Richmond enquirer. [volume] (Richmond, Va.) 1815-1867, 1833-04-19
From Lardncr's Treatise ON Heat.


REGARDED-The common spectator who on clear night
behos the ornament thinks he obtains Just the
position aud arrangement ohe brilliant objects with which
IL Is so richly furnished. The vision of the
ronomer discovers, however that he behods this story
vault through disorting medium; that in fact he views
II through great lens of air by which every object is
moved from its proper place. nay more, that this distortion
varies from night TO night, and from hour TO hourvaries
with the varying heat OF the atmosphere which produces
It, Such distortion, and the variations TO which il is sub
ec must then be accurately ascerained before any in
terence can be made respecting the motion, positions
mude or distance OF any object the heavens aud
ceTtalned II cannot be- unless the laws which
phenomena OF heat be known. But the very instruments
which the same astronomer assist vision and TO
note and measure the positions and mutual distances the
objects oil his inquiry, themselves emnenty subject
! to the same dsortng influence The metal OF which
they are formed swes and with every luctua-
ton IN the heat TO which it is exposed. sunbeam,
blast oil cold air. nay the very heat of the astronomers
own body, must produce effects the figure of the braZen
ach by whose divided surface his measurements and his
observations are elected Such effects therefore
known, and taken into account he hope TO attain
that accuracy, which the decacy of his Investigations
renders ndispensably necessary.
INGENIOUS APPLICATION OF THE PRINc1pIE
THAT SOLID BODIES ARE DILATED OR CoNTRAcr-
ED BY CHANGES OF INTERNATIONALLY principle
was beautifully applied by NJ. Moard some years ago in
Paris The weight OF the roof of the large gallery OF the
Conservative DIES dTtS ct Meters pressed the sides out
wards so as TO endanger the building and it requisite
TO Ind means by which the wall should be propped
to sustain the roof Nj. Molard contrived the following
ingenious plan for the purpose: series OF strong iron
bars were carried across the building from wall to H.
passing through holes in the walls aud were secured by
nuts the outside. In this state they would have been
sufficient to have prevented the further separation of the
walls by the weight OF the roof but il desirable to
restore the walls TO their original by drawing them
together. This effected in the following manner-
alternate bars were heated by lamps fixed beneath them
They expanded; and consequently the nuts which were
previously in contact with the walls, no longer So
These nuts were then screwed up TO be again in
close contact with the walls The lamps were Withdrawn
and the bars allowed TO COOL In cooling they gra-
dualy contracted, and resumed their former Dimensions
consequently the nuts, pressing against the walls, drew
| he Dpptb fhron a.
which they had been screwed up. Meanwhile the inter
mediate bars were heated and expanded and the nuts
screwed up before. The lamps being ain Withdrawn
they contracted in cooling, and the walls further
drawn together This process continually repeated
until at length the walls restored to their perpe nd
bars extending f. ana binding together its walls "e
EFFECTS OF EvAPoRATIoN.-The depression of tenn
peraure produced by evaporation will be percept-
BILE the rapid is the evaporation because then the
body from which the heat is distracted has not time 10
receive supply OF heat from the surrounding objects
replace that which it has drawn Hence by conduct
ing the process of evaporation in vacuum, where the
evaporation is almost instantaneous the cooling
more conspicuous IL quantity OF included in the
bulb OF thermometer tube be surrounded with sponge
mosened with ether and placed under the of an
air-pump, the moment the air is withdrawn the ether
evapOates; and ii sufficient quantity ether be applied
the water in the bulb will be frozen.
| The same fact may he exhibited in a still more striking
manner, by pouring ether on the surface of water
in flat vessel When the receiver placed these is
exhausted the ether will boil in consequence of the re-
mOva OF the atmospheric PRESSURE and rapid evapora
We
shall thus have the singular exhibition of liquids one
resting upon the other the one boiling and the other eez
ing at the same moment: and, after the lapse OF few mi
nutes, one altogether disappearing in the form of vapou
while the other solidItes in the form OF ice.
A beautiful experiment conrved by Leslie, in
which water is frozen this principle A shallow yes
sell containing water placed under the receiver OF
air-pump Under the same receiver is placed large flat
dish, containing strong suphurc acid The receiver is
now exhausted as rapidly as possible by the pump, and
Immediately the evaporation of the water takes place
Ii the phurc acid present. the space within
the receiver would be saturated almost nsananeously
with the vapour OF the WATER and all further evaporation
would be stopped; but the phuc acid, being itself
subject TO sensible evaporation, has besides strong afin
ty for water, by virtue OF which it attacks the aqueous
water vapou, and causes it to be condensed its
As fast therefore, the evaporaes vapour is
seized upon by the suphurc acid in the large DISH and
the space within the receiver is still maintained vacuum
so that the evaporation OF the water continues rapidly
in the first instance. Now, the heat necessary to give
the vaporous form TO the water only be received from
The water itse which remains in the dish; and there
fore, II must undergo rapid depression of temperature
IL will speedily fall TO the temperature 80 degrees
and in few minutes will be frozen By this process
conducted under favorable circumstances Leslie was not
only able TO freeze water but to CONCEAL mercury and il
is said that he produced cold of 100 degfees
The property which this beautiful experiment. found
ed not recommended alone by the surprise and pleasure
which its result always produces; is susceptible of
iu application in chemistry when il is necessary sepa-
rate water from liquids which heat would decompose and
to dry animal and vegetable substances without exposing
| them to Reorganization.
| USES OF Non -CoNDUcToRs-A silver or metallic
tai, while porcelain teapot always has porcelain
die The of hiss that metal being good conduc-
tor OF heat the handle of the silver or other metallic tea
pot would speedily acquire the temperature the
water which the vessel contains and it would be impos-
sibe TO apply the hand TO il without pain On the other
hand, II is usual TO place wooden ivory handle
metal tea pot These substances being bad conductors
heat the handle will be slow TO take the temperature Of
the metal and if it do take il, will not produce the
same sensation Of heat in the hand. handle apparently
silver, is sometimes put silver teapot but il exain-
ed it will be found that the covering only silver and that
at the points where the handle Joins the vessel
small interruption between the metallic covering and the
metal OF the tea pot itself, which space is sufficient
rupt the communication Of the heat the silver which
vers the handle In porcelain tea pot the heat is slowly
transmitted from the vessel 10 lis handle and even when
Is transmitted; the handle, being bad conductor, may be
touched without Inconvenience kettle which has a me-
al handle cannot be touched when filed with boiling wa
ter without covering Of soma conducting substance
such as cloth paper while with wooden handle ma
be touched without Inconvenience. The feas sometimes
performed by quacks and mouBtebank in exposing their
bodies to fierce temperature may be easily explained
the principle here laid down When a man goes into an
oven raised TO very high temperature, he takes
have under his feet thick mat Of straw, WOOL other
conducting substance, upon which he may stand with
mpuny al the proposed temperature. His body is sur
rounded with air, raised, III true, high temperature:
but the extreme enuy Of this 6ud all that por-
ton Of il in contact with the body at any given time to
produce but slight effect in communicating heat The
exhibitor always takes 10 be Of with any
good conducting substance; and when he exhibits the Of
feet produced by the which he enclosed upon
other objects, he takes equal place them in con-
don vrrY derent from That IN which be himself j. plac-