244 ON GLACIERS IN GENERAL. 



occurs at a somewhat lower level. It cannot be too distinctly 

 understood that the fresh snow annually disappears from the 

 glacier proper. Where it ceases entirely to melt, it of course 

 becomes incorporated with the glacier. We hav'e therefore 

 arrived at the region where the glacier forms; everywhere 

 below it only wastes. This snowy region of the glacier is 

 called in French neve ; in German, firn. As we ascend the 

 glacier it passes gradually from the state of ice to the state of 

 snow. The superficial layers become more snowy and white, in 

 fact, nearly pure snow ; the deeper ones have more colour and 

 consistence, and break on the large scale into vast fragments, 

 which at Chamouni are called seracs. The neve moves as the 

 glacier proper does, and it is fissured by the inequalities of the 

 ground over which it passes. These fissures are less regular 

 than those of the lower glacier. They are often much wider, 

 in fact, of stupendous dimensions, and being often covered with 

 treacherous snowy roofs, constitute one of the chief dangers of 

 glacier travelling. The constitution of the neve" may be well 

 studied on the Glacier du Geant, a tributary of the Mer de 

 Glace. 



The mountain-clefts in which large glaciers lie, usually 

 expand in their higher portions (in conformity with the ordinary 

 structure of valleys) into extensive basins in which snow is per- 

 petual, and which therefore contain the nev6, the true origin and 

 material of the glacier, which is literally the overflow of these 

 snowy reservoirs. The amount of overflow, or the discharge of 

 the glacier upon which depends the extent of its prolongation 

 into the lower valleys depends in its turn on the extent of the 

 neve or. collecting reservoir. Glaciers with small reservoirs, of 

 necessity perish soon. Their thickness is small, and consequently 

 the wedge of the glacier soon thins out. Such glaciers are com- 

 mon in confined clefts of the higher mountains. Being destitute 

 of reservoirs, they soon terminate abruptly. Such are the gla- 

 ciers of the second order described by De Saussure. They are 

 exceedingly numerous in all glacier-bearing chains of mountains, 

 but from their comparative smallness and inaccessibility, they 



