THE FORMATION OF GLACIERS. 219 
ena for ourselves, if we have any curiosity to do 
so. The first warm day after a thick fall of light, 
dry snow, such as occurs in the coldest of our 
winter weather, is sufficient to melt its surface. 
As this snow is porous, the water readily pene- 
trates it, having also a tendency to sink by its 
own weight, so that the whole mass becomes 
more or less filled with moisture in the course of 
the day. During the lower temperature of the 
night, however, the water is frozen again, and the 
snow is now filled with new ice-particles. Let 
this process be continued long enough, and the 
mass of snow is changed to a kind of ice-gravel, 
or, if the grains adhere together, to something 
like what we call pudding-stone, allowing, of 
course, for the difference of material ; the snow, 
which has been rendered cohesive by the process 
of partial melting and regelation, holding the ice- 
globules together, just as the loose materials of 
the pudding-stone are held together by the cem- 
ent which unites them. 
Within this mass, air is intercepted and held 
inclosed between the particles of ice. The pro- 
cess by which snow-flakes or snow-crystals are 
transformed into grains of ice, more or less com- 
pact, is easily understood. It is the result of a 
partial thawing, under a temperature maintained 
very nearly at thirty-two degrees, falling some- 
times a little below, and then rising a little above 
