1000000030

yirlcis : for then ys of light come to us fromthe fun,

unnlixeu wllh

~ny

of thn grofs, feculent, or t rrefll i·

'~I

mmer,

f~und

in culinAry and fubterranean Gres :

but, allowing for Ihis"i[,rence, the eIT<l1s of the fo·

IIr fi,e appw the fame as thofe of culinary fi,e.

w. tOexanline the elTdts of fubtemneous 6res,

\Ve

OI~1I

6nd them the

f~nlc

wilh thofe produced

cuhnary 6re. T hus, burnt coals, cinders, and

meh.d minerals, are thrown up by Vefuyius and olhcr

burning

mount.in

,. W"m

n,phritic~1

eKh lations,

natur¡) hot

fprin~s,

Oeams, vapnurs, fmoh ,

Ó,.

lIe

found in fcvml pans of the Rlohe, riling nearly

iJl

the fame nlanner as if Ihey weoc produced by Ihe hm

of a furnace. Whence it appean, that fubtemncous

fi,es aoe

the fame nature wilh the culinAry.

men gencrally aflix lO Ihe word 6re, a compleK

idea of burning. liglll, heat, mehing,

6,.

this od

thould be analyfed, in order tOfce what p¿rts are ef.

fential, and lI'hat precatious or arbitrary.

We frequently find Ihe eITcéls of lire produced

whm no vifible fire appearcd. Thus Ihe fingelS are

eaGly burot

Rn iron heated below'tlle degree of ig.

nition, or fa as tObe no lI'ays viGbly red·hot or nery:

whence it follolVs,

th~t

the eye is no judge of 6re.

So likewife the touch siyes no pofitive notice of

any dcgm of 6re belo\V the natural hm of the bally,

or any fo grm as tOdeO roy the organ.

Again. the eff<lls of fi,e are oftcn produced wilhout

nfty

ooani~

Ofigns of burning. mehing,

Ó,.

as in e·

npomions,

6,.

If this method of exduGon and re·

jea ion were purfued to

its

due lenglh, \Ve Ihould

perhaps 6nd no critcrion, infjllible mark, or charac·

m iOic of

~re

in general, but that of a particular mo·

tion Oruggliog amons the minule pam of bodies, and

lending lO throw them off at the furfaee. If this

Ihould prove the cafe, theo fuch a motion will be Ihe

form and cITence of nre; and which, being prefent,

m kes nre alfo prefent : and, when abfent. mal:es nre

alfo abftnt : whence to produce 6rc, and produce thi.

motioo in bodies,

II·m

be one and the fame thing.

The grtat and fundamental

~iff(fence

in refpea

to the nltUre of 6re is, whetber il be originally fuch,

formed thus by the Crmor himfdf at the beginning

of things ; or whether it be mechanically producible

from other bodies, by ioducing fome ahe..tiuns in tloe

puticlu Ihmof. The former opinion is mantained

!ly Homberg. lloerbdi,e, the younger Lemery. and

~'Gravefande;

the Imer is chicfty fupported by Ihe

Englolh p' ilofophm, lord Bacon, !>Ir Ho}le, and Sir

Huc ewton.

Ilacon, io the treatife De Forma

C~licli,

deduces,

from asreal number uf paniculm, thit hea! in borlies

other than motioo fo aod fo Clr,'Umfianctd

that to produce heat in a body, nOlhing is required but

tOexcite a certlin motion

Ihe paru thereof

Hoyle

f~conds

him In an exprcfs Ireauf. of the me·

chanical origin of hm and c,,1d,

~nll

mainlains the

(.OIe do..'lflne wnh ncIJ obfcru.iuns ano expwmcnu;

"' a fp:

c.n.cn

hich, we

OI~1

he.r gil'e the

t~·o

f;lIowir.;:.

lo ¡JI: rrcxlu!'iuo cf h:zt,

fl~'~

tloat able rhilofo.

