ICE AND GLACIERS 223 



steep to allow fresh snow to rest upon them, and in which 

 the burden which presses the lower layers downwards is so 

 great that these can no longer retain their position on the 

 sides of the mountain. Thus, part of the snow which had 

 originally fallen on the higher regions of the mountain 

 above the snow-line, and had there been protected from 

 melting, is compelled to leave its original position and seek 

 a new one, which it of course finds only below the snow-line 

 on the lower slopes of the mountain, and especially in the 

 valleys, where, however, being exposed to the influence of 

 a warmer air, it ultimately melts and flows away as water. 

 The descent of masses of snow from their original positions 

 sometimes happens suddenly in avalanches, but it is usually 

 very gradual in the form of glaciers. 



Thus we must discriminate between two distinct parts of 

 the ice-fields; that is, first, the snow which originally fell- 

 called firn in Switzerland above the snow-line, covering the 

 slopes of the peaks as far as it can hang on to them, and 

 filling up the upper wide kettle-shaped ends of the valleys 

 forming widely extending fields of snow or firnmeere. 

 Secondly, the glaciers, called in the Tyrol firner, which as 

 prolongations of the snow-fields often extend to a distance 

 of from 4,000 to 5,000 feet below the snow-line, and in 

 which the loose snow of the snow-fields is again found 

 changed into transparent solid ice. Hence the name glacier, 

 which is derived from the Latin, glades; French, glace, 

 glacier. 



The outward appearance of glaciers is very characteristi- 

 cally described by comparing them, with Goethe, to currents 

 of ice. They generally stretch from the snow-fields along 

 the depth of the valleys, filling them throughout their entire 

 breadth, and often to a considerable height. They thus 

 follow all the curvatures, windings, contractions, and en- 

 largements of the valley. Two glaciers frequently meet 

 the valleys of which unite. The two glacial currents then 

 join in one common principal current, filling up the valley 

 common to them both. In some places these ice-currents 

 present a tolerably level and coherent surface, but they are 

 usually traversed by crevasses, and both over the surface 

 and through the crevasses countless small and large water- 



BC TO. XXX M 



