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EXPERIMENTS
AND
OBSERVATIONS
ON
ELECTRICITY,
M A D E AT
Philadelphia in America^
BY
Mr. BENJAMIN FRANKLIN,
AND
Communicated in feveral Letters to Mr. P. Collinson,
of London^ F. R. S,

LONDON:

Printed and fold by E. Cave, at St. John\ Gate.
(Price 2s. 6d.)

1751*

>
The PREFACE.
IT may be neceffary to acquaint the reader^ that the following obfervations and experiments were not drawn lip with a view to their being made pithlick^ hut were communicated at different timeSy and moji of them in
letters wrote on various topicks^ as matters only of private amufement.
But fome perfons to whom they were read^ and who had
themfelves been converfaiit in eledlrical difquiftions^ were of
opiniony they contain'd fo 7nany curious and interefting parti-
culars relative to this affair^ that it wotdd be doing a kind of injujiice to the publicky to confine them folely to the limits of a private acquaintance.
The Editor was therefore prevailed upon to commitfuch extracts of letterSy and other detaclod pieces as were in his hands to the prefsy without waiting for the ingenious authors permiffon fo to do ; and this was done with the lefs hefitationy as it was apprehended the author s engagements in other affairSy would fcarce afford him leifure to give the publick his refleciions and experiments on the fubjeSty finiJUd with that care and precifiony of which the treatife before us Jhews
he is alike ftudious and capable. He was only apprized of
the fiep that had been thus takeny while the firft fleets were in the prefsy and time enough for him to tranfmit fome far-
ther remarksy together with a few corregions and additions^
which are placed at the endy and may be confidted in theperufaL The experiments which our author relates are moft of them
peculiar to himfelf-y they are conduBed with judgmetity and the inferences from them plain and conclufive , though fometimes propofed under the terms of fuppofitions and conjectures
And indeed the fcene he openSy ftrikes us with a pleafing
ajlonijhmenty whilfi he conducts us by a train of faBs and judicious reflectionsy to a probable caufe of thofe fhanomenay
which are at once the moft awfuly andy hithertoy accountedfor with the leajl verifimilitude.-
He

PREFACE.

He exhibits to our confideratton^ an invijible^ fubtile mat-

ter^ dijjeminated through all nature in various proportions^

equally unobjerved^ and^ whiljl all thofe bodies to which it pecu^

Hark adheres are alike charged with it^ inoffenji've.

He JhewSy

however ^^

that if an unequal dijlrihution is

by

any means brought about ; if there is a coacervation in one

part of fpaccy a lefs proportion^ vacuityj or want^ in ano-

ther ; by the near approach of a body capable of condu£l-

ing the coacervated part to the emptier fpace^ it becomes

perhaps the mof formidable a?id irrefiftible agent in the uni-
f verfe. Animals are in an Infant ruck breathlefs^ bodies

almoft impervious by any force yet known ^ are perforated^ and

metals fufed by it, in a moment.

From the Jimilar effects of lightening and eleBricity our

author has been led to make fame propable conjeBures on the

caufe of the former \ and at the fame time, to propofe fame rational experiments iji order to fecure ourfalves, and thofe

thirtgs on which its force is often diredied, from its perni-

cious effeBs-y a circuniflance of no fmall importance to the

publick, and therefore worthy of the utmoft attention.

It has, indeed, been of late the fafaion to afcribe every

grand or umfual operation of nature, fuch as lightening and

earthquakes, to eleBricity -, not, as one would imagine, from the

manner ofreafaning on thefe occafons, that the authors of thefe

fchemes have, difcovered any ccnneBion betwixt the caufe aiid

effeSi, or faw in what manner they were related *, but, as it-

would feem, merely hecaufe they were unacquainted with any

other agent, of which it could not poftively he faid the con-

nection was impojjible.

But of thefe, and many other interejling circum/lances, the

reader will be more fatisfaBorily informed in the following

ktters^ to which he is therefore referred by

5n&rEDIT0R.

DSI

LETTER I
FROM
Mr Benj. Franklin^ in Philadelphia.
To Mr Peter CoLLiNsoN, F.R. S. London.

SIR,

July 28, 1747.

HE neceffary trouble of copying long

letters, which perhaps when they come to your hands may contain nothing

new, or worth your reading (To quick

is the progrefs made with you in E-
leftricity) half difcourages me from

writing any more on that fubjed:. Yet I cannot forbear
adding a few obfervations on M. Mufche?ibroek!s won-

derful bottle.
B

The

.

:

2

Mr B, F R A N K L I N 's

1 The non-eledtric contain'd in the bottle differs when
eleftrifed from a non-ele£tric eleftrifed out of the bottle, in this : that the eleftrical fire of the latter is accumulated on its furface^ and forms an eledlrical atmofphere round it of confiderable extent : but the eleftrical fire is crouded into thefubflance of the former, the glafs confining it.
2. At the fame time that the wire and top of the bot-
' tie, &c. is eledlrifed pojitively ov plus^ the bottom of the bottle is eledlrifed negatively or minus^ in exaft proportion : /. e, whatever quantity of eledlrical fire is thrown
in at top, an equal quantity goes out of the bottom. To underftand this, fuppofe the common quantity of Eledri-
city in each part of the bottle, before the operation begins, is equal to 20 ; and at every ftroke of the tube, fuppofe a quantity equal to 1 is thrown in ; then, after the firft ftroke, the quantity contain d in the wire and upper part of the bottle will be 21, in the bottom 19. After the fecond, the upper part will have 22, the lower 18, and fo on 'till after 20 ftrokes, the upper part will have a quantity of eleftrical fire equal to 40, the lower part none
and then the operation ends : for no more can be thrown into the upper part, when no more can be driven out of the lower part. If you attempt to throw more in, it is
fpued back thro* the wire, or flies out in loud cracks thro' the fides of the bottle.
3. The equilibrium cannot be reftored in the bottle by
inward communication or contad; of the parts; but it muft be done by a communication formed without the bot-
tle.

Letters on Electricity.

3

tie, between the top and bottom, by fome non-eledlric, touching both at the fame time ; in which cafe it is re-

ftored with a violence and quicknefs inexprefTible : or,

touching each alternately, in which cafe the equilibrium

is reftored by degrees. 4. As no more eleftrlcal fire can be thrown into the
top of the bottle, when all is driven out of the bottom,

fo in a bottle not yet eleflrifed, none can be thrown into

the top, when none can get out at the bottom ; which happens either when the bottom is too thick, or when

the bottle is placed on an eledtric perfe.^ Again, when

the bottle is eleftrifed, but little of the eleftrical fire can

be drawn out from the top, by touching the wire, unlefs

an equal quantity can at the fame time get in at the bot-

tom. Thus, place an eledrifed bottle on clean glafs or

dry wax, and you will not, by touching the wire, get out

the fire from the top. Place it on a non-eled:ric, and

touch the wire, you will get it out in a fhort time ; but

fooneft when you form a dired: communication as above.

So wonderfully are thefe two ftates of Eleftricity, the

plus and minus^ combined and balanced in this miraculous

bottle ! fituated and related to each other in a manner that

I can by no means comprehend ! If it were poffible that a

bottle fhould in one part contain a quantity of air ftrongly

compreft, and in another part a perfed: vacuum, we know

the equilibrium would be inftantly reftored within. But

here we have a bottle containing at the fame time 2i plenum

of eledrlcal fire, and a 'vacuum of the fame fire ; and yet

B2

the

4

Mr B. F R A N K L I N 's

the equilibrium cannot be reftored between them but by a communication without ! though the plenum preffes violently to expand, and the hungry vacuum feems to attradl

as violently in order to be filled.

5. The fhock to the nerves (or convulfion rather) is oc-

cafion d by the fudden paffing of the fire through the

body in its way from the top to the bottom of the bottle.

Mr The fire takes the fhorteft courfe, as

Watfon]\x^y

obferves : But it does not appear, from experiment, that,

in order for a perfon to be fhocked, a communication

with the floor is necefl^ary 3 for he that holds the bottle

with one hand, and touches the wire with the other, will

be fhock'd as much, though his {hoes be dry, or even

ilanding on wax, as otherwifc. And on the touch of

the wire (or of the gun-barrel, which is the fame thing)

the fire does not proceed from the touching finger to the

wire, as is fuppofed, but from the wire to the finger,

and pafl^es through the body to the other hand, and fo into

the bottom of the bottle.

Experiments confirming the above.
EXPERIMENT I.
Place an eledtrifed phial on wax \ a fmall cork-ball
fufpended by a dry filk-thread held in your hand, and brought near to the wire, will firfl be attraded, and then
repelled : when in this ftate of repellency, fink your hand, that the ball may be brought towards the bottom of
the

Letters on Electricity,

5

the bottle 5 it will there be inftantly and ftrongly attrafted, 'till it has parted with its fire.
If the bottle had an elecarical atmofphere, as well as the wire, an eleftrified cork would be repelled from one as well as from the other.

EXPERIMENT 11.

Fig. I. From a bent wire (^) flicking in the table, let afmall linen thread {h) hang down within half an inch of the electrifed phial (r). Touch the wire of the phial repeatedly with
your finger, and at every touch you will fee the thread inftantly attracted by the bottle. (This is beft done by a vinegar cruet, or fome fuch belly'd bottle). As foon as you draw any fire out from the upper part by touching the wire, the lower part of the bottle draws an equal quantity in by the thread.
EXPERIMENT III.

Fig. 2. Fix a wire in the lead, with which the bottom of
the bottle is armed, (d) fo as that bending upwards, its ring-
end may be level with the top or ring-end of the wire in the cork (e) , and at three or four inches diftance. Then elec-
tricife the bottle, and place it on wax. If a cork fufpended by a filk thread (f) hang between thefe two wires, it will play incelTantly from one to the other, 'till the bottle is no longer -eleftrifed ; that is, it fetches and carries fire from the top to the bottom of the bottle,, 'till the equilibrium is reftored.

EX.

6

Mr B. FR ANKL I NV

EXPERIMENT IV.

Fig. 3. Place an eleftricifed phial on wax ; take a wire (g) in form of a C, the ends at fuch a diftance when bent, as that the upper may touch the wire of the bottle, when the
lower touches the bottom : ftick the outer part on a ftick
of fealing wax (h) which will ferve as a handle. Then ap-
ply the lower end to the bottom of the bottle, and gradu-
ally bring the upper-end near the wire in the cork. The
confequence is, fpark follows fpark till the equilibrium is
reftored. Touch the top firft, and on approaching the bottom with the other end, you have a conftant ftream of fire, from the wire entering the bottle. Touch the top and bottom together, and the equilibrium will foon be reftored,
but filently and imperceptibly 5 the crooked wire forming
the communication.
EXPERIMENT V.

Fig. 4. Let a ring of thin lead or paper furround a

bottle (i)^ even at fome diftance from or above the bottom.

From that ring let a wire proceed up, 'till it touch the

A wire of the cork (k) .

bottle fo fixt cannot by any means

be eledtrifed : the equilibrium is never deftroyed : for

while the communication between the upper and lower

parts of the bottle is continued by the outfide wire, the

fire only circulates : what is driven out at bottom, is con-

ftantly fupply'd from the top. Hence a bottle cannot be

eledtrifed that is foul or moift on the outfide,

>^**»

EX*

Letters on Electricity*

y

EXPERIMENT VI.

Place a man on a cake of wax, and prefent him the wire
of the eledtrified phial to touch, you {landing on the floor, and holding it in your hand. As often as he touches it, he will be eled:rified plus ; and any one ftanding on the floor
may draw a fpark from him. The fire in this experiment palTes out of the wire into him ; and at the fame time
out of your hand into the bottom of the bottle,
EXPERIMENT VII.

Give him the eleflirified phial to hold ; and do you touch
the wire ; as often you touch it he will be ele£lrified minus^
and may draw a fpark from any one flanding on the floor. The fire now pafTes from the wire to you, and from him
into the bottom of the bottle.
EXPERIMENT VIII.

Lay two books on two glaffes, back towards back, two or three Inches diflant. Set the eleftrified phial on one, and then touch the wire 3 that book will be electrified minus ; the eledlrical fire being drawn out of it by the bottom of the bottle. Take off the bottle, and holding it in your hand, touch the other with the wire > that book will be eledlrifed plus ; the fire paffing into it from the wire, and
A the bottle at the fame time fupply'd from your hand.
fufpended fmall cork-ball will play between thefe books
'till the equilibrium is reftored.

;

8

Mr B. F R A N K L I N's

EXPERIMENT IX.

When a body Is eledrifed plus it will repel an eledtrified feather or fmall cork-ball. When minus (or when in the
common ftate) it will attrad them, but ftronger when minus
than when in the common ftate, the difference being greater.
EXPERIMENT X.
Tho', as in EXPER. VI. a man ftanding on wax may-

be eledrifed a number of times, by repeatedly touching the

wire of an eledlrifed bottle (held in the hand of one ftand-

ing on the floor) he receiving the fire from the wire each
time : yet holding it in his own hand, and touching the
wire,tho' he draws a ftrong fpark, and is violently ftiock'd,

no Elefliricity remains in him 5 the fire only pafllng thro* him from the upper to the lower part of the bottle. Ob-

ferve, before the fhock, to let fome one on the floor touch

him to reftore the equilibrium in his body ; for in taking

hold of the bottom of the bottle, he fometimes becomes a

little eleitrifed minus\^ which will continue after the ftiock

as would alfo any plus Eleftricity, which he might have

given him before the ftiock. For, reftoring the equilibrium

in the bottle does not at all affed: the Eleftricity in the man

whom thro'

the fire paffes ; that Eledlricity is neither in-

creafed nor diminifti'd.
EXPERIMENT XL
The pafling of the eleftrical fire from the upper to

the lower part of the bottle, to reftore the equilibrium

is rendered ftrongly vifible by the following pretty experi-

ment.

Letters c?;^ Electricity.

