h air again,--just
as colorless glass may be crushed into white powder. On the other
hand, Professor Tyndall has converted slabs of snow to ice by regular
pressure, and has shown that every Alpine glacier begins as a snow-drift
at its summit, and ends in a transparent ice-cavern below. "The blue
blocks which span the sources of the Arveiron were once powdery snow
upon the slopes of the Col du Geant."

The varied and wonderful shapes assumed by snow and ice have been best
portrayed, perhaps, by Dr. Kane in his two works; but their resources of
color have been so explored by no one as by this same favored Professor
Tyndall, among his Alps. It appears that the tints which in temperate
regions are seen feebly and occasionally, in hollows or angles of fresh
drifts, become brilliant and constant above the line of perpetual snow,
and the higher the altitude the more lustrous the display. When a staff
was struck into the new-fallen drift, the hollow seemed instantly to
fill with a soft blue liquid, while the snow adhering to the staff took
a complementary color of pinkish yellow, and on moving it up and down
it was hard to resist the impression that a pink flame was rising and
sinking in the hole. The little natural furrows in the drifts appeared
faintly blue, the ridges were gray, while the parts most exposed to
view seemed least illuminated, and as if a light brown dust had been
sprinkled over them. The fresher the snow, the more marked the colors,
and it made no difference whether the sky were cloudless or foggy. Thus
was every white peak decked upon its brow with this tiara of ineffable
beauty.

The impression is very general that the average quantity of snow has
greatly diminished in America; but it must be remembered that very
severe storms occur only at considerable intervals, and the Puritans did
not always, as boys fancy, step out of the upper windows upon the snow.
In 1717, the ground was covered from ten to twenty feet, indeed; but
during January, 1861, the snow was six feet on a level in many parts of
Maine and New Hampshire, and was probably drifted three times that depth
in particular spots. The greatest storm recorded in England, I believe,
is that of 1814, in which for forty-eight hours the snow fell so
furiously that drifts of sixteen, twenty, and even twenty-four feet were
recorded in various places. An inch an hour is thought to be the average
rate of deposit, though four inches are said to have fallen durin