The Mount Holly news. [volume] (Mount Holly, Burlington Co., N.J.) 1891-1942, 1908-04-28
i SYoIEd IN USE FOR AGES.

Shallow Porous Earthen Dishes In
Which Water, by the Process OF
Rapid Evaporation and Heat lnsuia
tion, Is Congesied During the Night.
In hot India. where every day in the
year the resident gets all the heat he
wants. there are four or five months
of the year-November to March
when the nights although never reach
ing even to freshness, can be made to
produce many tons of ice in the open.
The fields in which the ice is made
are low, fat and open, and the ice is
produced in large lots when the tenn
perature of the air is 10 degrees or
20 degrees F. above the congeallng
point writes L. Lodian In the Scientific
American. The method practiced is an
instructive example Of keen observa-
ton adapted to material purposes by a
nation which is today ignorant of the
science of the thing-that is, they could
not explain if questioned what actually
causes the forming of the ice beyond
a few vague phrases, like ''the wind
and keeping the earthly heat down"
Yet this same ice forming process has
been utilized in India since the ages
that are '1ost in the night of time" and
all with a scientific observation and ac-
curacy which the Hindoo has acquired
by instinct handed down through count
less generations.
The ice plot is a rectangular piece
of ground. say. 100 feet long by 80
broad, running in an easterly and west
erly direction. The soil is removed to
a depth of a couple of feet This ex-
cavation when made is smoothed and
then allowed to remain exposed to the
torrid rays of the sun to dry; then rice
straw in small sheaves is laid In an
obliuue direction in the hollow, with
loose straw on the top to the depth OF
a foot and a half, leaving its surface
half a foot below that of the ground.
Numerous beds of this kind are form
ed-the ensemble constituting the Ice
farms-with narrow sidewalks between
them. in which here and there large
covered earthen water jars are sunk
in the ground for the convenience OF
having water near by to I'LL the shallow
earthen vessels in which it is to be
frozen. These dishes are nine inches
in diameter at the top, diminishing to
Eve inches at the bottom, one and one
half inches deep and one-quarter inch
thick, and are SO porous as to soon be-
come moist throughout when water is
placed in them
When evening comes the shallow
earthenware pans are placed in rows
upon the litter, and by means of little
burned tilt pots secured to the ends of
lengthy bambusa canes each pan is
half filed with water. The quantity
nevertheless varies according to the
expectation of ice The natives can
forecast that by the aspect of the heav
ems and the evenness with which the
air currents come from the northwest.
There are about 5000 plates in each
of the beds, and the ice yield will av-
erage quarter pound. from each dish.
In the cool season when the tempera
ture of the air at the ice fields is I'M
der so degrees F. and there are gentle
breezes from the north and west direc-
lions ice appears in a night in all of the
shallow pans. Native watchers are on
the lookout to note when thin film
appears on the water in the pans, when
the contents Of several are mixed to-
gether and sprinkled over the other
dishes. This method augmentS the
freezing action.
Stagnation has been discovered by
the natives to diminish the quantity Of
tor tho firm q mont ic
entirely clear. with zephyr currents
from the northwest, the congelation
begins before or about midnight and
continues to advance till morning.
when the thickest ice is formed. 1t is
often an inch thick, and sometimes the
whole contents of the dish are frozen
compact
The ice dishes present large moist
external surface to the air currents,
producing rapid evaporation and a
lowering of the temperature. The wa
ter which percolates through the po-
rous trays exposes so large a surface
to the breeze that it is promptly fro
zen In addition to the evaporative
effect we also have the influence of
heat insulation to fall back upon in
explaining the phenomenon.
The thick layer of dry straw in the
ice beds forms large surface which
is a poor conductor of heat. The heat
can penetrate but a little way into it
during the day. So soon as the sun
sets sets this large and powerfully ra-
dating surface is brought into action
and affects the water in the thin. po
rous pans, themselves strong radiators.
Some of the natural ''ice farms" of
Bengal produce in a single night over
ten tons of ice. employing 800 persons
of all sizes and ages. and the early
morning harvesting of the ice by these
1.-THE gentry darting about is one of the
few animated scenes worth noting in
the Gauges region.