9

ment. Take a book whofe cover is fiUetted with gold ;
bend a wire of eight or ten inches long in the form o((mJ Fig. 5, flip it on the end of the cover of the book over
the gold line, fo as that the fhoulder of it may prefs upon
one end of the gold line, the ring up, but leaning tov/ards
the other end of the book. Lay the book on a glafs or wax -,
and on the other end of the gold lines, fet the bottle electrifed : then bend the fpringing wire, by prefTmg it with a
flick of wax till its ring approaches the ring of the bottle
ware 5 inftantly there is a llrong fpark and ftroke, and the w^hole line of gold, which completes the communication between the top and bottom of the bottle, will appear a vi-
vid flame, like the fharpeft lightning. The clofer the con-
tadl between the fhoulder of the wire, and the gold at one ^nd of the line, and between the bottom of the bottle and the gold at the other end, the better the experiment fuc-
ceeds. The room fhould be darkened. If you would
have the whole fiUetting round the cover appear in fire at once, let the bottle and wire touch the gold in the diagonally
oppofite corners.
I am^ &c.
B. FRANKLIN.

LET-

10 Mr B. F R ANKLIN's

LETTER II.
FROM
Mr Benj, Franklin, in Philadelphia^
TO
Mr Peter CoLLiNsoN, F. R. S. London.

S I Ry

Sept. I, 1747.

IN my laft I informed you that^ in purfuing our eleftriGal enquiries, we had obferved fome particular Phzenomena, which we looked upon to be new, and of which I pro-
mifed to give you fome account, tho' I apprehended they
might poffibly not be new to you, as fo many hands are daily
employed in eleftrical experiments on your fide the water, fome or other of which would probably hit on the fame

obfervations.
The lirfl is the wonderful effeft of pointed bodies, both in
draiving off^ndithrowmgoffxhQ electrical fire. For example: Place an iron fhot of three or four inches diameter, on the
tnouth of a clean dry glafs bottle. By a fine filken thread from the cieling, right over the mouth of the bottle, fuf-
pend a fmall cork-ball, about the bignefs of a marble ^ the
thread

—

Letters 6n Electricity.

ii

thread of fucli a length, as that the cork-ball may reft a-

gainft the fide of the fhot. Eleftrify the ftiot, and the

ball will be repelled to the diftance of four or five inches,

more or lefs, according to the quantity of Eledricity.
When in this ftate, if you prefent to the fhot the point of

a long flender fharp bodkin, at fix or eight inches diftance,

the repellency is inftantly deftroy'd, and the cork flies to the

A fhot.

blunt body muft be brought within an inch, and

draw a fpark, to produce the fame effed:. To prove that

the eledtrical fire is drawn offhy the point, if you take the

blade of the bodkin out of the wooden handle, and fix it

in a ftick of fealing wax, and then prefent it at the diftance

aforefaid, or if you bring it very near, no fuch effeft fol-

lows ; but Hiding one finger along the wax till you touch
— the blade, and the ball flies to the fhot immediately. If

you prefent the point in the dark, you will fee, fometimes

at a foot diftance, and more, a light gather upon it like that

of a fire-fly or glow-worm ; the lefs fharp the point, the

nearer you muft bring it to obferve the light 5 and at what-
ever diftance you fee the light, you may draw off the
— eledtrical fire, and deftroy the repellency. If a cork-ball

fo fufpended be repelled by the tube, and a point be pre-

fented quick to it, tho' at a confiderable diftance, 'tis fur-
prizing to fee how fuddenly it flies back to the tube. Points of wood will do as well as thofe of iron, provided

the wood is not dry ; for perfedtly dry wood will no more

condudl Eledlricity than fealing wax.

C2

To

12 Mr B. franklin's
To Ihcw that points will throw off as well as draw off
the eleftrical fire > lay a long fharp needle upon the fliot^ and you cannot eledrife the {hot, fo as to make it repel the
— cork-ball. Or fix a needle to the end of a fufpended gun«
barrel, or iron rod, fo as to point beyond it like a little bayonet ; and while it remains there, the gun-barrel, or rod, cannot by applying the tube to the other end be eleftrifed fo as to givq a fpark, the fire continually running out filently
at the point. In the dark you may foe it make the fame
appearance as it does in the cafe beforementioned.
The repellency between the cork-ball and the fhot Is likewife deftroy'd 5 i. By fifting fine fand on it; this does it gradually. 2. By breathing on it. 3. By making a fmoke about it from burning wood.* 4. By candle light,
even tho' the candle is at a foot diftance : thefe do it fud~
— denly. The light of a bright coal from a wood fire ; and
the light of red-hot iron do it likewife j but not at fo great
a diftance. Smoke from dry rofin dropt on hot iron, does
^
not deftroy the repellency 5 but is attraded by both fhot and cork-ball, forming proportionable atmofpheres round them, making them look beautifully, fomewhat like fome of the figures in Burnefs or Wbifton^ theory of the earth.

We *

fuppofe every particle of fand, moiflure, or fmoke, being firfl: at-

tradled and then repelled, carries off with it a portion of the eledrical lire ;

— but that the fame ftiH fubfifts in thofe particles, till they communicate it

to fomething elfe ; and that it is never really deftroyed.

So when

water is thrown on Common fire, we do not imagine the element is thereby

deftroy ed or annihilated, but only difperfed, each particle of water carrying

off in vapour its portion of the fire, which it had attraded and attached

toitfelf.

JV.jB. This

Letters on Electricity. . 13

JV. B. This experiment {hould be made in a clofet

where the air is very ftiil.
The hght of the fun thrown ftrongly on both cork and

fliot by a looking-glafs for a long time together, does not impair the repellency in the leaft. This difference between fire-Ught and fun-Hght, is another thing that feems

new and extraordinary to us.
We had for fome time been of opinion, that the elecfbri-

cal fire was not created by fridion, but colledled, being re-

ally an element diffused among, and attradted by other

We matter, particularly by water and metals.

had even

difcovered and demonftrated its afflux to the electrical

fphere, as well as its efflux, by means of little light wind-

mill wheels made of ftiff paper vanes, fixed obliquely and

turning freely on fine wire axes. Alfo by little wheels of
the fame matter, but formed like water wheels. Of the
difpofition and application of which wheels, and the various

phenomena refulting, I could, if I had time, fill you a fheet.

The impoffibility of eledrifing one's felf (tho' ftanding on

wax) by rubbing the tube and drawing the fire from it ^
and the manner of doing it by paffing the tube near a per-

fon or thing ilanding on the floor, &c. had alfo occurred

to us fome months before M.rWatfori^ ingenious Sequel

came to hand, and thefe were fome of the new things I
— intended to have communicated to you. But now I need

only mention fome particulars not hinted in that piece,

witn our reafonings thereupon 3 though perhaps the latter

might well enough be fpared,

A I,

14

Mr B. F R A N K L I N's

A I . perfon flanding on wax, and rubbing the tube, and
another perfon on wax drawing the fire -, they will both of

them, (provided they do not ftand fo as to touch one ano-

ther) appear to be eleftrifed, to a perfon {landing on the

floor ; that is, he will perceive a fpark on approaching each of them with his knuckle.
2. But if the perfons on wax touch one another during the exciting of the tube, neither of them will appear to be

eledrifed.

3. If they touch one another after exciting the tube, and drawing the fire as aforefaid, there will be a ftronger
fpark between them, than was between either of them and

the perfon on the floor.

4. After fuch ftrong fpark, neither of them difcover any

eleitricity.
We Thefe appearances we attempt to account for thus.
fuppofe as aforefaid, thateledrical fire is a common element,

of which every one of the three perfons abovementioned has his equ^l fhare, before any operation is begun with the
Tube. j4y who fl:ands on wax and rubs the tube colleAs

the eledirical fire from himfelf into the glafs ; and his com-
munication with the common flock being cut off by the
wax, his body is not again immediately fupply'd. B, (who ftands on wax likewife) pafling his knuckle along near the tube, receives the fire which was colleded by the glafs
from y? ', and his communication with the common fl:ock

being likewife cut oflF, he retains the additional quantity

— received.

To C, flanding on the floor, both appear to

be

:

Letters on Electricity.

15

be eledrifed : for he having only the middle quantity of

eledtrical fire, receives a fpark upon approaching j5, who

has an over quantity ; but gives one to A, w^ho has an un-
A B der quantity. If and approach to touch each other,
the fpark is ftronger, becaufe the difference between them

is greater ; after fuch touch there is no fpark between ei-

ther of them and C, becaufe the eledrical fire in all is re-

duced to the original equality. If they touch while elec-

triflng, the equality is never deftroy^d, the fire only circu-

lating. Hence have arifen fome new terms among us

we fay, J5, (and bodies like circumftanced) is eledlrifed

B pofitively ; A, negatively. Or rather,

is eledrifed //^/j 3

Ay minus. And we daily in our experiments eledlrife
— bodies plus or miims as we think proper. To eledrife

plus or minuSy no more needs to be known than this, that

the parts of the tube or fphere that are rubbed, do, in the

inftant of the fridlion attract the eleilrical fire, and there-

fore take it from the thing rubbing : the fame parts imme-

diately, as the friftion upon them ceafes,, are difpofed to

give the fire they have received, to any body that has lefs.
Thus you may circulate it, as Mr Watfon has fhewn you ^
may alfo accumulate or fubftradt it upon or from any body,

as you connedt that body with the rubber or with the re-

ceiver, the communication with the common flock being

We cut off.

think that ingenious gentleman was deceived,

when he imagined (in his Sequel) that the eledlrical

fire came down the wire from the cieling to the gun-

barrel, thence to die fphere, and fo eledtrifed the machine

and

—

i6

Mr B. F R A N K L I N's

We and the man turning the wheel, &c.

fuppofe It was

driven off, and not brought on thro* that wire j and that the machine and man, &c. were eledtrifed minus j /. e. had ' lefs eleftrical fire in them than things in common.

As the veiiel is juft upon failing, I cannot give you fo

large an account of American Electricity as I intended : I

— We fliall only mention a few particulars more.

find gra-

nulated lead better to fill the phial with, than water, being

eafily warnied> and keeping warm and dry in damp air.

We fire fpirits with the wire of the phial.

We light

candies, juft blown out, by drawing a fpark among the

— We fmoke between the wire and fnufFers.

reprefent

lightning, by pafling the wire in the dark over a china

plate that has gilt flowers, or applying it to gilt frames of

— We looking-glafies, &c,

eleftrife a perfon twenty or

more times running, with a touch of the finger on the

wire, thus : He ftands on wax. Give him the eledlrifed
bottle in his hand. Touch the wire with your finger, and

then touch his hand or face ; there are fparks every

— We time.

encreafe the force of the eledlrical kifs vaftly,

A B thus : Let and ftand on wax > give one of them the

eled:rifed phial in hand ^ let the other take hold of the

wire ; there will be a fmall fpark ; but when their lips ap-

proach, they will be ftruck and fhock'd. The fame if

another gentleman and lady, C and JD, ftanding alfo on

A wax, and joining hands with and B, falute, or fhake

— We hands.

fufpend by fine filk thread a counterfeit fpi-

der, made of a fmall piece of burnt cork, with legs of lin-

nen

Letters (?;^ Electricity.

17

nen thread, and a grain or two of lead ftuck in him to give

him more weight. Upon the table, over v/hich he hangs>

we flick a wire upright as high as the phial and wire, two or three inches from the fpider ; then we animate

him by fetting the electrified phial at the fame diftance on

the other fide of him ; he will immediately fly to the wire of the phial, bend his legs in touching it, then fpring

off^, and fly to the wire in the table ; thence again to the wire of the phial, playing with his legs againfl: both in a

very entertaining manner, appearing perfeftly alive to per-

fons unacquainted. He will continue this motion an hour

—We or more in dry weather,

electrify, upon wax in the

dark, a book that has a double line of gold round upon the

covers, and then apply a knuckle to the gilding -, the fire

appears every where upon the gold like a flafli of light-

ning : not upon the leather, nor, if you touch the leather

We infliead of the gold.

rub our tubes with buckflcin,

and obferve always to keep the fame fide to the tube, and

never to fully the tube by handling ; thus they work rea-

dily and eafily, without the leafl: fatigue ; efpecially if kept

in tight paft:board cafes, lined with flannel, and fitting
— clofeto the tube.^ This I mention becaufe the European

papers, on Eleftricity, frequently fpeak of rubbing the

tube, as a fatiguing exercife. Our fpheres are fixed on

iron axes, which pafs through them. At one end of the

* Our tubes are made here of green glafs, 27 or 30 inches long, as big as can be grafped. Eledricity is fo much in vogue, that above one hun-
dred of them have been fold within thefe four months part.

D

axis

i8 Mr B. franklin's
axis there is a fmall handle, with which we turn the fphere like a common grindftone. This we find very commodious,
as the machine takes up but little room, is portable, and
may be enclofed in a tight box, when not in ufe. 'Tis true, the fphere does not turn fo fwift, as when the great wheel is ufed : but fwiftnefs we think of little importance, fince
a few turns will charge the phial, &c. fufficiently.

Jam^ &c»

B. FRANKLIN.

LET-

Letters on Electricity*

19

LETTER in.
FROM
Mr Benj- Franklin^ in Philadelphia^
to Mr Pe T E R Co L L I N s o N, F* R. S* London,

Farther Experi agents ^;^^ Observations
in ELECTRICITY,

5 7i?,

1748.

^ATpHERE § I.

will Idc the fame exploiion and fhock, if the electrified phial is held in one hand by the

hook, and the coating touch'd with the other, as when

held by the coating, and touch'd at the hook.

2. To take the charged phial fafely by the hook, and

not at the fame time diminifh its force, it muft firft be fet

down on an eledlric perfe.

3. The phial will be eleftriiied as ftrongly, if held by

the hook, and the coating apply'd to the globe or tube 5

as when held by the coating, and the hook apply'd.

