New Orleans daily crescent. [volume] ([New Orleans, La.]) 1851-1866, 1860-05-28
Cooking By the sums Rays.

We're it not for the aerial envelop which sur
i rounds our earth, all parts of its surface wonlt
4 probably become as cold as night, by radiation
| into space. as the polar regions are during six
! months absence of the sun. The mode in which
the atmosphere retains the heat and increases the
temperature of the earth's surface, may be Illus
trated By an experiment originally made by saus-
sure. This physician lined j cubical wooden box
with blaekened cork, and after placing within it 4
thermometer, closely covered it with a top of two
panes Of glass, separated from each other BY thin
stratum of air. When this box was exposed to the
perpendicular rays of the sun, the thermometer in
dicated temperature within the box above that
OF boiling water. The same experiment was re-
peated at the Cape of Good Hope, by Sir John
herschel. with similar result, which was rendered
however. more impressive by employing the heat
thus accumulated in cooking the viands Of festive
dinner.
The explanation Of the result thus produced is
not difacult, when We understand that body
heated TO different degrees of intensity gives off
rays Of different quality. Thus, il an iron bali Be
suspended in free space, and heated to the tenn.
perature OF boiling water, it emits rays of dark
heat, OF little penetrating power, which are en-
trely Intercepted by glass. As the body is heated
To higher degree, the penetrating power Of the
rays increases, and finally when the Temperature
OF the ball reaches that Of glowing white heat,
y emts rays which speedily penetrate glass and
other transparent substances.
The heat which comes from the sun consists
principally Of rays Of high intensity and great pen
etrating power. They readily pass through glass.
are absorbed by the backened surface of the cork
and AZ This substance is q bad conductor of heat
iss temperature is soon elevated and it In turn "a
diates heat; but the rays which it gives off are of
alnerent character from those which it receives
lucy afe , hon'iaminous and have little penetrating
poWer tney cannot pass through the glass, and
are retained within the box and thus give rise Ia
the accumulation of the heat
me limit OF the increase of temperature will be
attained when the radiation from the cork ia of
such an intensity that it can pass through ina
glass, and the cooling from this source becomes
Just equal to the heating from the sun. The at
mnsphere which surrounds the earth produces 4
similar effect. II transmits the rays from the sun
and heats the earth beneath, which in its turn
emifs rays that do not readily penetrate the air.
but give rise to an accumulation Of heat ct the
surface.
The resistance OF the transmission Of heat of low
intensity depends upon the quantity of yapor CON
tanned 10 the atmosphere, and perhaps also on the
density OF the air. The radiation of the earth
therefore, differs very much on different nights and
In different localities In very dry places. as. for
example, In the African deserts and our own west
ern plains, the heat of the day il excessive, and
the night commensurate cool
y G0I0nel Emory states in his report on the Mexi-
can Boundary Survey, that in some cases. on the
arid plains, there was difference of COO between
the temperature OF the day and that or the night
indeed, the air Is SO permeable to heat even of
low intensities in this region that a very ren,arka
be difference was observed on some occasions
when the camp. ground was chosen in gorge be-
tween two steep hills. The Inter-radition between
tne nils prevented IN measure the usual diminu.
non 81 temperature, and the thermometer in such
suation stood several degrees higher than ON the
open plain. Lpros. J. Henry.
u