SNOW AND ICE. 
IOI 
forget my sensations, when standing with Tyndall on, 
as I supposed, the solid summit of the Galenstock, 
he struck his alpenstock into the snow, and I found 
that we were only supported on such a cornice pro- 
jecting over a deep abyss. 
When the snow falls at a temperature of o°-i2°, 
it assumes the form of stars or six-sided crystals. 
The region affected by glacial action may be 
divided into three parts: — 
1. The firn or Nevd. 
2. The glacier. 
3. The region of deposit. 
The Firn or Neve. 
The snow which falls in the higher Alpine regions, 
by degrees loses its crystalline form, becomes granular, 
and is known as Neve or Firn. It can be dis- 
tinguished at a glance from recent snow by being 
less brilliantly white, partly because it contains, less 
air, partly because the particles of meteoric and 
other dust give it a lightly yellowish, grey, or even 
brownish tinge. Sometimes it is in patches quite 
red. This is generally due to the presence of a 
minute alga (Sphierella nivalis). There are, however, 
several other minute organisms, plants, Infusoria and 