D2

4. But

;;:
20 Mr B. franklin's /
4. But the dire5fion of the eledlrlcal fire being different in the charging, will alfo be different in the explofion.
The bottle charged thro' the hook, will be difcharged thro^
the hook ; the bottle charged thro' the coating, will-be difcharged thro' the coating, and not other ways •; for the fire mufl come out the fame way it went in.
5. To prove this ; take two bottles that were equally
charged thro' the hooks, one in each hand ; bring their hooks near each other, and no fpark or fhock will follow becaufe each hook is difpafed to give fire, and neither to
receive it. Set one of the bottles down on glafs, take it up by the hook, and apply its coating to the hook of the other
then there will be an explofion and fhock, and both bottles will be difcharged.
6. Vary the experiment, by charging two phials equally, one thro' the hook, the other thro' the coating : hold that by the coating which was charged thro' the hook -, and that by the hook which was charg'd thro' the coating : apply the hook of the firfl to the coating of the other, and
there will be no fliock or fpark. Set that down on glafs which you held by the hook, take it up by the coating,
and bring the two hooks together : a fpark and fliock will follow, and both phials be difcharged.
In this experiment the bottles are totally difcharged, or
the equilibrium v/ithin them reflored. Th& abcu/idiijg (xf
fire in one of the hooks (or rather in the internal furface of one bottle) being exadly equal to the ivanting of the other and therefore, as each bottle has in itfelf the abounding as
well

Letters on Electricity.

21

well as the wanting^ the wanting and abounding muft be
equal in each bottle. See §. 8, 9, lo, 1 1. But if a man
liolds in his hands two bottles, one fully eleftrify'd, the other not. at all, and brings their hooks together, he has but half a fhock, and the bottles will both remain half eledtriiied, the one being half difcharged, and the other
half charged.
7. Place two phials equally charged on a table at five or fix inches diftance. Let a cork-ball, fufpended by a filk thread, hang between them. If the phials were both
charged through their hooks, the cork, when it has been
attrafted and repell'd by the one, will not be attraded, but equally repelled by the other. But if the phials were charged, the one through the hook, and the other ^through the
coating, the ball, when it is repelled from one hook, will
be as ftrongly attracted by the other, and play vigoroufly between them, 'till both phials are nearly difcharged.
8. When we ufe the terms oi chargiiig and difcharging
the phial, 'tis in compliance with cuftom, and for want of
others more fuitable. Since we are of opinion, that there
is really no more ele6lrical fire in the phial after what is
called its charging^\}^2s\ before, nor lefs after its difcharging-^ excepting only the fmall fpark that might be given to, and taken from, the non-ele&ie matter, if feparated from

* To charge a bottle commodioufly through the coating, place it on a

glafs ftand ; form acommunication from the prime condudor to the coating,

When and another from the hook to the wall or floor.

it is charged, re-

move the latter communication before you rake hold of the bottle, other-

wife great part of the fire will efcape by it.

the

22 Mr B. F R ANKLIN's

the bottle, which fpark may not be equal to a five hun*
dredth part of what is called the explofion.

For if, on the explofion, the eleftrical fire came out of the bottle by one part, and did not enter in again by ano-*
ther ; then, if a man ftanding on wax, and holding the
bottle in one hand, takes the fpark by touching the wire

hook with the other, the bottle being thereby difcharged^
the man would be charged \ or whatever fire was loft by one, would be found in the other, fince there is no way

for its efcape : But the contrary is true.

9. Befides the phial will not fuff'er what is called a char-*

ging^ unlefs as much fire can go out of it one way, as is

A thrown in by another.

phial cannot be charged ftand-

ding on wax or glafs, or hanging on the prime condudlor,

unlefs a communication be form'd between its coating and

the floor.

10. But fufpend two or more phials on the prime con-

dudlor, one hanging to the tail of the other j and a wire from the laft to the floor, an equal number of turns of the wheel fliall charge them all equally, and every one as
much as one alone would have been. What is driven out

at the tail of the firft, ferving to charge the fecond ; what is driven out of the fecond charging the third ; and fo on* By this means a great number of bottles might be charged

with the fame labour, and equally high, with one alone,

were it not that every bottle receives new fire, and lofes

its old with fome reludlance, or rather gives fome fmall re-

fifl:ance to the charging, which in a number of bottles be-

comes

.

Letters on Electricity.

23

comes more equal to the charging power, and fo repels the fire back again on the globe, fooner than a fingle bottle would do.
1 1 When a bottle is charged in the common way, its
tnlide and outfide furfaces Hand ready, the one to give fire by the hook, the other to receive it by the coating ; the one is fiiU, and ready to throw out, the other empty and extremely hungry ; yet as the firfl: will not give out, unlefs the other can at the fame infl:ant receive in ; fo neither will the latter receive in, unlefs the firft can at the fame inftant
give out. When both can be done at once, 'tis done with
inconceivable quicknefs and violence. 12. So a ftrait fpring (tho' the comparifon does not a-
gree in every particular) when forcibly bent,mufl:,to reftore
itfelf, contraft that fide which in the bending was extended, and extend that which was contrafted ^ if either of thefe two operations be hindered, the other cannot be done. But the fpring is not faid to be charged with elafticity when
bent, and difcharg'd when unbent ^ its quantity of elafti-
city is always the fame.. 13. Glafs, in like manner, has, within its fubftance,
always the fame quantity of eleftrical fire, and that a very great quantity in proportion to the mafi of glafs, as fhallbe
ftiewn hereafter. 14. This quantity, proportioned to the glafs, it ftrongly
and obftinately retains, and will have neither more nor lefs, though it will fuffer a change to be made in its parts and
fituation j /. e. we may take away part of it from one
of

24-

Mr B. F R A N K L I N's

of the fides, provided we throw an equal quantity into
the other.
15. Yet when the fituation of the eleftrical fire is thus altered in the glafs ; when fome has been taken from one
fide, and fome added to the other, it will not be at reft or
in its natural ftate, till 'tis reftored to its original equality.-—
And this reftitution cannot be made through the fubftance
of the glafs, but muft be done by a non-eledtric communication formed without, from furface to furface.
16. Thus, the whole force of the bottle, and power of giving a fliock, is in the glass itself; the non-ele6brics in cont/aft with the two furfaces, ferving only to give and receive to and from the feveral parts of the glafs ; that is, to give on one lide, and take away from the other.
17. This was difcovered here in the following manner. Purpofmg to analyfe the eledlrified bottle, in order to find
wherein its ftrength lay, we placed it on glafs, and drew
out the cork and wire which for that purpofe had been
loofely put in. Then taking the bottle in one hand, and
bringing a finger of the other near its mouth, a ftrong fpark came from the water, and the fhock was as violent as if the wire had remained in it, which fhewed that the force did
not lie in the wire. Then to find if it refided in the water,
being crouded into and condenfed in it, as connfi'd by the
glafs, which had been our former opinion, we eleftrify'd
the bottle again, and placing it on glafs, drew out the wire
and cork as before ; then taking up the bottle we decanted
all its water into an empty bottle, which likewife flood on
glafs i

Letters on Elisctricity.

25

glafs ^ and taking up that other bottle, we expefted if the

force refided in the water, to find a fhock from it ; but

We there was none.

judged then, that it muft either be

loft in decanting, or remain in the firft bottle. The latter

W€ found to be true : for that bottle on trial gave the fhock,

though filled up as it flood with frefh uneledrified v/ater
— from a tea-pot. To find then, whether glafs had this

property merely as glafs, or whether the form contributed

any thing to it ; we took a pane of fafh-glafs, and laying

it on the ftand, placed a plate of lead on its upper furface ;

then eled:rify*d that plate, and bringing a finger to it, there

We was a fpark and fhock.

then took two plates of lead

of equal dimenfions, but lefs than the glafs by two inches

every way, and eleflrified the glafs between them, by

eledtrifying the uppermoft lead ; then feparated the

glafs from the lead, in doing which, what little fire

might be in the lead was taken out and the glafs be-

ing touched in the eledrified parts with a finger, af-

forded only very fmall pricking fparks, but a great

number of them might be taken from different places.

Then dexteroufly placing it again between the leaden

plates, and compleating a circle between the two furfaces,
— a violent fhock enfued. Which demonflrated the power

to refide in glafs as glafs, and that the non-eled:rics in con-

tadl ferved only, like the armature of a loadflone, to unite

the force of the feveral parts, and bring them at once to any

point defired : it being a property of a non-eledric, that

E

the

26

Mr B. F R A N K L I N's

the whole body inftantly receives or gives what eledtrical

fire is given to or taken from any one of its parts.
1 8. Upon this, we made what we call'd an ele5tricaU

battery^ confifting of eleven panes of large fafh-glafs, arm'd

with thin leaden plates pailed on each fide, placed verti-

cally, and fupported at two inches diflance on fiik cords^

with thick hooks of leaden wire, one from each fide,

flanding upright, diftant from each other, and convenient

communications of wire and chain, from the giving fide of one pane, to the receiving fide of the other ; that fo the Vv^hole might be charged together, and with the fame la-

bour as one fingle pane ; and another contrivance to bring

the giving fides, after charging, in contad; with one long

wire, and the receivers with another, which two long

wires would give the force of all the plates of glafs at once

through the body of any animal forming the circle with
them. The plates may alfo be difcharged feparately, or

any number together that is required. But this machine
is not much ufed, as not perfectly anfwering our intention

v/ith regard to the eafe of charging, for the reafon

We given § lo.

made alfo of large glafs panes, magical

pidlures, and felf-moving animated wheels, prefently to be

defcribed.

Mr 19. I perceive by the ingenious

Watforis lafl book,

lately received, that Dr Bevis had ufed, before we had,

panes of glafs to give a fhock j though, till that book came to hand, I thought to have communicated it to you as a
novelty. The excufe for mentioning it here, is;, that we

tried

Letters on Electricity.

27

tried the experiment differently, drew different confequen-

Mr ces from it, (for

Watfon ftill feems to think the fire

accumulated on the non-eleBric that is in contact with the
glafs, page 72) and, as far as we hitherto know, have car-

ried it farther.
20. The magical picture is made thus. Having a large

metzotinto with a frame and glafs, fuppofe of the King,

(God preferve him) take out the print, and cut a pan-

nel out of it, near two inches diilant from the frame all

round. If the cut is through the picture 'tis not the worfe.
With thin pafte or gum-water, fix the border that is cut off

on the infide of the glafs, prefTmg it fmdoth and clofe -,

then fill up the vacancy by gilding the glafs well with leaf

gold or brafs. Gild likewife the inner edge of the back of

the frame all round except the top part, and form a com-

munication between that gilding and the gilding behind

the glafs : then put in the board, and that fide is finifhed.

Turn up the glafs, and gild the fore fide exadlly over the

back gilding, and when it is dry, cover it by pafling on

the pannel of the picture that had been cut out, obferving

to bring the correfponding parts of the border and pidlure

together, by which the picture will appear of a piece as at
— firft, only part is behind the glafs, and part before. Hold

the picture horizonially by the top, and place a little
moveable gilt crown on the king s-head. If now the pic-

ture be moderately electrified, and another perfon take hold

of the frame with one hand, fo that his fingers touch its

infide gilding, and with the other hand endeavour to take

E2

oft

28 Mr B. FRANKLIN'S

off* the crown, he will receive a terrible blow, and fail In

the attempt. If the pidture were highly charged, the con-

fequence might perhaps be as fatal as that of high-treafon ;
for when the fpark is taken through a quire of paper laid

on the picture, by means of a wire communication, it makes

a fair hole through every Iheet, that is, through 48 leaves,

(though a quire of paper is thought good armour againft

the pufli of a fword or even againft a piftol bullet) and
the crack Is exceeding loud. The operator, who holds the
pidlure by the upper-end, where the infide of the frame

is not gilt, to prevent its falling, feels nothing of the ihock,

and may touch the face of the pidure without danger, which he pretends is a teft of his loyalty. —- If a ring

of perfons take the ftiock among them, the experiment

is icalled. The Confpirators,

On 21.

the principle, in § 7, that hooks of bottles, dif-

ferently charged, will attracft and repel differently, is made,

an eleilrical wheel, that turns with conliderable ftrength,
A fmall upright fhaft of wood paffes at right angles through

a thin round board, of about twelve inches diameter, and

turns on a fharp point of iron fixed in the lower end, while

a ftrong wire in the upper-end pafling thro* a fmall hole

in a thin brafs plate, keeps the fhaft truly vertical. About

thirty radii of equal length, made of faili glafs cut in nar-

row Itrips, iflue horizontally from the circumference of the

board, the ends moft diftant from the center being about
four inches apart. On the end of every one, a brafs thim-

ble is fixed* If now the wire of a bottle eleftrified in the common

Letters on Electricity. •

29

common way, be brought near the circumference of thii
wheel, it will attradl the neareft thimble, and fo put the wheel in motion ; that thimble, in paffing by, receives a fpark,. and thereby being eledtrified is repelled and fo driven forwards ; while a fecond being attracted, approaches the wire, receives a fpark, and is driven after the firft, and
fo on till the wheel has gone once round, when the thim-
bles before eledtrified approaching the wire, inftead of being
attrafted as they were at firft, are repelled, and the motion
— prefently ceafes. But if another bottle which had been
charged through the coating be placed near the fame wheel, its wire will attrad: the thimble repelled by the firft, and thereby double the force that carries the wheel round ; and not only taking out the fire that had been communicated to the thimbles by the firft bottle, but even robbing them of their natural quantity, inftead of being re-
pelled when they come again towards the firft bottle, they
are more ftrongly attradted, fo that the wheel mends its
pace, till it goes with great rapidity twelve or fifteen rounds in a minute, and with fueh ftrength, as that the weight of
one hundred Spanifo dollars with which we once loaded
— it, did not feem in the leaft to retard its motion. This is
called an eleftrical jack 5 and if a large fowl were fpitted on the upright fhaft, it would be carried round before a fire with a motion fit for roafting.
22. But this wheel, like thofe driven by wind, water, or weights, moves by a foreign force, to wit, that of the bot-
tles. The felf-moving wheel, though conftrufted on the
fiime

30

Mr B. F R A N K L I N.'s

fame principles, appears more furprifing. 'Tis made of a

thin round plate of window-glafs, feventeen inches diame-

ter, well gilt on both fides, all but two inches next the
edge. Two fmall hemifpheres of wood are then fixed

with cement to the middle of the upper and under fides,

centrally oppofite, and in each of them a thick ftrong wire

eight or ten inches long, which together make the axis of

the wheel. It turns horizontally on a point at the lower

end of its Axis, which refts on a bit of brafs cemented

within a glafs falt-celler. The upper end of its axis paffes

thro' a hole in a thin brafs plate cemented to a long ftrong

piece of glafs, which keeps it fix or eight inches diftant

from any non-eledric, and has a fmall ball of wax or me-

tal on its top to keep in the fire. In a circle on the table

which fupports the wheel, are fixed twelve fmall pillars of

glafs, at about four inches diftance, with a thimble on the
top of each. On the edge of the wheel is a fmall leaden

bullet communicating by a wire with the gilding of the up-

per furface of the wheel ; and about fix inches from it is

another bullet communicating in like manner with the
tmder furface. When the vfheel is to be charged by the

upper furface, a communication mufl: be made from the

When under furface to the table.

it is well charged it be-

gins to move ', the bullet neareft to a pillar moves towards

the thimble on that pillar, and pafling by ele£trifies it and

then puflies itfelf from it ^ the fucceeding bullet, which communicates with the other furface of the glafs, more

llrongly attrads that thimble on account of its being be-

fore

Letters on Electricity.

