220 
THE FORMATION OF GLACIERS. 
the freezing-point, and thus producing constant 
alternations of freezing and thawing in the same 
mass of snow. This process amounts to a kind of 
kneading of the snow, and when combined with 
the cohesion among the particles more closely 
held together in one snow-flake, it produces gran- 
ular ice. Of course, the change takes place grad- 
ually, and is unequal in its progress at different 
depths in the same bed of recently fallen snow. 
It depends greatly on the amount of moisture 
infiltrating the mass, whether derived from the 
melting of its own surface, or from the accumu- 
lation of dew or the falling of rain or mist upon 
it. The amount of water retained within the 
mass will also be greatly affected by the bottom 
on which it rests and by the state of the atmos- 
phere. Under a certain temperature, the snow 
may only be glazed at the surface by the forma- 
tion of a thin, icy crust, an outer membrane, as 
it were, protecting the mass below from a deeper 
transformation into ice ; or it may be rapidly 
soaked throughout its whole bulk, the snow being 
thus changed into a kind of soft pulp, what we 
commonly call slosh, which, upon freezing, be- 
comes at once compact ice ; or, the water sinking 
rapidly, the lower layers only may be soaked, 
while the upper portion remains comparatively 
dry. But, under all these various circumstances, 
frost will transform the crystalline snow into more 
