Evening star., 1936-02-16
Bv CaIvin Fraser.
T IS a common mistake to think
of ice as a comparatively simple

-. of ice as comparatively simple
- substance-always pretty much
.- a a..ke-the facts about which can
be told in a few words. They cannotI
Enough has been written about ice to
AL a great library.
We often speak of ''ice and snow"
as if we were referring to two diff
ferent products of nature. What we
usually mean is "ice, including SNOW"
for the latter is merely ice in par
ticular form, or, rather, an immense
variety of forms. Ice is a mineral,
and it is one of the most remarkable
to be found on the earth, partly be-
cause of the extremely varied shapes
1t assumes and partly because of its
curious properties.
Every severe cold wave brings evi-
dence, in the shape of ruptured water
pipes, Of the fact that water expands
in freezing. Nearly all substances in
crease in density and shrink in vol
une when they cool, and SO does water
down to certain point on the tenn
perature scale. It reaches its greatest
density at a temperature of 1872
Fahrenheit. Further cooling causes
very gradual expansion until the tenn
perature reaches the freezing point
80 Fahrenheit-When, as the water
changes to ice, there is a sudden ex-
pansion, amounting to about one
eleventh of the volume Of the water.
~, This is due to the formation in the
substance at that stage of innumerable
tiny crystals.
- A block Of clear, hard ice does not
reveal to casual inspection the slight
est hint of its complex structure.
There are. however, several ways of
bringing 70 view the innumerable
starry crystals of which it is composed.
One method is to rub the surface with
a soft pencil or to dust it lightly with
SCOT by means of soft brush. The
substance thus applied fills the slight
depressions between neighboring crys-
tails and discloses their outline. A
coating of SCOT can be used in a SIM
liar way to bring out the details Of
the frost figures formed on window
panes.
Another process consists in pass
ing a beam of light through a thin
slab of ice and watching the result
ing image projected on a screen. Lit
tie shining figures appear in the shape
of six-petaled flowers. Each of these
represents an open space in the ice
where a crystal has been melted by
the heat of the beam and retains the
shape of the crystal. The space is
nearly filled with water, but, as ice
contracts in melting, a tiny bubble
like vacuum is left at the center of
each flower. The spaces and their
contents have sometimes been called
negatives" or inverse" crystals.
ICE crystals include those formed
in the free air, as cloud and snow
crystals; those deposited on the sur
face Of terrestrial objects, as hoar-
frost, rime, etc, and those formed in
bodies of water. The ice crystal Is
one of natures outstanding mysteries.
All capitalization is mysterious. but
the case of ice is the most remarkable
because its crystals occur in a far
greater variety of forms than do those
OF any other substance.
The microscopic study Of ice crys-
tails, especially as seen in snoWfakes,
began almost as soon as the micro
scope was invented, but the wealth
of information We now possess con-
cerning these fascinating objects has
been obtained mainly since the be-
ginning of the. present century, with
the aid of microphotography. One
man-the late Wilson A. Bentley
probably photographed greater num-
ber of different forms than have been
pictured by the combined work Of all
other photographers. He left col
lection of more than 5000 negatives,
about half of which are represented
in the marvellous album entitled Snow
Crystals" published a few weeks be-
fore his death.
Bentley, though he enriched science
through his labors, was neither SCI
entific man nor a scholar. He was
Vermont farmer, who for 46 years
pursued the photography of ice crys-
tails as a hobby His beautiful pictures
began appearing In books and maya
zines many years ago and he became
known to fame as the snowflake man" }"
He once told me that including the
value of his time, estimated at the
low rate of $3.50 a day, he had in
vested upward of $4,000 in his photo
graphs, while the gross proceeds from
their sale did not exceed $4,000. His
pictures have furnished many deco
rative designs for fabrics, wall paper,
Christmas seals and the like.
Snow crystals of the simpler forms,
mainly in the shape of hexagonal
plates and columns, float in the lofty
feathery clouds and in very cold
weather sift down as fine snow or
fill the lower air with sparkling
haze of diamond dust" as it is
called by polar explorers. Crystals of
more elaborate shapes, many of which,
under the microscope, show much
branching and rebranching as well as
a diversity of markings in the shape
Of grooves, ridges and cavities, occur
in the feecy Winter clouds of lower
level. Most snowflakes are clusters of
these crystals, more or less broken
through contact with one another.
The largest fakes fall in relatively
mild Winter weather. Some accur-
ately measured snowfiakes have been
found to be inches In diameter, and
there are dubious tales Of much larger
fakes.
RESIDES snow, three different kinds
Of Icy particles fall from the sky.
All three are commonly called "hai"
by the man in the street, but SCI
ence has separate names for them.
True hail, containing concentric lay
ers of clear and SNOWY ice falls dur.