31

fore eledrified by the other bullet 3 and thus the v/heel encreafes its motion till it comes to fuch a height as that the reiiftance of the air regulates it. It will go half an hour, and make one minute with another twenty turns in a minute, which is fix hundred turns in the whole ; the bullet of the upper furface giving in each turn twelve fparks, to the thimbles, which make feven thoufand two hundred fparks 5 and the bullet of the under furface receiving
as many from the thimbles 3 thofe bullets moving in the
— time near two thoufand five hundred feet. The thim-
bles are well fixed, and in fo exad: a circle, that the bul-
lets may pafs within a very fmall diftance of each of
— them. If inftead of two bullets you put eight, four com-
municating with the upper fiirface, and four with the under furface, placed alternately ; which eight, at about fix inches diftance, compleats the circumference, the force and fwiftnefs will be greatly increafed, the wheel making fifty turns in a minute 3 but then it will not continue moving fo
— long. Thefe wheels may be applied, perhaps, to the
ringing of chimes, and moving of light-made Orreries.
A 23. fmall wire bent circularly with a loop at each
end \ let one end reft againft the under furface of the wheel, and bring the other end near the upper furface, it will give a terrible crack, and the force will be
difcharged.
24. Every fparkinthat manner drawn from the furface of the wheel, makes a round hole in the gilding, tearing off a part of it in coming cut 3 which fliews that the fire
is

32

Mr B. F R A N K L I N's

is not accumulated on the gilding, but is in the glafs

itfelf.
25. The gilding being varnifh*d over with turpentine
varnifh, the varnifh tho* dry and hard, is burnt by the fpark

drawn thro' it, and gives a ftrong fmell and vifible fmoke.
And when the fpark is drawn through paper, all round the

hole made by it, the paper will be blacked by the fmoke,

which fometimes penetrates feveral of the leaves. Part

Qf the gilding torn off, is alfo found forcibly driven into

the hole made in the paper by the ftroke.

26. 'Tis amazing to obferve in how fmall a portion of

A glafs a great eleftrical force may lie.

thin glafs bubble,

about an inch diameter, weighing only fix grains, being

half-filled with water, partly gilt on the outfide, and fur-
nifli'd with a wire hook, gives, when eledrified, as great a ftiock as a man can well bear. As the glafs is thickefl:

near the orifice, I fuppofe the lower half, which being gilt

was electrified, and gave the fhock, did not exceed two
grains ; for it appeared, when broke, much thinner than
— the upper half. If one of thefe thin bottles be eleftrified

by the coating, and the fpark taken out thro' the gilding,

it will break the glafs inwards at the fame time that it

breaks the gilding outwards.

27. And allowing (for the reafons before given, § 8, 9,
10,) that there is no more eleftrical fire in a bottle after
charging, than before, how great muft be the quantity in

this fmall portion of glafs ! It feems as if it were of its very fubftance and efience. Perhaps if that due quantity of

eled;rical

Letters on Electricity*

33

electrical fire fo obftinately retained by glafs, could be

— feparated from it, it would no longer be glafs j It might
lofe its tranfparency, or its brittlenefs, or its elafciclty.
Experiments may poffibly be invented hereafter, to dif-

cover this.

We 27.

Mr are furprized at the account given in

Wat-

Jon % book, of a fhock communicated through a great fpacc

of dry ground, and fufped: there muft be fome metaline

quality in the gravel of that ground > having found that
fimple dry earth, rammed in a glafs tube, open at both

ends, and a v/ire hook inferted in the earth at each end, the earth and wires making part of a circle, would not con-
dud the leaft perceptible fhock, and indeed when one

wire was eleftrify'd, the other hardly fhowed any ligns of
— its being in conneaion with it. Even a thoroughly

wet pack-thread fometimes fails of conducing a fhock^

A tho' it otherwife condufts eleftricity very v/ell.

dry

cake of ice, or an icicle held between two in a circle, like-

wife prevents the fhock ; which one would not exped:, as
— water conduces it fo perfeftly well. Gilding on a new

book, though at firft it conduits the lliock extremely well,

yet fails after ten or a dozen experiments, though it ap-
pears otherwife in all refpeds the fame, which we cannot

account for.

28. There is one experiment more which furprizes us,

and is not hitherto fatisfaftorily accounted for ; it is this.
Place an iron fliot on a glafs ftand, and let a ball of damp

cork, fufpended by a filk thread, hang in contact with the

F

lliot

:

34

Mr B. F R A N KL 1 N's

fhot. Take a bottle in each hand, one that is eledtrify'd

through the hook, the other through the coating : Apply

the giving wire to the {hot, which will eleftrify it pofitive^

/);, and the cork fhall be repelled : Then apply the requir-

ing

wire,

which

will

take

out

the

fpark

given

by

the

other ^

when the cork will return to the fhot : Apply the fame

again, and take out another fpark, fo will the iliot be elec-

trify'd negatively , and the cork in that cafe fhall be repel-
led equally as before. Then apply the giving wire to the

fhot, and give the fpark it wanted, fo will the cork return

Give it another, which will be an addition to its natural
quantity, fo will the cork be repelled again : And fo may

the experiment be repeated as long as there is any charge

in the bottles. Which fhews that bodies having lefs thaa

the common quantity of Eleftricity, repel each other, as

well as thofe that have more.
Chagrined a little that we have hitherto been able to

produce nothing in this way of ufe to mankind ; and the hot weather coming on, when electrical experiments are

not fo agreeable, 'tis propofed to put an end to them for

this feafon, fomewhat humoroufly, in a party of pleafur^e,

on the banks of SkuylkilL^ Spirits, at the fame time, are

to be fired by a fpark fent from fide to fide through the

river, without any other condudlor than the water ; an
experiment which we fome time fince performed, to the

* The river that wafhes one fide of Philadelphia^ as the Delaware does the other ; both are ornamented with the fummer habitations, of the citi-
zens, and the agreeable manfions of the principal people of this colony.

amazement

Letters on Electricity*

ZS

A amazement of many.

turkey is to be killed for our

dinner by the eleBricalJJoock^ and roafted by the eleclrical

jack^ before a fire kindled by the elettrified bottle j when the

healths of all the famous eleftricians in England^ Holland^

France^ and Germmiy^ are to be drank in "^ ele5irified bumperSy under the difcharge of guns from the elcBrical

battery.

An eledlrified bumper, is a fmall thin glafs tumbler, near filled with
wine, and eledlrified as the bottle. This when brought to the lips gives a fhock, if the party be clofe ftiaved, and does not breathe on the liquor.

^pril 29*, 1749,

F2

LET*

ANKL 36

Mr B. F R

IN's

LETTER IV.

CONTAINING

OBSERVATIONS ^;^^ SUPPOSITIONS,

Hy towards for^ning a new

p o t h e s i s, for ex-

•plaining the feveral Phenomena of Thun-

der-Gusts,*

SIR,
On-ele(!tric bodies, that have eledric
fire thrown into them, will retain it 'till other non-eled:rics, that have lefs, approach 5 and then 'tis communicated by a fnap, and becomes equally divided. 2. Electrical fire loves water, is flrongly attracted by it, and they can fubfift together.
3. Air is an eleftric /^r^^, and when dry will not con-
dud: the eleftrical fire j it will neither receive it, nor give
* Thunder-gufls are fudden llorms of thunder and lightning, which
are frequently of foort duration, but fometiipes produce mifchievous
cfFeds. it

Letters on Electricity.

37

it to other bodies ; otherwife no body farrounded by air could be eleftriiied politively and negatively : for fhould it be attempted politively, the air v^ould immediately take

away the overplus -, or negatively, the air v/ould fupply

what was wanting.

4. Water being eleftriiied, the vapours arifing from it wall be equally eleftrified ; and floating in the air^ in the form of clouds, or otherwife, will retain that quantity of

eledirical fire, till they meet with other clouds or bodies
not fo much eledlrified, and then will communicate as be-

forementioned.

5. Every particle of matter eleclriiied is repelled by
every other particle equally eledtrified. Thus the ftream of a fountain, naturally denfe and continual, when eledlri-

fied, will feparate and fpread in the form of a brufh, every drop endeavouring to recede from every other drop. But

on taking out the eleftrical fire, they clofe again.
6. Water being ftrongly eledirified (as well as when heated by common fire) rifes in vapours more copioufly y the attradlion of cohefion among its particles being greatly
weakened, by the oppofite power of repulfion introduced
with the eledlrical fire ; and when any particle is by any
means difengaged, 'tis immediately repelled, and fo flies

into the air.

A 7. Particles happening to be fituated as

and S, are

more eafily difengaged than C and Z), as each is held by

D contadt with three only^ whereas C and

are each in

contadl with nine. When the furface of water has the

Icall

3^

Mr B. F R A N K L I N 's

leaft motion, particles are continually puflied into the
Situation reprefented by Fig. 6.

8. Fridlion between a non-eleftric and an dedcnc per fe^ ' will produce electrical fire ; not by creating, but coUe&ing

it : for it is equally difFufed in our walls, floors, earth, and
^he whole mafs of common matter. Thus the whirling

glafs globe, during its friftion againft the cufhion, draws

fire from the cufliion, the cufhion is fupplied from the frame of the machine, that from the floor on which it

ftands. Cut off the communication by thick glafs or wax

placed under the cufhion, and no fire can be produced^ be-

caufe it cannot be colleBed,

9. The Ocean is a compound of water, a non-eledtric,

and fait an €i^Q(x\Q per fe,

When 10.

there is a friftion among the parts near its

furface, the eledtrical fire is colle6ted from the parts below.

It is then plainly vifible in the night 5 it appears at the
ilern and in the wake of every failing vefTel 3 every dafh

of an oar fhows it, and every furffand fpray : in ftorms the
— whole fea feems on fire. The detached particles of water

then repelled from the eledirified furface, continually car-

ry off the fire as it is colledled 3 they rile, and form clouds,

and thofe clouds are highly eleftrified, and retain the fire

'till they have an opportunity of communicating it.

11. The particles of water rifing in vapours, attach

themfelves to particles of air.
1 2. The particles of air are faid to be hard, round, fepa-

rate and diflant from each other ; every particle flrongly

repelling

Letters on Electricity.

39

repelling every other particle, whereby they recede from
each other, as far as common gravity will permit. 13. The fpace between any three particles equally re-
pelling each other, will be an equilateral triangle.

14. In air compreffedy thefe triangles are fmaller 5 in

rarified Air they are larger..

15. Common fire joined with air, increafes the repul-

fipn, enlarges the triangles, and thereby makes the air fpe-

cifically lighter,

Such
.

Air

among

denfer

air,

will

rife.

Common 16.

fire, as well as electrical fire gives repul-

fion to the particles of water, and deftroys their attradlion
of cohefion ; hence common fire, as well as electrical fire,

aflifts in raifing vapours.
17. Particles of water, having no fire in them, mutually attradt each other. Three particles of water then being

attached to the three particles of a triangle of air, would by

their mutual attraction operating againfi: the air's repulfion, fliorten the fides and leflen the triangle, whereby that
portion of air being made denfer, would fink to the earth

with its water, and not rife to contribute to the formation

of a cloud.

18. But if every particle of water attaching itfelf to air,
brings with it a particle of common fire, the repulfion of

the air being aflifted and ftrengthened by the fire, more

than obftruflied by the mutual attradion of the particles of

water, the triangle dilates, and that portion of air becom-

ing rarer and fpecifically lighter rifes.
19 If the particles of water bring ^eQrical fire when
they

40

Mr B. F R A N KL IN's

they attach themfelves to air, the repulfion between the particles of water eleftrified, joins with the natural repul-

fion of the air, to force its particles to a greater diftance,
whereby the triangles are dilated, and the air rifes, carrying -Up with it the water.
20. If the particles of water bring with them portions
ei both forts of fire, the repullions of the particles of air is
ftill more ftrengthened and increafed, and the triangles

farther enlarged.
21. One particle of air may be furrounded by twelve

particles of water of equal fize with itfelf, all in contact

with it ; and by more added to thofe.

22. Particles of air thus loaded would be drawn nearer

together by the mutual attraction of the particles of water,

common did not the fire,

or electrical, affift their re-

pullion.
23. If air thus loaded be compreffed by adverfe v/inds, or by being driven againfl: mountains, &c. or condenfed by takings-way the fire that affifted it in expanding ; the triangles contrail, the air with its water will defcend as a
dew 3 or, if the water furrounding one particle of air comes
in contafi: with the water furrounding another, they coa-
lefce and form a drop, and we have rain. 24. The fun fupplies (or feems to fupply) common fire
to all vapours, whether raifed from earth or fea.
25. Thofe vapours which have both common and elec-
trical fire in them, are better fupported, than thofe which
have only common fire in them. For when vapours rife

into

Letters on Electricity.

41

>

into the coldeft region above the earth, the cold v/ill not

diminifh the eleftrical iire, if it doth the common.

26. Hence clouds formed by vapours raifed from frefh

waters within land, from growing vegetables, moifl earth,

&c. more fpeedily and ealily depofite their v/ater, having

but little eledtrical fire to repel and keep the particles fepa-

rate. So that the greateft part of the water raifed from the

land is let fall on the land again \ and winds blowing from

the land to the fea are dry ; there being little ufe for rain

on the fea, and to rob the land of its moifture, in order to

rain on the fea, would not appear reafonable.

