The Point Pleasant register. [volume] (Point Pleasant, W. Va.) 1909-1939, 1910-02-02
PROPERTIES OF ICE.
Gfax Skating Is Easier When the Ten.
Rerature Is Not Too Low.


Rerature Is Not Too Low.
Why can we skate more easily
whom the weather is not too cold?
Why do our skates EFbite" or take
hold of the ice better when the tenn
perature is not far below the freez-
lg point? The explanation of this
ample and universally recognized
Sact Will enable US also to see the
EeGson for another, the truth of
Hlneh Is recognized by every school
og-namely, that snow will pack
ESTER into snowballs when nearly
ats melting point.
The explanation Of both these
facts lies in an Utmost unique prop
I ertE Of water or, rather, ice, which
eauscs It to melt or tend to melt
when pressure is applied to it. When
the pressure is relieved, if it is still
Below its normal freezing tempera-
at once solidifes again.
S property is beautifully Illus
In a familiar experiment in
large cake of ice is used,
Jed at each end. If a loop Of
ire is passed around it and
hit attached to the end it will
gDe noted that the wire is slow
Cutting its way through the ice,
t curiously enough without eaus-
any division OF the cake, for the
is melted into water by the
sssure directly beneath the wire,
Ich water at once freezes into ice
in above the wire, so that per-
laps after an hours time the wire
Sill have cut its way completely
through the cake, leaving it, how
sver, as solid and whole as ever.
In the case Of the skater, then,
she weight of his body carried on a
arrow skate may produce a pres
re on the ice sufficiently great to
cit a small groove under the edge
the runner. This enables it to
ke hold Of the ice more readily,
81, Furthermore, the water acts as
lubrieant on the ice and makes it
pperE l. Since considerable pres
ne is necessary to produce melting
zen when the temperature is only
degree or so below the normal
it1ng point, this effect Will not
ede place on a very cold day, for,
Is well known, very cold ice is not
ppery. The same explanation
5lds for snowballs. But the pres
IRE developed in this case is much
sss so that melting enough to
pack" well will not occur unless
e snow is nearly warm enough to
,elt anyway.
This effect is noted on a grand
scale in the case Of glaciers, which
aow slowly down 4 mountain side
much as If ice was q vicious fluid.
The great pressure developed along
the bottom as well as at the turns
and other points causes a slight
melting, which IS Immediately fol-
lowed by freezing again as soon as
he pressure is relieved. This en-
hles the lee to adapt itself to the
nape OF the valley as it proceeds on
S way.
Ice is one of the few substances
at show tins effect of melting IN
pressure, and it does so because
the fact that water expands on
,stezing. The great majority of
Tubstanees contract on solidifying
nd hence would show the reverse
Tect-that Is, pressure applied TO
ZEN in the mclten state would tend
cause soidifcation.
This is one reason for believing
lat the interior Of our earth as a
cole is solid rather than molten,
br, while we believe that the tenn
erature OF the interior NAV be
much more than enough to melt
rock under ordinary conditions
and indeed volcanoes show that
there is plenty Of molten rock not
SO very far below the surface-the
enormous presSures that exist deep
down in the earth are enough to
Keep the material in solid condi-
tlon.-Minneapois Journal.
The Gar.