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H E A

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H E A

h~s

been junIy obferved, by Come of our modern

philofophers, th:1I a8ual or abColute heat, is to fcnfible

or relalive heal, the fame as motion is 10 velodlY: for

abfolute heat is nothing bUI Ihe whole molion of all

Ihe pans of the ignitcd body; and Cenfible or relative

beat,

refpeas only the comparative velocity of Ihe

paru. Thcs, equal bulks 01 mercury and water fei

in a fand·heal, where the heal of the 6re may be uni–

formly communicmd 10 bOlh, will acquire in equal

rimes equal'degrees of abfolute heal: bUI Ihe relative

btat of the

\~ater,

or thal which is

f~nGble

10 Ihe fin–

ger, will be near 14 limes as greal as Ihal of Ihe mer–

cury, becaufe the water, having 14 times a lefs quan·

tity of mmer, will admit of velocity fo much in pro·

portion greater.

Ag,in, if mercury and water have t,he fame rela·

tive or fenfible heal, Ihal is, if both are heated in fuch

maoner as to caufe an equal afcenl in Ihe Ihermome·

ter, tben a quaolity of mercury will heat 14 times as

much waler as lhe fame quaolily of water will do ; or

il will make the fame quanlily of cold water 141imes

houer lhan the fame quantilY of hOI water can. AII

which is eafy to be (hewn by experiment, and abun–

dandy proves, Ihat heal and 6re are wholly owing 10

the velocilY of the pam of Ihe healed or ardenl body:

onwhich Ihei>ry lhe various pheoomena ofheal,cold, 6re,

burning,

&c.

are rationally accounted foro For, firll,

we are 10 conGder, Ihat cold and heal are only como

parative lerms, or thal Ihe fame Ibing may eilher be

too

hot, or 100 cold, according 10 the relalive idea or

/landard.dcgree. Thus, ice ór fndw is faid 10 be

cold wilh reCpea 10 the finger, bUI ice or foow is

warm if compared 10 a freezing mixlure;

that if

(as we commooly do) we make the hand or aoy part

of !he body Ihe llandard of heal or cold, or the lerm

of compariCon; Iheo il is evident,

If Ihe parts of

aoy body, applied lO the haod, have Ihe fame velocity

the pans

the hand, fuch a body we oalurally

pronounce is neither hOI nor cold.

the particles

of !he body have a

~reater

velocity Ihan thofe of

the hand, we pronounce it warm, if Ihe excefs be

fmall; but hot, if il be greal.

If Ihe velocilY of

the pam of Ihe body applied be lefs Ihao that in lhe

hand, Ihe Cenfalion then is whal we call cold, which

alCo may be in various degrees.

Hence it is plaio,

there cao be no fuch thing as abfolute cold. but where

the particles of m¡¡¡er are abColutely quieCcenl or al .

rell.

Hence alCo, there can be no Cuch thing as

abfolute heal, becauCe no degree of velocity can be

alligned bUI a greater is lIill allignable, lill we come to

in6nity, where we are quite

1011,

as haviog no idea of

in6nite velocity or heat.

From this theory of heat and cold we may

cooclud~,

Ihal there is no body in oature whofe pans are not

motion, in Come degree, Gnce we have yel beeo able

to difcover no ultimate dcgree or limit of cold; and

if aoy fuch thiog were tO be found in oature, it is like–

Iy!hat it would be as impollible tO bear or endure the

tdl, as any extreme degree of heat; both heat and

cold naturally lending to denroy the animated part,

or tdl, in tbe extreme degrees : cold, by defirDyillg

VOL.

II.

NUOlb. 59.

¡he vital mOlinn, Qnd fixing lhe pan rigid and inflexi–

ble; but he. t, by pUlling lhe parrs into 100 great

gitation, caufiog agreater velocityof thefluid" and dilJi·

patioo and a force of teofion in lhe fol ids bey?td

what lhe natural 11 ate

the body caD

~ear;

and there.

fore it will ioevitably denroy it.

HEAT,

jo the animal

~conoQly,

known by the Ce.

veral names of natural heat, vilal heat, innate heat,

and animal heat, is commonly fuppofed to be tha.! ge·

n6med by the amition of the pans of the blood, oc–

cafioned by

Íts

círculatory motioo, efpecially io Ibe

artenes.

To what organs or operalions, the hm of the hu–

man body, and olher animal bodies, is owiog. is hi–

Iherto eXlremely doublfu!. The opinions that at pre–

fent prevail are,'

That the heat of animal-bodies is

owing to lhe amition betwixt ,the arterie, and ¡he

blood.

That the lungs are the fountarn of this

heat.

That the attritiorr of the pans of the Colids

on one another produce il.

That it

owing to

lhe mechanical amitioo

th<particles of our fluids.

To IVhich opioi.ons Dr Ste.eofon of Edlnbu'gh add–

ed a 5th,

viz.

Thal whole procefs by IVhich our ali.

ment and juices are confiaody undergo:rig Come alter.

ation.

The reaConings io favour of thefe fevera! opinions

may be Ceen at large, as !aid dolVo by the above·meo.

lioned author in an e{[ay on the caufe of aoimal·heat,

in the Medical Err,ys, vol. vi. The chief arguments

io favou r of the

fidl

opinion, are, th:.t if ao artery

lied, or cut, the part to which it goes turns cold ;

and on the ceafing of the pulCalion of the arterie¡, cold

aod death follow. An increare of hm attends ahrilk

circul;tion, and a languid circulation i, accompanied

with a fmall heat. One who burns io a fever, or i$

h/¡t with exercife. has a full and frequenl pulfe. lo

cold faintings, dJlorofis,

&c.

lhe pulCe is Cmall and

/low. To theCe they add, that the thermorqeter (hews

Ihe arterial blood 10 be a lillle houer tbao Ibal of lhe

vtins.

This is accounted for from the cooica! figure of the

arteries, from their ftuxes and branches into exquiG,e.

Iy Cmall capillaries; whence the refinance, aod confe.

quendy,he amition, mull be grm, from !he oumber,

Hrenglh, and e1anicily of the;r COal!, from!he propel.

ling power of the hmt, and their nroog refinance_

Fromall theCe it i, iofmed, lhat the particles of blood

perpetually geuing oew motions,

diretlion~

aod ro.

tations, are menuated, condenCed, have their angles

grinded off, aod are made homogeneous: hence, il is

faid, follows the fluidity, recj. colour, and heat of the

mafs, IVhich is here perfetled.

The fecond opinion is, tbat tlle luogs are the foun.

tain of heal in the human body. AII thal has beeo

faid for lhe blond's being heated in the arteries is ad.

vanced to prove this hypothefis, IVith conrlderable ad.

ditions,

viz.

that in the lungs the blood-veJl'e1s emy

where Rttend, divide. and Culídivide, along with the

ramificadons of the winJ,pipe; and as lheCe are perpe.

tually changing lheir filUatinn and form, becoming

longer or

fl¡~ncr,

making morc acute or more obture

8 K

angles,