INTRODUCTORY. 



comparatively motionless part corresponding to the lake 

 out of which a river often flows. Technically this is 

 called the neve. 



Glacial ice is formed from snow where the annual fall 

 is in excess of the melting power of the sun at that point. 

 Through the influence of pressure, such as a boy applies 

 to a snow-ball (but which in the neve field arises from the 

 weight of the accumulating mass), the lower strata of the 

 neve are gradually transformed into ice. This process, is 

 also assisted by the moisture which percolates through the 

 snowy mass, and which is furnished both by the melting 

 of the surface snow and by occasional rains. 



The division between the neve and the glacier proper is 

 not always easily determined. The beginnings of the glacial 

 movement — that is, of the movement of the ice-stream 

 flowing out of the neve field — are somewhat like the begin- 

 nings of the movement of the water from a great lake 

 into its outlet. The neve is the reservoir from which the 

 glacier gets both its supply of ice and the impulse which 

 gives it its first movement. There can not be a glacier 

 without a neve field, as there can not be a river without a 

 drainage basin. But there may 

 be a neve field without a glacier — 

 that is, a basin may be partially 

 filled with snow which never melts 

 completely away, while the equi- 

 librium of forces is such that the 

 ice barely reaches to the outlet 

 from which the tongue-like pro- 

 jection (to which the name glacier 

 would be applied) fails to emerge 

 only because of the lack of mate- 

 rial. 



A glacier is characterised by both veins and fissures. 

 The veins give it a banded or stratified appearance, blue 

 alternating with lighter-coloured portions of ice. As these 



Pig. 2.— Illustrates the forma- 

 tion of veined structure by 

 pressure at the junction o"f 

 two branches. 



