ICE AND GLACIERS. Ill 



that few mountains of the earth can be compared with 

 them in this respect. Such a development of the glacial 

 world is, as far as we know, met with only on the Hima- 

 layas, favoured by the greater height ; in Greenland and 

 in Northern Norway, owing to the colder climate ; in a 

 few islands in Iceland ; and in New Zealand, from the 

 more abundant moisture. 



Places above the snow-line are thus characterised by 

 the fact that the snow which in the course of the year 

 falls on its surface, does not quite melt away in summer, 

 but remains to some extent. This snow, which one 

 summer has left, is protected from the further action 

 of the sun's heat by the fresh quantities that fall upon 

 it during the next autumn, winter, and spring. Of this 

 new snow also next summer leaves some remains, and 

 thus year by year fresh layers of snow are accumulated one 

 above the other. In those places where such an accu- 

 mulation of snow ends in a steep precipice, and its inner 

 structure is thereby exposed, the regularly stratified yearly 

 layers are easily recognised. 



But it is clear that this accumulation of layer upon 

 layer cannot go on indefinitely, for otherwise the height 

 of the snow peak would continually increase year by year. 

 But the more the snow is accumulated the steeper are the 

 slopes, and the greater the weight which presses upon the 

 lower and older layers and tries to displace them. Ulti- 

 mately a state must be reached in which the snow slopes 

 are too steep to allow fresh snow to rest upon them, and 

 in which the burden which presses the lower layers down- 

 wards 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 

 dtion and seek a new one, which it of course finds only 