27. But clouds formed by vapours raifed from the fea,

having both fires, and particularly a great quantity of the

eledrical, fupport their water ftrongly, raife it high, and

being moved by winds may bring it over the middle of

the broadeft continent from the middle of the wideft ocean.

How 28.

thefe ocean clouds, fo ftrongly fupporting

their water, arc made to depofite it on the land where 'tis

wanted, is next to be confidered.

29. If they are driven by winds againft mountains,

thofe mountains being lefs eleftrified attraft them, and on

contact take away their eledlrical fire (and being cold, the

common fire alfo ; ) hence the particles clofe towards the
mountains and towards each other. If the air was not

much loaded, it only falls in dews on the mountain tops

and fides, forms fprings, and defcends to the vales in rivu-

lets, which united make larger fl:reams and rivers. If

much loaded, the electrical fire is at once taken from the

G

whole

42

Mr. B. F R A N K L I N's

whole cloud ^ and, in leaving it, flaflies brightly and cracks loudly ; the particles inftantly coalefcing for want of that fire, and falling in a heavy fliower.
30. When a ridge of mountains thus dams the clouds,'
and draws the eledlrical fire from the cloud firft approach-
ing it 5 that which next follows, when it comes near the firft cloud, now deprived of its fire, flafhes into it, and begins to depofite its own water j the firft cloud again flafhing
into the mountains ; the third approaching cloud, and all the fucceeding ones, adling in the fame manner as far
back as they extend, which may be over many hundred
miles of country.
31. Hence the continual ftorms of rain, thunder, and lightning on the eaft-fide of the Andes^ which running
north and fouth, and being vaftly high, intercept all the
clouds brought againft them from the Atlantic ocean by the trade winds, and oblige them to depofite their waters,
by which the vaft rivers Amazons^ ha Plata^ and OroonoM
are formed, which return the water into the fame fea, after
having fertilized a country of very great extent. 32. If a country be plain, having no mountains to inter-
cept the eledrified clouds, yet is it not without means to
make them depofite their water. For if an electrified
cloud coming from the fea, meets in the air a cloud raifed from the land, and therefore not eleftrified \ the firft will flalh its fire into the latter, and thereby both clouds fliall be made fuddenly to depofite waten
33. The eledlrified particles of the firft cloud clofe when they lofe their fire \ the particles of the other cloud
clofe

Letters en lELUcrKicrrv.

43

cTofe in receiving it : in both, they have thereby an opoortu-
— nity of coalefcing into drops. The concuffion or jerk given
to the air, contributes alfo to fliake down the water, not
only from thofe tvv^o clouds but from others near them.
Hence the fudden fall of rain immediately after flaflies of

lightning.
- 34. To fhew this by an eafy experiment. Take two
round pieces of pafteboard two inches diameter ; from the center and circumference of each of them fufpend by

fine filk threads eighteen inches long, feven fmall balls of

wood, or (even peas equal in bignefs 5 fo will the balls appending to each pafteboard, form equal equilateral trian-

gles, one ball being in the centejr, and fix at equal diftances

from that, and from each other ; and thus they reprefent particles of air. Dip both fets in water, and fome cohering

to each ball they will reprefent air loaded. Dexteroufly

eledtrify one fet, and its balls will repel each other to a greater diftance, enlarging the triangles. Could the water
fupported by the feven balls come into contad:, it would form a drop or drops fo heavy as to break the cohe-
— fion it had with the balls, and fo fall. Let the two fets
then reprefent two clouds, the one a fea cloud eled:rified, the other a land cloud. Bring them within the fphere of

attradion, and they will draw towards each other,

and you will fee the feparated balls clofe thus ; the firft elcdbrified ball that comes near an uneledrified ball by

attradion joins it, and gives it fire ; inftantly they fepa-

rate, and each flies to another ball of its own party, one to

G2

give

44 Mr B. franklin's

give, the other to receive fire ^ and fo it proceeds through both fets, but fo quick as to be in a manner inftantaneous. In he coUifion they ihake off and drop their water, which

reprefents rain.
35. Thus when fea and land clouds would pafs at too
great a diftance for the flafh, they are attracted towards

each other till within that diftance > for the fphere of eledtrical attraftion is far beyond the diftance of flafhing. .
36. When a great number of clouds from the fea meet
a number of clouds raifed from the land, the eleftrical

flafhes appear to ftrike in different parts 5 and as the clouds are joftled and mixed by the winds, or brought

near by the eleftrical attradtion, they continue to give and

receive flafh after flafh, till the eleftrical fire is equally

diffufed.

When 37.

the gun-barrel (in eleftrlcal experiments)

has but little eleftrieal fire in it, you muft approach it very

near with your knuckle, before you can draw a fpark.

Give it more fire, and it will give a fpark at a greater dif-

Two tance.

gun-barrels united, and as highly eledlrified,

will give a fpark at a ftill greater diftance. But if two

gun-barrels eleftrified will ftrike at two inches diftance,

and make a loud fnap, to what a great diftance may

10,000 acres of eleftrified cloud ftrike and give its fire,
and how loud muft be that crack ! 38. It is a common thing to fee clouds at different
heights paffing different ways, which fhews different cur-

rents of air, one under the other. As the air between the

tropics

Letters on Electricity.

45

tropics is rarified by the fun, it rifes, the denfer northern
and fouthern air preffing into its place. The air fo rari-

fied and forced up, palTes northward and fouthward, and

muft defcend in the polar regions, if it has no opportunity
before, that the circulation may be carried on.

39. As currents of air, with the clouds therein, pafs dif-
ferent ways, 'tis eafy to conceive how the clouds, paffing over each other, may attradt each other, and fo come near enough for the eleftrical ftroke. And alfo how eledlrical clouds may be carried within land very far from the fea,

before they have an opportunity to ftrike.
40. When the air, with its vapours raifed from the o-

cean between the tropics, comes to defcend in the polar

regions, and to be in contact with the vapours arifing

there, the eleftrical fire they brought begins to be com-

municated, and is feen in clear nights, being firft vifible

where 'tis firft in motion, that is, where the contad; be-

gins, or in the moft northern part 5 from thence the ftreams of light feem to fhoot foutherly, even up to the

zenith of northern countries. But tho' the light feems to

fhoot from the north foutherly, the progrefs of the fire is

really from the fouth northerly, its motion beginning in

the north being the reafon that 'tis there firft feen.
For the eleftrical fire is never vifible but when in mo-

tion, and leaping from body to body, or from particle to

When particle thro' the air.

it pafles thro' denfe bodies,

When ''tis unfeen.

a wire makes part of the circle, in the

explofion of the eledrical phial, the fire^ though in great quantm%

46 Mr B. FR ANKLIN^s

quantity, paffes in the wire inviUbly : but in paffing along* a chain, it becomes vifibie as it leaps from link to link. In paffing along leaf-gilding 'tis viUble : for the leaf-gold is full of pores ; hold a leaf to the light and it appears like a' net ; and the fire is fetn in its leaping over the vacancies,—
And as when a long canal filled with ftill water is open-
ed at one end, in order to be difcharged, the motion of the water begins firft near the opened end^ and proceeds towards the clofe end, tho' the water itfelf moves from the

clofe towards the opened end : fo the eledlrical fire difcharged into the polar regions, perhaps from, a thoufand leagues length of vaporized air, appears firft where 'tis firft in motion, /. e, in the moft northern part, and the appearance proceeds fouthward, tho' the fire really moves northward. This is fuppofed to account for the Auj'-ora Bg-^

realis,

When 41.

there is great heat on the land, in a particu-

lar region (the fan having fhone on it perhaps feveral

days, while the furrounding countries have been fcreen'd

by clouds) the lower air is rarified and rifes, the cooler

denfer air above defcends ; the clouds in that air meet

from all fides, and join over the heated place -, and if fome

are eled-rified, others not, lightning and thunder fucceed,

and fhowers fall. Hence thunder-gufts after heats, and

cool air after gufts ; the water and the clouds that bring

it, coming from a higher and therefore a cooler region.
42. An eledlrical fpark, drawn from an irregular body

at fome diftance is fcarce ever ftrait, but fhows crookr

cd

;

/Letters on Electricity.

47

ed and waving In the air. So do the flafhes of lightning

th-e clouds being very irregular bodies.

43. As eleftrified clouds pafs over a country, high
hills and high trees, lofty towers, fpires, marts of fhips,
chimneys, G?r. as fo many prominencies and points, draw

the eledrical fire, and the whole cloud difcharges there.

44. Dangerous, therefore, is it to take fhelter under a tree during a thunder-guft. It has been fatal to many,
both men and beafts.

45. It is fafer to be in the open field for another reafon.
When the clothes are wet, if a flafh in its way to the

ground fhould ftrike your head, it will run in the water

over the furface of your body -, whereas, if your clothes

were dry, it would go thro' the body.

, Hence a wet rat cannot be killed by the exploding e-

leSrical bottle, when a dry rat may.

Common 46.

fire is in all bodies, more or lefs, as well

as eledtrical fire. Perhaps they may be different modifi-

cations of the fame element ; or they may be different ele-

ments. The latter is by fome fufpedled.

47. If they are different things, yet they may and do

fubfifl together in the fame body.

When 48.

electrical fire flrikes thro' a body, it adls

upon the common fire contained in it, and puts that fire

in motion ; and if there be a fufficient quantity of each

kind of fire, the body will be inflamed.
49. When the quantity of common fire in the body is
fmall, the quantity of the electrical fire (or the eleftrical

ftroke)

ANKL 48

Mr B. F R

IN's

ftroke) fhould be greater : if the quantity of common fire
be great, lefs electrical fire fuffices to produce the effedt.
50. Thus fpirits muft be heated before we can fire them by the eledrical fpark. If they are much heated a fmall
fpark will do ; if not, the fpark muft be greater.
5 1 . Till lately we could only fire warm vapours ; but now we can burn hard dry rofin. And when we can procure greater eleftrical fparks, we may be able to fire not
only unw^arm'd fpirits, as lightning doss, but even wood,
by giving fufficient agitation to the common fire contained in it, as friilion we know will do.
52. Sulphureous and inflammable vapours arifing from the earth, are eafily kindled by lightning. Befides what arife from the earth, fuch vapours are fent out by ftacks of moift hay, corn, or other vegetables, which heat and reek.
Wood rotting in old trees or buildings does the fame. Such
are therefore eafily and often fired. 53. Metals are often melted by lightning, tho* perhaps
not from heat in the lightning, nor altogether from agi-
— tated fire in the metals. For as whatever body can infi-
nuate itfelf between the particles of metal, and overcome the attraftion by which they cohere (as fundry menftrua
can) will make the folid become a fluid, as well as fire,
yet without heating it : fo the eledlrical fire, or lightning, creating a violent repulfion between the particles of the metal it paflfes thro*, the metal is fufed.
54. If you would, by a violent fire, melt off the end of a nail, which is half driven into a door, the heat given the
whole

Letters on Electricity.

49

whole nail before a part would melt, muft burn the board
it flicks in. And the melted part would burn the floor it
dropped on. But if a fword can be melted in the fcab-
bard, and money in a man's pocket, by lightning, without
burning either, it muft be a cold fufion.
t^j^. Lightning rends fome bodies. The eleflirical fpark
will ftrike a hole thro' a quire of ftrong paper. 56. If the fource of lightning, afligned in this paper, be
the true one^ there ihould be little thunder heard at fea
far from land. And accordingly fome old fea-captains, of
whom enquiry has been made, do affirm, that the fadt a-
grees perfectly with the hypothefis ; for that, in croffing the great ocean, they feldom meet with thunder till they
come into foundings ; and that the iflands far from the continent have very little of it. And a curious obferver,
who lived 1 3 years at Bermudas^ fays, there was lefs thun-
der there in that whole time than he has fometimes heard in a month at Carolina.

H

ADDITI-

ADDITIONAL PAPERS.

TO

Mr. Peter Collin son, F. R. S. London.

SIR,

Philadelphia, J&Iy 29, 175a

AS you firft put us on electrical experiments, by fending to our library company a tube^

with direftions how to ufe it ; and as our

honourable proprietary enabled us to carry thofe experi--

ments to a greater height, by his generous prefent of a

compleat eledrical apparatus ; 'tis fit that both ftiould
know from time to time what progrefs we make. It
Was in this view I wrote and fent you my former papers

on this fubjeft, defiring, that as I had not the honour of

a dired correfpondence with that bountiful benefador to
our library, they might be communicated to him through

your hands. In the fame view I write, and fend you this

additional paper. If it happens to bring you nothing
new (which may well be, confidering the number of in-

genious men in Europe^ continually engaged in the fame

refearches) at leaft it will fhow, that the inftruments,

put into our hands, are not negledled ^ and, that if no valuable difcoveries are made by us, whatever the caufe.
may be, it is not want of induftry and application.

I am^ Sir^

Tour much obliged

Humble Servant^
B. FRANKLIN,

Lettters on Electricity,

51

OPINIONS and CONJECTURES,

Concerning the Properties and EffeSis of the e-

leSlrical Matter^ arijing from Experiments

andObfervationSy made in Fhiladclphiay ly^g^

T'^HE § I. >"

eledlrical matter confifts of particles extreamly fubtile, fince it can permeate

common matter, even the denfeft metals,

with fuch eafe and freedom, as not to receive any percep-

trble rcliftance.
2. If any one fhould doubt, v^hether the eleftrical mat^ ter pafles thro* the fubftance of bodies, or only over and along their furfaces, a fhock from an eleftrified large
glafs jar, taken thro' his own body, will probably con-

vince him*
3. Eledrlcal matter differs from common matter in
this, that the parts of the latter mutually attradl, thofe of
the former mutually repel, each other. Hence the ap-

pearing divergency in a ftream of eledrified effluvia.

4. But tho* the particles of eled:rical matter do repel each other, they are ftrongly attracted by all other matter. *

^ See the ingenious eflaysoncledlridty in the Tranfadions, by 'Mr Ellkror.

H2

5. From

S2 MrB. FRANKLIN'S

5. From thefe three things, the extreme fubtilty of the
' electrical matter, the mutual repullion of its parts, and the
ftrong attradion between them and other matter, arife this eifed, that when a quantity of eledrical matter, is ap-
plied to a mafs of common matter, of any bignefs or length

within our obfervation (which has not already got its

quantity) it is immediately and equally diffuled through

the whole.

