1000000030

T R

T Y.

fing

th~

ben

eo~du!lor)

ha,·ir.g IIruek one particul1.r vein,

near his neck, and follo'A'cd it

throu~h

its minmn rami–

fieati~ns:

fo that the figu re of it aPl'eared through the

P(in. finer than any penci! eould

hav~

drawn it.

.:autions prrfons not to depend upon the neigh–

bourhood of ahigher, or, in al! cafes, a

~elter

eonduél–

or than their own body; finee, aeeording to his re–

peated obfcr'ations, the lightning by no means de–

l~ends

inone undi,ided tflCk, but bodics of miouskinds

eonduél theil' Ibare of it, at

th~

f. me time, in proportion

to their quantilY and eondJéling power.

A grea! number of obfcr,atiolls, relating to the de–

feent of liglnning, eonGrm his theory of the manner of

its afeent: for, in many eafes, it throws before it the

parts of eonduéling bodies, anJ dinributes them along

the refilliog mediuDl through whieh it mull force in

palTage.

Upon Ihis principie it is, that Ihe loogell flantes of

lighrning feem tO

made by ilS forcing into ilS way

pan of the upours inthe airo Oneof the principal re¿·

fons why thofe fldlbes malle

long a rumbling, is their

being oeeafioned by the van lenglh of a v"uum, made

by the palTage of Ihe elcélrie maller. For though the air

collapCes the moment after it has palTed, and the vibra–

tion (on whieh the Cound depends)

~ommenm

at the

Came moment, tbrough Ihe whole length of the traek;

yet, if tbe flalb was direéled tOlVards the perCon who

hears the report, Ihe vibrations exeited at the nearer end

of the traek wil! reaeh his ear mueh Cooner than thofe

cxeiled at Ihe more remole end ; and the found will,

without any repereuffion or echo, eonunue til! al! thevi–

brations have fueeeffi.ely reachcd him.

He thinks that the Aurora Borealis may be this elte'

trie matter performing its eirculation, in fuch a (late uf

the atmofp1lere as renders it .i(¡ble, orapproaehing ?ear–

cr tOthe earth than ufua!.

Stones and brieks IIrue'" by lightning are often vitri–

fied. He fuppofes that fome 1I0nes in Ihe emh ha.ing

beenOruck in this manner

lira

gaveoeea(¡on

the vulgar

opinion of the thunder-bolt.

Signior Beeearia lVas very

f~nfible

thal heat contri·

butes much tOthe phenomena of Ihuoder, lightning, and

rain; but he could not fi nd, by any experimenr, that it

tended to promote eleélricity. He thercfore rather

thought that heat operated, in this cafe, by exhaling the

moillure of rhe air, and !htreby eutting off the commu–

nieation of the eldlrie fluid berween one place and an–

other, particularly between rhe earth and the higher re·

gions of the air, whereby its effdls wcre more vifible.

M'lh.d

~[ftcuring

óflildi/t;:/

and pufo/t/ [mn Ih,

if-

[dI,

lighlning.

EXPF.RrMENTs maGe in elellrieity fir(l g3,e plrilufo–

phm afufplCion rhat themaner of lightning IVas the fame

\Virh the eJeélrie mamr. Experiments aflen••rds made

on lightning obtaincd from theclouds by pointed rods, re–

cei.ed

into botdes, and fubjcélcd tn e.cry tri, l, ha.e fince

proY<d :his fuCpieion tO b: prrfrélly well foundrJ; and

that what:v, r propenies IVe (¡mi in lIdlricit)', are alfo

tbe properties of lightnillg.

This mamr

lightning, or of d.trid:y, is .In cx–

treme fubtile fluid, pcnetr,uing other budrcs, 3,IJ fubliil–

ing m them equzlly dilTufed.

Whcnby any opmtion of art or n' turc, there happens

to be a greatcr proponion of this finid in

o~e

budy than

in another, the body wlrieh has

0100,

will

communieat~

to that whieh has lean, til! the

p~uportion

becom,sequal;

proviJed the difianee between them be not too great; or,

if it is too great, til! Ihere be pl oper conduCtols to con–

vey it fromone tO the orher.

If the communieation be through the air without ar,y

conJuélor, abright lighl i! feen between the bodics, ar.d

a fOllnd is hearJ. In our fmail experiments IVe ,,11 thi,

light and fou nd the eleélrie fpark and

CnAp;

but in lhe

great operations of nature, rhe light is \Vhat we

call1ighl–

. h,X,

and the found (produeed at the fame

ti01~,

thouglr

generally arril'ing Iater at our ears than the light Jo:s tJ

our eyes) is, wirh its eehoel, called

fh,m"u.

If the communication of this fluid is by a eondu{lor, it

m,y be wilhout either ligh t or found , the fObtile fluid paf–

Gng in the fubnanee of the conduélor.

If the eonduélor

good and of fullicient bigncfs, rhe

fluid palTes through it IV,thout huning it. lf othcrlVife,

it is damaged or de(lroyed.

AII metals, and water, are good cohJuélors.-Orher

bodies may beeome eonduélors by hati ng fome quantity

of water in them, as wood, and other m",eri,Ils ufed in

building, but not having mueh water in them, they are

not good conduélors, . nd thcrefore areoften d"maged in

the opcration by lightning.

GlaCs, wax, filk, wool, hair, feathers, aod eveo wood,

perfetlly dry, are non-conduélors: that is, they refill in–

Headof faeilitating rhepalfagc of thisfubti le fluid.

When this fluid /'" an opportunilY of palling throllgh

t\Vo conduélors, one good and fullicient, as of metal, the

other not fo good, it pa(!i s in the ben, and wil! follo IV it

in'"y direélion.

The diOance at which a body cha rged wirh this fluid

will difcharge itfelf fudden/y, Oriking through the air in–

tOanother body toat is not ehacged, or not fo highlychar–

ged, isdiffi:rent

aeeordin~

tothe quantity of the fluid. the

dim~nfions

anel (orm of lhe bodies themfelvcs, and the

Hate of the air betlVeen them.--This dillance, \l'hate–

ver it happens to be between any tlVO bodies, is cJlleJ

their

j),.WIIg dif/afla,

as till rhey come within that di.

lIan" of eaeh other, no IIroke will

m.lde.

The clouds have oft"n more o( this fluid in proportinn

than the eanh; in whieh cafe as foun·as they come near

enough (rhat is, " ithin rhe llriking diO¡nce) or mm

\\'itha eonclnélor, rhe fluid quits them3nd flrikes into the

mth. A cJoud fully charged with this fluiJ, it' fo hit h

as to be beyonJ the flriking

dillau~e

frnOl tho ewh, p,f.

fes

qui~tly

without mal:ing any nnire or

gil'in~

litht; un–

lefs ir mt'm with orhcr c1nuds rhar hale I. (s.

T, II rrm, '"" loftyhuildings. as the

row~rs

and fpiref

of ehurehes, bccome COOletimls cu"duélol'S bctwrrn

th~

clouds anO the ea nh : but nut ¡'cing r,nod ones, lhat is,

no' con.cying the fluid freely, th,y "e of,en damaged.

DuildinJs !1m havc tl,..ir rours

rOI'cr~d

lI'ith

/w/

othcr metal, a"d f¡'llm! of

me;:~

comir.I\·:J [¡o:n tite :ouf

mro