Crawford avalanche. (Grayling, Mich.) 1879-19??, 1891-06-25

idea OF ice-making machinery, though
the matter is one susceptible of lucid
demonstration.
At a temperature OF 80 degrees Fab.
renheit water congeals and becomes ice.
To the schoolboy, yearning to try his
cherished skates, and the iceman eager
to begin the harvest Of his crop, this
process appears very slow one. II
would seem, indeed, that water, reduced
to a temperature below the freezing
point, ought almost instantly to take on
a crystalline form, and change en- masse
from a fluid to solid. For lack OF bet
ter terms we speak of nature as pos
sessed OF likes and dislikes; loving this
and abhorring that In this sense matter
seems both to change its state and take
on another and different condition
Were it not for this change would be the
rule; nothing would be stable; chaos
would reign. That water does not freeze
more rapidly Is due TO the presence in
it of latent heat, which must be expelled
before the change can take place.
Latent heat Is as mysterious an affair as
electricity. In no way can it affect the
senses; the most delicate thermometer
will not indicate its presence, yet IL is
none the less certain that IL exists and
in never varying quantities. To Illus
trate this, place block of ice at tenn
perature OF 80 degrees in kettle over
abpieit -fiEes-@VV Whom -ts4 entirely melted
the resulting water will be but little
raised In temperature from that OF the
ice. Faraday determined that to melt a
cubic yard Of Ice, about 1900 pounds,
without raising the temperature, re-
quires seventy pounds Of coal
It was known to the people of ancient
Rome that wet clothing becomes rapidly
and powerfully chilled. yet not one of
all her philosophers saw in the circum-
stance q suggestion for manufacturing
Ice to cool the wine and sherbet of roy
atty, in lieu of the snow brought from
the tops of mountains. This was left to
DR.. Joseph Black, the Scotch-1rish
chemist OF Edinburgh, who, about 1860,
who formulated and made public his ia
nous theory of latent heat. He found
that TO convert one pound of water at
212 degrees into steam, at the same tenn
perature, requires six and onehalf times
the heat necessary to raise the same
amount OF water from 81 to 2l2 degrees.
In other words, II one pound of steam at
gle degrees Is mixed with six and one
half pounds Of water at GO degrees,
there will result seven and one-half
pounds OF boiling water. IL was at
once evident that II, of six and one half
pounds Of water at SO degrees, one-half
pound could be suddenly converted into
steam, the remaining six pounds would
be frozen The problem was, how to
effect this
II any elastic fluid. atmospheric air,
for Instance, Is compressed, IL becomes
heated, and II cooled down to its orig
tnal temperature, the same heat must be
In, ha ~ ofA a..
Its normal condition. This heat is with
drawn from the atmosphere or other
surrounding substance, thus reducing
the temperature. BY the expansion OF
liquid sulphuric acid or solidifed car.
bonic acid, water can be frozen in red
hot dish, and small quantity added to
q glass Of boiling water will almost in
stantly convert 1t into solid ice. IL is
upon this principle of latent heat that
ice-making machinery depends.
The original or ground" patents for
lowering the temperature by machinery
expired some years ago. and are now
common property. In consequence of
this. vast numbers of ice.machinery
manufactures have sprung up all over
the civilized world, mora than fifty be-
ing located in the United States alone
Every mandatory has its own special
patents, and the number OF different
forms OF machines on the market is
hence very large They may, however.
all be reduced to two distinct varieties =
ether and ammonia machines
Ether machines include all those
where cold is produced by the evapora-
ton OF volatile liquid They include
the apparatus which employ sulphurIc
ether, gasoline, chymogene and other
dorgvativoa Of nntr0louu The lionfd il
evaporated in q partial vacuum, by
means OF which tho process is greatly
facilitated. Having absorbed heat in
the process the gas Is condensed and used
over and 0yer.
Ammonia machines differ from those
using ether .rrincipally IN this: that no