The enquirer. [volume] (Richmond, Va.) 1804-1815, 1805-04-16


"Thoie who have ieen negroes oxpofed M
ked 10 the fun's rays in hot countries, muit have
obierved that THEN il>;ns, in that E.nat;on, are
always filming. An oil exudes from their fi;in,
which gives !. that Dining appearance, and the
pcliihed TuriaSe Of that oil reflects the iuns ca
loriic rays. Ii the heat be very interie, fveat
makes its appearance al the iurfaCe Of The kin.
This watcry R'id not only reflects very power
fully the ca'orihc rays of the Cun, which fall on
its pohed 'nrfacc, but alfo, by it's evaporation,
generates co1. When the Fun is gore down.
the icei; dudprears; the oil at the fu,fsce or
the fin retiros ;uwarts; and the iSin is left in
Gate very favourable to the admiilion of thofe
feeble irigorihc rays which arrive from the
neighbouriug ohieGis.'
As reiult'ng from other experiments the
Count iniers that the eydrmtb OF any kind OF
iubGance uied as clothing, or its power Of pre-
venting our bodies from being cooled b. the
influence OF iurr0undiug colder bodies, depends
much on tie beliB efi.J Jio-faee: for upon care
full examination. it will be found that thofe liib-
ftanceS which fuDply us with the warrnet CO.
verings, furs, feathers, fix, &c. are not only
limooth, but highly polilied: il viii ALTO be
found, other circumstances being equal, that
thoie iubftances IRE the warmeh which are the
hnest, or which competed of the grea;ec nunhe.
OF fine polihed detached threads fbres The fine
white filming fur Of Ruil-u hare Is much werner
than coorie hair; and fine liik pun iror the fix
worm, is warmer than the fame ilk twiled together
INTO coar'e threads
Formerly Conn; Rumfsrd coniidered the warmth
Of natural and artificial clothing depending ey;nei-
e2aI!y on the ohface it oppocd the ,rotiors of
cold air hy which the hot body i, iurrounded but
, b. pateu; examination of the iubjea, he is nov.
convinced hat the efficacy of radiation is much great
er tia, ne had iuppoed 1t to be- Only very fnar
part Of the heat which hct body appears to loir
~ he air
to that huid much greater portion Of being
nlunicatsd TO other Gsrrounding bodies at diance
" the ny Potheis of the communication, O. rather
g."s.l!o7 OF heat and cold by radiation as explained
~ this philosopher, be true it WILL he tonceives
BILE aim to iiluae in Satisfactory mariner what has
been called the no'-los51e7 power of traufparert
fluids, with rere9 heat for if heat be reilly COM
unlcated, excited, in e thus delcribed, It
Is evident that .,jte7y i,44 lrH fluid receive
heat only at It's iurtace and consequently that heat
cannot be propagated in lc fluid by communicate
on from particle OF tie fluid to another.
1t Cannot be afcerained whether any Of the fluids
with which acquainted a,e terjt17i, f,aa,ba-
rents but pure water aud air, and mon other fluids
which are traniparnt the light, poheis, probably
high degree OF trariparency in regard caioriiic
and tTigoritc rays; give a free pai,ags to them
when they have paIed their Furnaces. AN e.
ven or Po'ihed uracc has been found to facilitate We
ry much the reelection Of the rays of ght the Count
/,
equal tendency to facilitate the reflection of calorc
and ifigorifc rays ?"
~ icme experiments wild. large cylindrical veIsls,
where they were expoied mixed to cool in the air
ther Furnaces polilhed, and they were long time
IN cooling But wheu the llriace of the vellel wa.
5aekened, covered with other fubfances The vef-
iei was found cool more rapidly large pro
portion of the irgoriic rays from the flrroundinc
colder bodies were, i'll the former cafe, refeed at
the pnhcd fagface OF the metallic vellel but, in
the latter cafe more of them were Afforded
When large drop of water rolls about, without
being evaPorated upon the fiat furf.ce Of piece of
fed-hot on the iurfaee of the drop poEc; and the
caoriiic rays being molly rejected water isheated
very Ate. IL the iron be ieE bot, the water pene-
trates the pores OF the oxide which the nsta
the drop ceafes 20 have poiihed furface-ac1uires
heat very rapidly-and /: foon evsporated
fadrcp Of water he placed clean and polh-
ed flriace 81 metal 10 eafy BE as iron it
sd retain iphcIcal form and poihed furface UNI
der lower degree Of temperature than OH iron.
VI large drop Of he put carefully into
clean FLYER ipoon previouy heated very hot the drop
viii iupport the heat comfortable time but after
tie ipoon has been iuered to cool down nearly to the
temperature o. boiling water, drop of water will
be evaporated initaItaneouHy. Hence it is inferred
that under high PeratureS, air attracted by metal
10 much more hrongly than water, that even the
weight of drop of water is fuffcient to force
away the ilratum of air which covers, and adheres to-
the furlace @! Il metal which the drop repoies :;
but, at lower temperatures, this does feem to he
the cafe.
We nall conclude this part Of the Counts enquiries
with an account Of an experiment, eay repeated aud
which he made with view of invchigatng the caufe
of the flow evaporation of drops OF water placed OH
hot metals.
EHPoimsm.-Takng clean poGhed FLYER fpoon,
he blackened the inhde of it with the fame of wax
candle; and then put large drop Of water into it
which rolled about the fpoon, without wetting its
blackened iurface. He then attempted to make the
water boil over the flame of the candle, but found il
impolfible. IF the bowl of the fpoon were touched
With the finger hitting noiie announced that it was
extremely hot, but the water remained quiet in the
'poon, without being eVaporated. Having in vain
attempted make this drop of water boil he poured
the drop into the palm OF his hand which was only
warm though the handle of the Gpoon was too hot 70
be held even with ievcral Hrappings of linen about
BY holding the lPoon, with pair of tongs, ever
the flame OF the candle for longer time the drop
gradually 6aqcedH /o,m, became les and at length e.
vaporated from being lphercal aud lucid, it took
oblong form, and It's lurlace became obfcurs and
when it evaporated it left Kin behind it, which
competed of the particles Of black matter that had
by degrees attached themlcves to its furface, and
which, probably, had contributed not little to its be-
ing at lalt hcaTed and evapora.ed
The change IN the form Of the drop Of water, and
the gradual lois gifts lucid appearances led the Count
to iupect that ii had turned round during the expert