. 



" iSnow Neve and (jlacier. — In the lowlands, snow falls and melts 

 again, and we have no opportunity of witnessing the metamorphoses 

 which it may experience when lying for a long time on the ground. 

 It is otherwise with the snow which falls in the high mouncains. 

 There the temperature of the air is nearly always below the melting- 

 point, and the snow may remain for years without reaching that tem- 

 perature. It is often assumed that tne iiigher we climb amongst the 

 mountains, the greater is the quantity of snow which falls in the year. 

 But this is a mistake. In the Alps tne greatest amount of snow falls 

 at a height of from 2U00 to '^^b'^^ metres a Dove the sea. The crystalline 

 snow ot the mountains takes the granular form much more easily than 

 does the haky snow of the lowlands. The snow that falls on glaciers 

 m the winter melts and disappears during summer like that on the 

 neighbouring lands. Snow in the higher regions which has persisted 

 through a summer passes into tirn or neve. This is always in clearly 

 granular form. 



It is to Hugi that we owe most of our exact knowledge and 

 detailed description of the neve or tirn, of its genesis and of its 

 metamorphoses. He built a hut on the I'insteraarlirn at an eleva- 

 tion of ooUU metres, and inhabited it for a considerable time for the 

 sole purpose of studying the hrn or neve and its natural history. 

 He traces the development of the neve from the line crystalline snow 

 of the highest levels, and observes it as it passes into glacier. At a 

 heigiit ot oUOO metres the transformation has taken place at a depth 

 of 7 metres below the surface of the neve ; at an elevation of liVUO 

 metres it is met with at a depth of a few feet, and at a height of 

 2400 metres the neve has passed into glacier at the surface. In 

 experimenting on the neve, he found that when a hard compact mass 

 of It was exposed to the inhuence of rising temperature, the binding 

 material ot the grains soon dissolved to water without the grains 

 themselves being apparently attacked at all. A lower temperature 

 then reunites the grains so tiiat the whole appears as a uniform 

 compact mass. This shows the lower melting-point of the less pure 

 cementing mass of ice. He sums up the whole history of the 

 development of the glacier in a remarkable passage (p. 7o) of his work 



