HE 
they are eminently aifpoted to radiate heat. In fad this 
eel is probably proportional to their capacity for heat. 
y: Screens of glafs, paper, tinfoil, &c. being placed 
between theradiating body and the reflector, were proved 
to eno te the radiant heat completely ; but non ated 
the direct radiant heat, ia time ™m 
from hot w not feem capable of being tran 
mitted thro hal, ike the folar heat. sthly. Radiant 
heat faffers 1 no fenfible lofs in its paflage 
6t 
aed heat diminifhes eee as the ‘diftance 5 ; thatis, the 
denfity of heat refle&ted from a concave mirror in any point 
of the focus, i is inverfely as the diftance of the hot body 
from the mirror ; whereas in regard to ae the denfity 1s 
fr 
that of light, aaa nearer to the wefleét or, ‘The bes ating effect 
s rapidly in os but flowly in going award 
towards the reflector. efe are new and unexpected fas, 
avhich, if eftablifhed, will afford fome remarkable differences 
betwixt heat and light. 7thly. The quantity of heat which 
a ftrongly radiating furface throws off, is fomewhat more 
prt that which is carried off by thea tmofphere according 
to Mr. Leflie ; but Mr. Dalton ere it to be fomewhat 
For the law obferved in the cooling of bodies, fee Re- 
FRIGERATION. 
. 2. The flow and ical communication of. heat from 
particle to particle, isa phenomenon which appears under 
two very different ts of view, as we contemplate it in a 
fluid or folid body. In a fluid, the particles are no fooner 
; — is by radiation, asin the former pa is not very ealy 
o decide ; perhaps the flownefs of the progrefs of heat may 
depend ale = gre number of fucceffive radiations from 
— to 
Be poeta of heat. - 
ae Senfible Hxat.—This phrafe was lately commo 
ft writers on the fubjec of Baise and is itill ufed by 
fome ; ; — heat is added to o a body, A 
@ proportionate change of te eres is a din 
“body, then te heat is faid to be free or /enfible to the se 
eS 
Lata Hi EAT.—This phrafe was firft ufed by Dr. Black. 
% ‘Jt was fuggeited from the difco overy, that a large quan- 
~tity of heat fometimes difappears, or is abierhed by a body, 
e of temperature. Thi ns 
~without any incre appe 
when _—- as a from a folid becomes end. or from a Faget be- “4 
0 bodies of the fame ~ 
rm: and fometimes, when tw 
perecurstnaneent a great de 
but whena due portion : eat 
pre bodies, the tem 
cold is produced, 
n of heat is aoqiued from. the fur- - 
emperature is reftored. The heat 
in thefe cafes is-called /atent.. The expref- — 
eb ae proper and unexceptionable in the firft — 
as 
A T. 
lity, be aca boibined with the body, and on this 
accoun e different tee the fenfible or common 
heat which Sie bodies give o 
be erature. This notion night 
ing experience has fhewn it to be The 
heat fo abforbed has been oth in moft, if not all cafes, to 
capacity th -formed body 
for heat, “and is therefore ‘preeiiely3 in the fame fituation as 
the reft of the heat inthe body. “The phrafes frze and ons 
file heat, and Jatent heat are now therefore difufed b 
moft diftinguifhed writers, as calculated to fuggeft Hah: 
views of the fubjeét. 
nimal Heat.—The excefs of temperature which certain 
animals Sg above that of the furrounding medium is called 
animal hea he caufe of this has been an objeét of 
enquiry iba gt phyfiolo ifts. We owe the princi ipa ds 
cidation of this obfcure ubjeéct to the modern difcoveries in 
pneumatic chemiftry, and in the general principles of heat, 
om ‘and more particularly to the fagacity aiid as acute peri 
of the late Dr. Crawford, whofe ex on animal 
heat, andthe inflammation of tg ie atiie: may be 
ogee as forming an era in phyfiological and chemical 
cience. 
The temperature of the vital s of the human isat 
a medium shone tee Tt is ree be 
much the fame in all <Htons and climates ; but during an 
flammatory fever it has been known to be elevated 10 or 12”. 
everalof the wa rm-blooded animals poffefs nearly the 
temperature as man. as is well known, I 
rabove the common 
his t 
3 
emperature of the atmofj yhere ; it 
‘becomes an object of en Gy then, what is th f 
heat in animals, which fupplies the conftant watte occafioned 
by the cooling power of the atmofphere. a jeCtures 
and opinions on this hea een va and moft of 
a rio 
- themimprobable, as was likely before the propetties of heat 
: ; Some have afcri ibed ani- 
and elaftic fluids were developed. 
mal heat to the attrition of the particles of the 
againtt the coats of the arteries nf the courfe of circulation; 
others imagine the fource of heat to be in the change the 
aliment undergoes in the procefs of ae Sg: ; others fup- 
Sabot colar 
fai train of euleate and ex ce, of w 
cay abitrac, eth deepens of as ap eet = 
Skee rsree' have induced, _ See Crawford on peg: ‘Heat, 
2d edit. 
The cireumitance that warm-blooded animals are 
‘nifhed with lungs, and that, in breathing, carbonic aci 
pened could not fail to fugg ggefito De ” Black an anslogy 
‘betwixt the combultion of charcoal and i org ; a 
‘following up the views which his difcoveries on 
d Crawford to anticipate 
g the phenomena of what he called at 
eel that the appearance or difappearance of 
rather temperature, was owing to a change in 
capacities of bodies, — by chemical or other 
whereas the language of Black was calculated. to conty 
-the notion of heat: eatlihig 4 
Se 
ointed out b ber oF 
paren re ant gs whieh he Yt oports by aoe 
of 
have been 2 em, Se 
otherwife. 