'

6. Thus common matter is a kind of fpunge to the eledrical fluid. And as a fpunge would receive no wa-
ter, if the parts of water were not fmaller than the pores

of the fpunge y and even then but flowly, if there were

not a mutual attradion between thofe parts and the parts

of the fpunge 5 and would flill imbibe it fafler, if the mutual attraction among the parts of the water did not

impede, fome force being required to feparate them y and fafteft, if, inftead of attraftion, there were a mutual repul-

iion among thofe parts, which would adl in conjunction

with the attracSlion of the fpunge. So is the cafe between
the electrical and common matter.. 7. But in common matter there Is (generally) as much

of the electrical, as it will contain within its fubftance. If

more is added, it lies without upon the furface, and forms
what we call an electrical atmofphere: and then the body

is faid to be elec^lrified.
8. 'Tis fuppofed, that all kinds of common matter do

not attract and retain the electrical, with equal ftrength and
force 5 for reafons to be given hereafter. And that thofe

called

Letters on Electricity.

^i^

called eledlrics />^r 7^, as glafs, &c. attraft and retain it

ftrongeft, and contain the greateft quantity.

We 9.

know that the elecflrical fluid is in common

matter, becaufe we can pump it out by the globe or tube.

We know that common matter has near as much as it can

contain, becaufe, when we add a little more to any pro-

tion of it, the additional quantity does not enter, but forms
an eleftrical atmofphere. And we know that common

matter has not (generally) more than it can contain, other-

wife all loofe portions of it would repel each other, as

they conftantly do when they ha,ve ele&ic atmofpheres.

i.a. The beneficial ufes of this eleftrical fluid in the

creation, we are not yet well acquainted with, though

doubtlefs fuch there are, and thofe very confiderable ; but

we may fee fome pernicious confequences, that would at-

tend a much greater proportion of it. For had this globe

we live on as much of it in proportion, as we can give to a

globe of iron, wood, or the like, the particles of duft and

other light matters that get loofe from it,- would, by virtue

of their feparate eleftrical atmofpheres, not only repel each

other, but be repelled from the earth, and not eafily be brought to unite with it again ; whence our air would continually be. more and more clogged with foreign matter, and grow unfit for refpiration. This affords another occafion of adoring that wifdom which has- made all things by weight and meafure !
II. If a piece of common matter be fuppofed intirely

jJee-from electrical matter, and a fingle particle of the

latter

54

Mr B. F R A N K L I N's

latter be brought nigh, 'twill be attrafted and enter the

body, and take place in the center, or where the attrac-

tion is every way equal. If more particles enter, they

take their places where the balance is equal between the

attraftion of the common matter and their own mutual

repulfion. 'Tis fuppofed they form triangles, whofe fides

fhorten as their number increafes ; 'till the common mat-

ter has drawn in fo many, that its whole power of com-

preffing thofe triangles by attradlion, is equal to their whole

power of expanding themfelves by repulfion ; and then

will fuch piece of matter receive no more.

When 12.

part of this natural proportion of eleftrical

fluid, is taken out of a piece of common matter, the trian-

gles formed by the remainder, are fuppofed to widen by

the mutual repulfion of the parts, until they occupy the

whole piece.

When 13.

the quantity of eledlrical fluid taken from a

piece of common matter is refl:ored again, it enters, the

expanded triangles being again compreflTed till there is

room for the whole.
14. To explain this: take two apples, or two balls of wood or other matter, each having its own natural quantity

of the eleftrical fluid. Sufpend them by filk lines from the

ceiling. Apply the wire of a well-charged vial, held in
A your hand, to one of them ( j Fig. 7. and it will receive
from the wire a quantity of the eleftrical fluid ; but will
not imbibe it, being already full. The fluid therefore will

flow round its furface, and form an eleftrical atmofphere.

Bring

Letters on Electricity*

55

A Bring into contad: with B, and half the eledrical fluid

is communicated, fo that each has now an elecSrical at-

mofphere, and therefore they repel each other. Take

away thefe atmofpheres by touching the balls, and leave

them in their natural ftate : then, having fixed a flick of

fealing wax to the middle of the vial to hold it by, apply

the wire to A, at the fame time the coating touches B.

Thus will a quantity of the eleftrical fluid be drawn out

of B, and thrown on A. So that A will have a redun-

dance of this fluid, which forms an atmofphere round it,

Now and B an exa£lly equal deficiency.

bring thefe

balls again into contad:, and the eleftrical atmofphere
A will not be divided between and B, into two fmaller

atmofpheres as before ; for B will drink up the whole at-
mofphere of A/ and both will be found again in their na-

tural flate.
1 5. The form of the eleftrlcal atmofphere is that of the body it furrounds. This fhape may be rendered
vifible in a flill air, by raifing a fmoke from dry rofin, dropt into a hot tea-fpoon under the eledlrifed body, which will be attracted and fpread itfelf equaly on all
fides, covering and concealing the body. And this form
it takes, becaufe it is attradled by all parts of the furface of
the body, tho' it cannot enter the fubftance already replete.
Without this attraflion it w^ould not remain round the bo-
dy, but diflipate in the air.
16. The atmofphere of electrical particles furrounding
an eledlrified fph^ere, is not more difpofed to leave it or more

56 Mr B. FRANKLIN'S

more eafily drawn off from any one part of the fphere than from another, becaufe it is equally attraded by every part. But that is not the cafe with bodies of any other figure. From a cube it is more eafily drawn at the corners than at the plane fides, and fo from the angles of a body of any other form, and ftill moft eafily from the angle that is nioft acute. Thus if a body fhaped as A, B,'C, D, E, in Fig. 8,
be electrified, or have an eledrical atmofphere com^muni-
cated to it, and we confider every fide as a bafe on which
the particles refl: and by which they are attraded, one
A m^ay fee, by imagining a line from to F, and another
from E to G, that the portion of the atmofphere included
in F, A, E, G, has the line A, E, for its bafis. So the portion of atmofphere included in H, A, B^ I, has the line
A, B, for its bafis. And likewife the portion inclu-

ded in K, B, C, L, has B, C, to reft on ; and fo

Now on the other fide of the figure.

if you would

draw off this atmofphere with any blunt fmooth body,

and approach the middle of the fide A, B, you muft come

very near before the force of your attrader exceeds the

force or power with which that fide holds its atmofphere.

But there is a fmall portion between I,B,K, that has lefs of

the furfaceto reft on, and to be attraded by, than the neigh-

bouring portions, while at the fame time there is a mutual

repulfion between its particles and the particles ofthofe por-

tions, therefore here you can get it with more eafe or at a

greater diftaace. Between F, A, H, there is a larger por-

tion that has yet a lefs furface to reft on and to attrad it^

'

Lettters ^/^Electricity.

57

here therefore you can get it away ftill more eafily. But
eafieft of all between L, C, M, where the quantity is lar-

geft, and the furface to attract and keep it back the ieafl.
When you have drawn away one of thefe angular porti-

ons of the fluid, another fucceeds in its place, from the

nature of fluidity and the mutual repulfion beforemention-

ed ; and fo the atmofphere continues flowing off at fuch
angle, like a flream, till no more is remaining. The ex-

tremities of the portions of atmofphere over thefe angular

parts are likewife at a greater diftance from the ele<arified

body, as may be fcQn by the infpeftion of the above figure; the point of the atmofphere of the angle C, being much

farther from C, than any other part of the atmofphere over
A the lines C, B, or B, : And befides the diftance arifing
from the nature of the figure, where the attraftion is lefs,

the particles will naturally expand to a greater diftance by
their mutual repulfion. On thefe accounts we fuppofe e-

leftrified bodies difcharge their atmofpheres upon unelec-

trifled bodies more eafily and at a greater diftance from

their angles and points than from their fmooth fides.—-

Thofe points will alfo difcharge into the air, when the bo-

dy has too great an eledtrical atmofphere, without bring-

ing any non-eledlric near, to receive what is thrown off:

For the air, though an electric perfey yet has always more or lefs water and other non-eledric matters mixed with it 3

and thefe attradl and receive what is ib difcharged. 17. But points have a property, by which they draw on

as well as throw offth.^ elcdlrical fluid, at greater diftances

I

than

^,
58 Mr B. FRANKLIN'S
"
than blunt bodies can. That is, as the pointed part of an eledlriiied body will difcharge the atmofphere of that body, or communicate it fartheft to another body, fo the point of an uneleftrified body, will draw off the eledrical atmofphere from an eledlrified body, farther than a blunter part of the fame uneleftrified body will do. Thus a pia. held by the head, and the point prefented to an eleftri fed: body, v/ill draw off its atmofphere at a foot diftance
;^
where if the head were prefented inftead of the point, no.
fuch effefl: would follow. To underftand this, we may
conlider, that if a perfon ftanding on the floor would: draw off the electrical atmofphere from an eleftrified bo-dy, an iron crow and a blunt knitting kneedle held alter-nately in his hand and prefented for that purpofc, do not draw with different forces in proportion to their different maffes. For the man, and what he holds in his hand, be
it large or fmall, are connefted with the common mafs
of uneleftrified matter ; and the force with which he
draws is the fame in both cafes, it conlifting in the different proportion of electricity in thq electrified body and
that common mafs. But the force with which the elec-
trified body retains its atmofphere by attradting it, is pro-^ portioned to the furface over which the particles are pla^ ced ', i. e. four fquare inches of that furface retain their atmofphere with four times the force that one fquare inch
retains its atmofphere. And asin plucking the hairs from,
the horfe's tail, a degree of ftrength infufficient to pull a-
way a handful at once, could yet eafily ftrip it hair by
hair

Letters on Electricity^

' 59

hair 5 To a blunt body prefented cannot draw ofF a num-
ber of particles at once, but a pointed one, with no great-

er force, takes them away eafily, particle by particle.

18. Thefe explanations of the power and operation of

points, when they firft occurred to me, and while they

my iirfl floated in

mind, appeared perfectly fatisfadory ;

but now I have wrote them, and confider'd them more

clofely in black and white, I mulT; own I have fome

doubts about them : yet as I have at prefent nothing bet-

'ter to oiFer in their ftead, I do not crofs them out : for

even a bad folution read, and its faults difcover'd, has of-

ten given rife to a good one in the mind of an ingenious

reader.

19. Nor is it of much importance to us, to know the

manner in which nature executes her lav/s 5 'tis enough
if we know the laws themfelves. 'Tis of real ufe to

know, that china left in the air unfupported will fall and

break ; but hew it comes to fall, and why it breaks, are

matters of fpeculation. 'Tis a pleafure indeed to know

'them, but we can preferve our china v»^ithout it.

20. Thus in the prefent cafe, to know this, power of

points, may poffibly be of fome ufe to mankind, though

we fliould never be able to explain it. The following

my experiments, as well as thofe in

firft paper, fliow this

power. I have a large prime conduftor made of feveral

thin fheets of Fuller's pafteboard form'd into a tube, near

10 feet long and a foot diameter. It is cover'd with

'Dutch embofs'd paper, almoft totally gilt. This large

I2

metallic

6o

Mr B. F R A N K L I N's

metallic furface fupports a much greater eleftrical atmojt
phere than a rod of iron of 50 times the weight would
do. It is fufpended by lilk lines, and, when charged will
ftrike at near two inches diftance, a pretty hard ftroke fo as to make one's knuckle ach. Let a perfoa flanding on the floor prefent the point of a needle at 12 or more inches diftance from it, and while the needle is fo prefented, the conduftor cannot be charged, the point draw* ing off the fire as fall as it is thrown on by the eleftrical globe. Let it be charged, and then prefent the point at the fame diftance, and it will fuddenly be difcharged. la
the dark you may fee a light on the point, when the exr periment is made. And if the perfon holding the point
ftands upon wax, he will be eledrified by receiving the fire at that diftance. Attempt to draw off the electricity with a blunt body, as a bolt of iron round at the. end and fmooth (a filverfmith's iron punch, inch-thick, is what I ufe) and you muft bring it within the diftance of threp inches before you. can do it,, and then it is done with a ftroke and crack. As the paftebbard tube hangs loofe on
filk lines, when you approach it with the. punch iron, it likewife will move towards the punch, being attrad:e.d
while it is charged 5 but if at the fame inftant a point be prefented as before, it retires again, for the point dif-
charges it. Take a pair of large brafa fcales, of two or more feet beam, the cords of the fcales being filk. Suf^ pend the beam by a packthread from the cieling,. fo that the bottom of the fcales may be about a foot from the
floor:.

Letters on Electricity.

6i

floor : The fcales will move round in a circle by the un-
twilling of the packthread. Set the iron punch on the
end upon the floor, in fuch a place as that the fcales may pafs over it in making their circle : Then eledlrify one fcale by applying the wire of a charged phial to It. As they move round, you fee that fcale drav/ nigher to the floor, and dip more when it comes over the punch ; and

if that be placed at a proper difl:ance,, the fcale will fnap

and difcharge its fire into it. But if a needle be ftuck

on the end of the punch, its point upwards, the fcale,

inftead of drawing nigh to the punch and fnapping, dif-

charges its fire filently through the point,, and rifes high-

er from the punch. Nay, even if the needle be placed

upon the floor near the punch, its point upwards, the
end of the punch, tho' fo much higher than the needle,

will not attraft the fcale and receive its fire, for the needle

will get it and convey it away, before it comes nigh e-

Bough for the punch to

ad:..

