The Olneyville times. (Olneyville [Providence, R.I.]) 1887-1917, 1908-09-25
Structure Of HailStOneS.
by CLEVELAND ABBE.

There are three plausible hypothe-
ses as to the origin OF the snowy ice
at the centre Of a hailstone.
(a) The hailstone may have be-
gun with the formation of a ball OF
snow, and the clear ice may be a
deposit OF cold water, frozen few
seconds later by the cold OF the
surrounding atmosphere. In this
case the air that is mixed with the
snowy ice at the centre would be
compressed by the freezing OF the
surrounding clear ice. and would be
liberated as bubble when the hail
stone is melted under water.
OBJ The nucleus of the hailstone
may have been at first a large drop
OF water, containing dissolved air,
which is forced out by the process OF
freezing. precisely like the bubbles
OF air that are seen in cakes of arti-
fetal fee. Cold water can dissolve
an appreciable percentage OF its VOL
ume of air, all of which is eItruded
when water freezes; bubbl. OF
highly compressed air might thus be
formed at the centre OF the hailstone.
II such a hailstone be melted in cold
water slowly. all OF this air will be
redissolved, and no bubble will be
seen to rise to the surface. II the
stone be dissolved in hot water rapid
ly, or especially if the stone be
crushed forcibly and quickly under
water, the air may escape as a bub-
BILE without having had time to be
redissolved.
(c) A hailstone formed of pure
water that has had no opportunity
to absorb or dissolve air can be re-
duced to a temperature far below
freezing, but will eventually turn to
ice, at which moment its tempera-
ture will rise to thirty-two degrees
Fahrenheit, and it will assume a
| crystalline structure, so as to re-
semble snow. Such hailstone has.
| therefore, snowy nucleus without
inclosed air, and on being melted
under water will, of course, show no
bubble. In fact, the central space
is occupied, not by air, but by the
vapor of water only, and as the
pressure is very small, we may liken
/ this to a partial vacuum.
All these three forms of hailstones,
and other forms as yet unthought
/ Of, are possible; and if we could in
/ vent methods OF distinguishing be.
tween these three kinds Of hailstones
we should have a better knowledge
/ of what goes on In the upper all
! during the formation of hail.
Those VINO have proper convent.
! ences will find that the study of hail.
: stones under polarized light gives
additional information as TO theiI
q CRY ystalline structure, but has not az
| yet told Us much about the process
| OF formation.
As ice is poor conductor of heat
/ it is worth while 10 make some effort
TO determine the temperature OF the
! interior OF large hailstone. Ths
| external surface may safely be as.
! sumed to have the temperature Of
! evaporation or the average wet
! bulb temperature prevailing in the
! lower thousand feet of air through
which the hail has rapidly fallen.
but the centre must be at a tempera-
ture more nearly corresponding TO
that at which the nucleus was
formed. There is, therefore, a state
Of strain that should be revealed by
polarized light. The average tenn
perature of the whole hailstone may
be easily and directly determined by
allowing hail 10 melt within a
calorimeter, where the heat con-
sumed can be determined, and then
the temperature be computed
Monthly Review.