phtr, ther

app~rs

oothing on Ihe plrt eilher of the a.

gent urpJtient,

~Ut

mOlionandits

o~tural

eITclh. Whcn

a I¡uitb brill"y hanllllm a piete of iron, the metJ

thm by bccomes exmdingly hot ; yet there is nothoag

nljkc it fo, except the forcible Dlodon of the h m.

mer imprdling a vehement and vatlouOy dmrmoned

agitatoon on the fmall pm s of the iron, which, be,ng

a cold body before, growl, by that fuper.induecd

commotion of iu fmall pans, hot : 6rfi, in a more

loofe acceptation of the word, with regard to fome.o.

ther bodies, compared with which it was caId hofore;

then feoGbly h,.t, becaufe this agilation furpafl"'1 thu

of the pointS of our6ngers ; and in this infi,oce oflen–

times the hammer and ¡ovil conunue colJ afler theo–

pendon; which fhe ws, tbat the heal aequired by the

iron \Vas not éommunicaled by either of thofe impl..

ments, as hw; bUI produced in it by a motion, srC<!

enough ílrongly to agitate the pans of fo (n,,1I a body

as the piccc uf iron, without being able to have Ihe

like efl'd l upon fo much gremr m¡fl'cs of nletal as Ihe

hammer and the anyil: though if ohe percuflions werc

oflcn and brilkly renewed, and Ihe hammer

fmlll,

this alfo might be heat,d: whence

is OOt nmfl'ary

th" a body ilftlf be hot togi'e hm.

2 .

If a Iarge nail be driven by a hammer in

apbnk

wood,

it will recciye femal IIrokes on in head

before it grows hot ; but lI'hen it il once driven tO tl'e

Ilu d, a few firokes fuflice tO give it a confidmble

heat~

for while, at emy blow of the hammer, the

nailenters fU llher illlo the wood. the motionf'oduLCd

il chicfty progreflive, and is of the whole n.i tending

one way; but wheo that motion ceafel, the iml'ulfe

given by the firoke being unable tO dr;ye the nall fur·

ther

00,

or break it. muObe fpeot in making a ...i·

OUI, ,<hement, aRd intenine commntion o( Ihc puu

amoog themfelyes, wherein the nllureof helt conroO,.

Agreeable

this is the opinion of Sir Ifm

1""

Ion, \Vho conceives Ihat frofs bodies may be conn md

iDlo lighl, bythe ¡gimionof thtir pmicles

Ind hght,

again, inlo grofs bodies, by being 6xed thm ln.

On the other hand, M. Homberg. in hll

Err"

SouITre Principe, holds, that the chemicll prinCIpie,

or e1emcnt fulphur, which il fuppofedone of the fimple,

primary, prc.exiOenl ingrcdilnts of all nllural boJoe ,

is real 6re, anJ coofequently Ihat nre is coenl ..."h

ballits.

s'Gravef~nde

goes on much the fame pnn¿ple:

fire, Iccordlng tO him, eOlcrs the compofiuon of

~II

bodics, is cofltained iD aOI bodies. and ma be (epI'

ralul or procured (rom all bodi.., by rubbing them

ag~lnll

eaeh olher ; And thus putling tlocir firein mO'I(If1:

but fire, he adds, u by no meaos gcncnleJ by (u¡h

fUolion

Mr Lemery. the

youn~er.

agrm lIith Ihe(e

aUlho" in a{ferting thol

~bfolule

anJ

in~lnC!lblc

nl'

ture of (¡re: bUI he

e~tcnJs

it fmhcr.

conrent·

td tOcon6ne

al an d.ntent

boJi,., he er.

.tc~,our.

to nleW,

.th~t

equ.ally

diITuf~,II~ll'u.;h

,11 fr"c,

and thar

u prefent In all rl.rtS; In the 1'0rJ f?m

between bvdics, as wdlls in tbe rDftn6b!e rntcrlh«'

Lclll'een their rms.

n il