And
,

this

is conftantly ob-

fervable in thefe experiments, that the greater quantity

of eled:ricity on the pafteboard tube, the farther it ftrikes

or difcharges its fire, and the point likewife will draw it

off at a fliill greater diftance.
Now if the fire of elediricity and that of lightening be

the fame, as I have, endeavour'd to fhow at large in a

former paper,, this pafl:eboard tube and thefe fcales m.ay

reprefent eledrified clouds.. If a tube of only lo feet

long will ftrike and difcharge its fire on the punch at

two or three inches diftance, an eleftrified cloud of per-

haps

62 Mr B. franklin's
haps 10,000 acres, may ftrikeand difcharge on the earth at a proportionably greater diftance. The horizontal motion of the fcales over the floor, may reprefent the mo-
tion of the clouds over the earth ; and the eredt iron
punch, a hill or high building ; and then we fee how
eledtrified clouds paffing over hills or high buildings at
too great a height to ftrike, may be attracted lower till within their ftriking diftance. And laftly^ if a needle
iix'd on the punch with its point upright, or even on the floor below the punch, will draw the fire from the fcale
filently at a much greater than the ftriking diftance, and
fo prevent its defcending towards the punch 5 or if in its courfe it would have come nigh enough to ftrike, yet being firft deprived of its fire it cannot, and the punch is thereby fecured from the ftroke. I fay, if thefe things
are fo, may not the knowledge of this power of points beof ^u'fe to mankind, in preferving houfes, churches,
ihips,, &c. from the ftroke of lightning, by directing us to fix en the higheft parts of thofe edifices, upright rods of iron made fharp as a needle, and gilt to prevent ruft-
ing, and from the foot of thofe rods a wire down the outfide of the building into the ground, or down round one of the flirouds of a iliip, and down her fide till it reaches the water ? Would not thefe pointed rods proba-
bly draw the eleftrical fire filently out of a cloud before it came nigh enough to ftrike, and thereby fecure us from ithat moft fudden and terrible mifchief ?
21. To determine the queftion, whether the clouds
that

;

Letters on Electricity.

63

that contain lightning are eleftrified or not, I would pro-
pofe an experiment to be try'd where it may be done conve-
niently. On the top of fome high tower or fteeple, place a
kind of fentry-box, (as in Fig. 9.) big enough to contain a
man and an eleftrical ftand. From the middle of the ftand,

let an iron rod rife and pafs bending out of the door, and

then upright 20 or 30 feet, pointed very fharp at the end.
If the eleftrical ftand be kept clean and dry, a man ftanding on it when fuch clouds are palling low, might

be elcdtrified and afford fparks, the rod drawing fire
to him from a cloud,. If any danger to the man fhould
be apprehended (though I think there would be none)
let him ftand on the floor of his box, and now and then
bring near to the rod, the loop of a wire that has one
end faftened to the leads, he holding it by a wax handle
fo the fparks, if the rod is eledlrified, will ftrike from

die rod to the wire, and not affe£l him,,

22. Before I leave this fubje£t of lightning, I may men-

tion fome other fimilarities betw^een the effefts of that,

and thefe of eleftricity., Lightning has often been known

A to ftrike people blind,.

pigeon that we ftruck dead to

appearance by the eledrical fhock, recovering life, droop'd

about the yard feveral days, eat nothing though crumbs

We were thrown to it, but declined and died.

did not

think of its being deprived of fight ; but afterw^ards a

pullet ftruck dead in like manner, being recovered by re-
peatedly blowing into its lungs, when fet down on the

floor, ran headlong againft_ the wall^ and on examination

appear-

64

Mr B. F R A N K L I N's

appeared perfedlly blind. Hence we concluded that the

pigeon alfo had been abfolutely blinded by the fhock*
The biggeft animal we have yet killed or try*d to kill

with the electrical ftroke, was a well -grown pullet.

23. Reading in the ingenious Dr. Hales ^ account of

the thunder ftorm at Stretham^ the eflfefl: of the lightning

in ftripping off all the paint that had covered a gilt

moulding of a pannel of wainfcot, without hurting the

reft of the paint, I had a mind to lay a coat of paint

over the filleting of gold on the cover of a book, and

try the effefl: of a ftrong eleftrical flafh fent through that

gold from a charged fheet of glafs. But having no paint

at hand, I pafted a narrow ftrip of paper over it ; and

when dry, fent the flafh through the gilding ; by which

the paper was torn off from end to end, with fuch force,

that it was broke in feveral places, and in others brought

away part of the grain of the Turky-leather in which

it was bound 5 and convinced me, that had it been paint-

ed, the paint would have been ftript off in the fame

manner with that on the wainfcot at Stretham,
24. Lightning melts metals, and I hinted in my pa-

per on that fubjed:, that I fufpefted it to be a cold fu-

fion ; I do not mean a fufion by force of cold, but a

We fufion without heat.

have alfo melted gold, filver,

and copper, in fmall quantities, by the eledlrical flafh.
The manner is this : Take leaf gold, leaf filver, or leaf

gilt copper, commonly called leaf brafs or Dutch gold : cut off from the leaf long narrow ftrips the breadth of

a flraw.

Letters on Electricity.

65

a ftraw. Place one of thefe ftrips between two ftrips of

fmooth glafs that are about the width of your ifinger. If

one ftrip of gold, the length of the leaf, be not long e-

nough for the glafs, add another to the end of it, fo that

you may have a little part hanging out loofe at each end

of the glafs. Bind the pieces of glafs together from end

to end with ftrong filk thread ^ then place it fo as to be

part of an eledrical circle, (the ends of gold hanging out

being of ufe to join with the other parts of the circle)

and fend the flafh through it, from a large eledlrified

jar or flieet of glafs. Then if your ftrips of glafs remain

whole, you will fee that the gold is miffing in feveral

|daces, and inftead of it a metallic ftain on both the

glafles y the ftains on the upper and under glafs exadlly limilar in the minuteft ftroke, as may.be feen by holding

them to the light; the metal appeared to have been not

«only melted, but even. vitrified, or otherwife fo driven

into the pores of the glafs, as to be protefted by it from

the adion of the ftrongeft Aqua Fortis and jig: Regia. I

fend you enclofed two little pieces of glafs with thefe

metallic ftains upon them, which cannot be removed with-

out taking part of the glafs v/ith them. Sometimes the

ftain fpreads a little wider than the breadth of the leaf,

and looks brighter at the edge, as by infpecSing clofely

you may obferve in thefe. Sometimes the glafs breaks

to pieces : once the upper glafs broke into a thoufand pie-

ces, looking like coarfe fait. Thefe pieces I fend you, were

ftain'd with Dutch gold. True gold makes a darker ftain,

K

fomewhat

;

66 Mr B. franklin's

We fomewhat reddijfh ; filver, a grcenifh ftain.

once took

two pieces of thick looking-glafs, as broad as a Gunter's

fcale, and 6 inches long ; and placing leaf gold between

them, put them betwixt two fmoothly plaln'd pieces of

wood, and fix d them tight in a book-binder's fmall prefs

yet though they were fo clofely confined, the force of the
eletlrical fhock (hivered the glafs into many pieces. The gold was melted and ftain d into the glafs as ufiial. The circumftances of the breaking of the glafs differ much

in making the experiment, and fometimes it does not

break at all : but this is conftant, that the ftains In the

upper and under pieces are exad: counterparts of each o-

ther. And though I have taken up the pieces of glafs

my between

fingers immediately after this melting, I ne-

ver could perceive the leaft warmth in them.
25. In one of my former papers, I mentioned, that
gilding on a book, though at firft it communicated the

jGhock perfedly well, yet fail'd after a few experiments,

We which we could not account for.

have fince found,

that one ftrong Ihock breaks the continuity of the gold

in the filleting, and makes it look rather like duft of

gold, abundance of its parts being broken and driven ofF^.

and it will feldom condudt above one flrong fhock. Per-

haps this may be the reafon ; when there is not a perfedt
continuity in the circle, the fire muft leap over the va-

cancies 3 there is a certain diftance which it is able to leap over according to its ftrength j if a number of

finall vacancies, though each be very minute, taken to-

gether

Letters ^/^Electricity,

67

gether exceed that diftance, it cannot leap ovfer then33

and fo the ihock is prevented,

26. From the before mentioned law of eledricity, that
points, as they are more or lefs acute, draw on and

throw off the eleftrical fluid with more or lefs power,

and at greater or lefs diftances, and in larger or fmaller
quantities in the fame time, we may fee how to account

for the iituation of the leaf of gold fufpended between

two plates, the upper one continually eleftrified, the un-
der one in a perfon's hand (landing on the floor. When

the upper plate is eledtrified, the leaf is attracted and

raifed towards it, and would fly to that plate were it not
for its own points. The corner that happens to be up-

permoft when the leaf is rifing, being a {harp point, from

the extream thinnefs of the gold, draws and receives at

a diflance a fufficient quantity of the electrical fluid to

•give itfelf an eledrical atmofphere, by which its progrefs

to the upper plate is ftopt, and it begins to be repelled

from that plate, and would be driven back to the

under plate, but that its lowefl: corner is likewiie a

point, and throws off or difcharges the overplus of the

leaf's atmofphere, as faft as the upper corner draws it

on. Were thefe two points perfediy equal in acutenefs,

the leaf would take place exa(£Uy in the middle fpace,

for its Weight is a trifle, compared to the power acting

on it : But it is generally neareft: the uneledirified plate,

becaufe, when the leaf is offered to the eleftrined plate

at a difl:ance, the (harpefl: point is commonly firft affeded

and raifed towards it ; fo that point, from its greater a-

K2

cute-

68 Mr B. franklin's
cutenefs, receiving the fluid fafler than its oppofite can
difcharge it at equal diflances, it retires from the eleftrrfied plate, and draws nearer to the uneledlrified plate, till it comes to a diflance where the difcharge can be exaftly equal to the receipt, the latter being leflcned, and the former encreafed^ and there it remains as long as the globe continues to fupply frefh eledtrieal matter. This
will appear plain, when the difference of acutenefs in the corners is made very great. Cut a piece of Dutch
gold (which is fitteft for thefe experiments on account of its greater ftrength) into the form of Fig. id the upper corner a right angle, the two next obtufe angles, and the lowefl a very acute one ; and bring this on your plate under the eledlrified plate, in fuch a manner as
that the right-angled part may be firft raifed (which is
done by covering the acute part with the hollow of your
hand) and you will fee this leaf take place much nearer
to the upper than to the under plate ; becaufe, without being nearer, it cannot receive fo fall at its right-angled
point, as it can difcharge at its acute one. Turn thris
leaf with the acute part uppermoft, and then it takes
place nearefl: the unelecSrified plate, becaufe otherwife it receives fafter at Its acute point than it can difcharge
at its right-angled one. Thus the difference of diftance
is always proportioned to the difference of acutenefs.
Take care in cutting your leaf to leave no little ragged particles on the edges, which fometimes form points where you would not have them. You may make this
figure

Letters on Electricity.

69

figure fo acute below and blunt above, as to need no under

When plate, it difcharging faft enough into the air.

it is

made narrower, as the figure between the pricked lines,

we call it the Golden Fijhy from its manner of adling. For

if you take it by the tail, and hold it at a foot or greater

horizontal diftance from the prime condudtor, it will,

when let go, fly to it with a brifk but wavering motion,

like that of an eel through the water -, it will then take

place under the prime condudlor, at perhaps a quarter

.or half an inch diflance, and keep a continual fhaking of

:its tail like a fifh, fo that it feems. animated. Turn its tail
towards the prime conduftor, and then it flies to your
finger, and feems to nibble it. And if you hold a plate

under it at fix or eight inches diftance, and ceafe turning
the Globe, when the electrical atmofphere of the conductor grows fmall, it will defcend to the plate and fwim bac5k

again feveral times with the fame fiHi-like motion, greatly
to the entertainment of fpedtators. By a little praftice in

.blunting or Iharpening the heads or tails of thefe figures,

jou may make them take place as defired, nearer, or

farther from the eledrified plate.

27. It is faid in fedtion 8, of this paper, that all kinds of
common matter are fuppofed not to attract the electrical

fluid with equal fl:rength 3 and that thofe called eledtrics "per fe^ as glafs, &c. attraft and retain it ftrongeft, and con-
tain the greatefl: quantity. This latter pofition may fcem

a paradox to fome, being contrary to the hitherto received

opinion ; and therefore I fhall now endeavour to explain it.

28. In

yo

Mr B. F R A N K L I N's

28 In order to this, let it firft be confidered, that we ,cannot^ by any means we are yet acquainted with^ force the e^
leBricalfluid thro glafs. I know it is commonly thought
that it eafily pervades glafs, and the experiment of a feather fufpended by a thread in a bottle hermetically fealed, yet
moved by bringing a nibbed tube near the outfide of the
bottle, is alledged to prove it. But, if the eleftrical fluid
io eafily pervades glafs, how does the vial become char^ ged (as we term it) when we hold it in our hands ? Would not the fire thrown in by the wire pafs through to our hands, and fo efcape into the floor ? Would not the bottle in that cafe be left juft as we found it, uncharged, as we know a metal bottle fo attempted to be char-
ged would be ? Indeed, if there be the leaft crack, the minuteft folution of continuity in the glafs, though it re-
mains fo tight that nothing elfe we know of will pafs, yet
the extremely fubtile eledtrical fluid flies through fuch
a crack with the greateft freedom, and fuch a bottle wc know can never be charged : What then makes the diffe-
rence betv/een fuch a bottle and one that is found, but this, that the fluid can pafs through the one, and not through the other ? *
29. It is true there Is an experiment that at firft fight
would be apt to fatisfy a flight obferver, that the fire thrown into the bottle by the wire, does really pafs thro*

my * See the firft fixteen Sedions of

former Paper, called Farther Ex-

pmments^ &c.

the

Lettters on Electricity.

71

the glafs. It is this : place the bottle on a glafs ftandj under the prime condudlor ; fufpend a bullet by a chain from the prime conduftor, till it comes within a quarter of an inch right over the wire of the bottle ; place your knuckle on the glafs ftand, at juft the fame diftance from the coating of the bottle, as the bullet is from its wire. Nov/ let the globe be turned, and you fee a fpark ftrike from the bullet to the wire of the bottle, and the fame inftant you fee and feel an exadlly equal fpark ftriking from the coating on your knuckle, and fo on fpark for fpark. This looks as if the whole received by the bottle was again dif-
charged from it. And yet the bottle by this means is charged ! * And therefore the fire that thus leaves the
bottle, though the fame in quantity, cannot be the very fame fire that entered at the wire \ for if it were, the bottle would remain uncharged.
30. If the fire that fo leaves the bottle be not the fame that is thrown in through the wire, it muft be fire that fubfifted in the bottle, (that is, in the glafs of the bottle) be-
fore the operation began.
31. If fo, there muft be a great quantity in glafs, becaufe a great quantity is thus difcharged even from very
thin glafs.
32. That this eledrical fluid or fire is ftrongly attrafted
by glafs, we know from the quicknefs and violence with
which it is refumed by the part that had been deprived of

^ Sec § 10 of Farther ExperimsntSy &c.
it.

72

Mr B, FRANKLIN'S

it, when there is an opportunity. And by this, that we

cannot from a mafs of glafs draw a quantity of eledlrical

fire, or eleilrify the whole mafs minus^ as we can a mafs of

We metal.

cannot leffen or increafe its whole quantity,

for the quantity it has it holds ; and it has as much as it can hold. Its pores are filled with it as full as the mu-

tual repellency of the particles will admit ; and what is al-

ready in, refufes, or ftrongly repels, any additional quantity.
Nor have we any way of moving the eledtrical fluid in

glafs, but one ; that is, by covering part of the two furfa-

ces of thin glafs with non-eleftrics, and then throwing aa

additional quantity of this fluid on one furface, which

fpreading in the non-eledric, and being bound by it to

that furface, aSs by its repelling force on the particles of the

cleftrical fluid contained in the other furface, and drives

them out of the glafs into the non-eleftric on that jfide, from whence they are difcharged, and then thofe added on the charged fide can enter. But when this is done,

there is no. more in the glafs, nor lefs than before, jufl: as

much having left it on one fide as it received on the other. 33. I feel a want of terms here, and doubt much whe-
ther I ihall be able to make this part intelligible. By the

vjovdifiirfacey in this cafe, I do not mean mere length and
breadth without thicknefs V b\it when! fpeak of the up-
per or under furface of a piece of glafs, the o^te^ or in-

ner furface of the vial, I mean length, breadth, and half

the thicknefs, and beg the favour of being fo underftood.

Now, I fuppofe, that glafs in its firfl: principles, and in the

furnace.

'^^f^^*y^ ooujt,.

Letters on Electricity.

73

Furnace, has no more of this eledtrical fluid than other

common matter : That when it is blown, as it cools, and

the particles of common fire leave it, its pores become a va-

cuum : That the component parts of glafs are extremely

fmall and fine, I guefs from its never fhowing a rough

face when it breaks, but always a polifh ; and from the

fmallnefs of its particles I fuppofe the pores between them

muft be exceeding fmall, which is the reafon that Aqua-

fortis, nor any other menftruum we have, can enter to fe-

parate them and diflblve the fubflance ; nor is any fluid

we know of, fine enough to enter, except common fire,

Now and the eleftrical fluid.

the departing fire leaving

a vacuum, as aforefaid, between thefe pores, which air

nor water are fine enough to enter and fill, the eledirical
fluid (which is every where ready in what we call the

non-eleftrics, and in the non-eleftric Mixtures that are in

the air, is attracted in : yet does not become fixed with the

fubftance of the glafs, but fubfifl:s there as water in a po-

rous ftone, retained only by the attradion of the fixed

parts, itfelf flill loofe and a fluid. But I fuppofe farther,

that in the cooling of the glafs, its texture becomes clofefl:

in the middle, and forms a kind of partition, in which the

pores are fo narrow, that the particles of the elecflrical

fluid, which enter both furfaces at the fame time, cannot

go through, or pafs and repafs from one furface to the

other, and fornix together; yet, though the particles of e-

ledlrical fluid, imbibed by each furface, cannot themfelves

L

pafs

74

Mr B. F R A N K L I N's

pafs through to thofe of the other, their repellency can,
and by this means they aft on one another. The particles

of the eleflirical fluid have a mutual repellency, but by the

power of attraftion in the glafs they are condenfed or for-

When ced nearer to each other.

the glafs has received

and, by its attradlion, forced clofer together fo much of

this ele£lrified fluid, as that the power of attrading and

condenfmg in the one, is equal to the power of expanfion

in the other, it can imbibe no more^ and that remains its

conftant whole quantity ^ but each furface would receive more, if the repellency of what is in the oppofite furface
did not relift its entrance. The quantities of this fluid in

each furface being equal, their repelling aftion on each

other is equal ; and therefore thofe of one furface cannot

drive out thofe of the other : but> if a greater quantity is

forced into one furface than the glafs would naturally

draw in ', this increafes the repelling power on that fide,

and overpowering the attraction on the other, drives out

part of the fluid that had been imbibed by that furface, if

there be any non-ele6lric ready to receive it: fuch there is ia

all cafes where glafs is eledtrified to give a fhock. The fur-

face that has been thus emptied by having its eleftrical

fluid driven out, refumes again an equal quantity with vio-

lence, as foon as the glafs has an opportunity to difchargc

that over-quantity more than it could retain by attraftion

in its other furface, by the additional repellency of which the vacuum had been occafioned. For experiments fa-

vouring

Letters on Electricity.

75

vouring (If I may not fay confirming) this hypothejGs, I

muft, to avoid repetition, beg leave to refer you back to

my what is faid of the eledrical phial in

former pa-

pers,
34. Let us now fee how it will account for feveral o-
— ther appearances. Glafs, a body extremely elaftic (and
perhaps its elafticity may be owing in fome degree to the
fublifting of fo great a quantity of this repelling fluid
in its pores) muft, when rubbed, have its rubbed fur-
face fomewhat ftretched, or its folid parts drawn a little farther afunder, fo that the vacancies in which the electrical fluid refldeg, become larger, affording room for more of that fluid, which is immediately attraded into it from the cufhion or hand rubbing, they being fupply'd
from the common flock. But the inflant the parts of the
glafs fo open d and fiU'd have pafs'd the fridtion, they clofe again, and force the additional quantity out upon the furface, where it mufl refl till that part comes round to the cufhion again, unlefs fome non eledric (as the prime condu6tor) firft prefents to receive it/" But if the infide of the globe be lined with a non-eledric, the ad-

* In the dark the eledrical fluid may be feen on the cufhion in two fe-
rai-circles or half- moons, one on the fore part, the other on the back part of the cufhion, juft where the globe and cufhion feparate. In the fore crefcent the fire is pafRng out of the cufhion into the glals ; in the other it is leaving the glafs, and returning into the back part of the cufliion.
When the prime condudor is apply'd to take it off' the glafs, the back
crefcent difappears.

L.

ditiona!

76

Mr B. FR ANKL IN^^

ditional repellency of the ele(ftrical fluid, thus colledled by fridlion on the rubb'd part of the globe's outer fur-

face, drives an equal quantity out of the inner furface into
that non-eledric lining, which receiving it, and carrying
it away from the rubb'd part into the common mafs,

through the axis of the globe and frame of the machine, the new colledted eledlrical fluid can enter and re-

main in the outer furface, and none of it (or a very little) will be received by the prime conductor. As this charg'd

part of the globe comes round to the cufhion again, the

outer furface delivers its overplus fire into the cufhion,

the oppofite inner furface receiving at the fame time an

equal quantity from the floor. Every electrician knows

that a globe wet within will afford little or no fire, but

the reafon has not before been attempted to be given,

that I know of.

34.

So if a tube lined with a non-eleftric, be rubb'd, -f*

little or no fire is obtained from it. What is colleded

from the hand in the downward rubbing ftroke, entering

the pores of the glafe, and driving an equal quantity out

of the inner furface into the non-eledbric lining : and the

hand in pafling up to take a fecond ftroke, takes out a-

^ain what had been thrown into the outer furface, and

then the inner furface receives back again what it had

given to the non-eleilric lining. Thus the particles of

t Gilt paper, with the gilt face next the glafsj does well.
eleftrical

Letters on Electricity.

^77

ele(5trical fluid belonging to the infide furface go in and out of their pores every ftroke given to the tube. Put a wire into the tube, the inw^ard end in contact v^ith the non-elecStric Hning, fo it will reprefent the heyden bottle. Let a fecond perfon touch the wire while you rub, and
the fire driven out of the inward furface when you give the ftroke, will pafs through him into the common mafs, and return through him when the inner furface refumes its quantity, and therefore this new kind of Leyden bottle cannot fo be charged. But thus it may : after every ftroke, before you pafs your hand up to make anothei*,
let the fecond perfon apply his finger to the wire, take
the fpark, and then withdraw his finger ; and fo on till he has drawn a number of fparks \ thus will the inner furface be exhaufted, and the outer furface charged 5 then wrap a ftieet of gilt paper clofe round the outer furface,
and grafping it in your hand you may receive a ftiock
by applying the finger of the other hand to the wire :
for now the vacant pores in the inner furface refume
their quantity, and the overcharg'd pores in the outer furface difcharge that overplus ; the equilibrium being reftored through your body, which could not be reftored through the glafs.* If the tube be exhaufted of air, a non eledtric lining in contact with the wire is not neceffary \ for in vacuo^ the elecSrical fire will fly freely from

* See farther experiments, § 15.

the

78

Mr B. F R A N K L I N's

the inner flirface, without a non-ele6tric conduftor "i but air refills its motion ; for being itfelf an eleftric per

fe, it does not attradl it, having already its quantity. So

the air never draws off an eledlric atmofphere from any
,

body, but in proportion to the non-eleftrics mix'd with

it : it rather keeps fuch an atmofphere confined, which

from the mutual repulfion of its particles, tends to diffi-
— pation, and would immediately diffipate in vacuo, And

thus the experiment of the feather inclofed in a glafs

veffel hermetically fealed, but moving on the approach
of the rubbed tube, is explained : When an additional

quantity of the eledirical fluid is applied to the fide of

the veffel by the atmofphere of the tube, a quantity is

repelled and driven out of the inner furface of that fide

into the veffel, and there affeils the feather, returning a--
gain into its pores, when the tube with its atmofphere is

withdrawn ; not that the particles of that atmofphere did

themfelves pafs through the glafs to the feather.

And

every other appearance I have yet feen, in which glafs

and eledlricity are concern'd, are, I think, explained with

equal eafe by the lame hypothefis. Yet, perhaps, it may

not be a true one, and I Ihall be obliged to him that af-
fords me a better.

35. Thus I take the difference between non eledrics and glafs, an eleftric perfcy to confift in thefe two par-

ticulars. I ft. That a non-eleftric eafily fuffers a change.
in the quantity of the eledrical fluid it contains* You may

9

Lettters on Electricity.

76

may leffen its whole quantity by drawing out a part,
which the whole body will again refume ; but of glafs you can only leflen the quantity contained in one of its furfaces^ and not that, but by fupplying an equal quantity at the fame time to the other furface 5 fo that the whole giafs may always have the fame quantity in the two furfaces, their two different quantities being added together.
And this can only be done in glafs that is thin \ beyond a certain thicknefs we have yet no power that can make
this change. And, 2dly, that the eleftrical fire freely removes from place to place, in and through the fubftance of a non-eledtric, but not fo through the fubftance of glafs. If you oifer a quantity to one end of a long rod
of metal, it receives it, and when it enters, every par-
ticle that was before in the rod, pufhes its neighbour quite to the further end, where the overplus is difcharg'd; and this inftantaneoufly where the rod is part of the circle in the experiment of the fhock. But glafs, from the fmallnefs of its pores, or ftronger attradlion of what it contains, refufes to admit fo free a motion 5 a glafs rod will not condudl a (hock, nor will the thinneft glafs fuffer any particle entring one of its furfaces to pafs thro'
to the other.
36. Hence we fee the impoffibility of fuccefs, in the
experiments proposed, to draw out the eiHuvial virtues of a non-eledric, as cinnamon for inftance, and mixing them with the elecSrical fluid, to convey them with that into
the

8o

Mr B. F R A N K L I N's

tlie body, by Including It in the globe, and then apply-

ing friftion, &c. For though the effluvia of cinnamon,

and the electrical fluid fhould mix within the globe, they

would never come out together through the pores of the

glafs, and fo go to the prime condu<fi:or ; for the elec-

trical fluid itfelf cannot come through 5 and the prime conduftor is always fupply'd from the cufhlon, and that
from the floor. And befides, when the globe is filled

with cinnamon, or other non-eledtric, no eledlrical fluid

can be obtained from its outer furface, for the reafon be-

fore-mentioned. I have try*d another way, which I

thought more likely to obtain a mixture of the eleilrical and

other effluvia together, if fuch a mixture had been poffible.

my I placed a glafs plate under

cufhion, to cut off the

communication between the cufhion and floor 5 then brought a fmall chain from the cufhion into a glafs of

oil of turpentine, and carried another chain from the oil

of turpentine to the floor, taking care that the chain from

the cufhion to the glafs touch'd no part of the frame of

the machine. Another chain was fix'd to the prime

condadlor, and held in the hand of a perfon to be elec-

trifed. The ends of the two chains in the glafs were

near an inch diflant from each other, the oil of turpen-

Now tine between.

the globe being turned, could draw

no fire from the floor through the machine, the commu-

nication that way being cut oflf by the thick glafs plate

under the cufhion : it muft then draw it through the

chains

Letters on Electricity.

8i

chains whofe ends were dipt in the oil of turpentine.
And as the oil of turpentine being an eledric per fe^ would

not conduct what came up from the floor, was obliged to

jump from the end of one chain, to the end of the other>^
through the fubftance of that oil, which we could fee.

in large fparks j and fo it had a fair opportunity of feizing

fome of the fineft particles of the oil in its palTage, ,and

carrying them off with it : but no fuch effed: followed,,

nor could I perceive the leaft difference in the fmell of

the ele(5trical effluvia thus collefled, from what it has

when collected other wife ; nor does it otherwife affed: the

body of a perfon eled:rifed. I likewife put into a phial,

inftead of water, a llrong purgative liquid, and then

charged the phial, and took repeated fliocks from it, in

which cafe every particle of the eleftrical fluid mufl:, be-
fore it went through my body, have firfl gone through

the liquid when the phial is charging, and returned

through it when difcharging, yet no other effed followed

than if it had been charged with water. I have alfo fmelt

the electrical fire when drawn through gold, filver, cop-

per, lead, iron, wood, and the human body, and could

perceive no difference > the odour is always the fame

"where the fpark does not burn what it ftrikes y and

therefore I imagine it does not take that fmell from any

quality of the bodies it paffes through. And indeed, as

that fmell fo readily leaves the eledrical matter, and ad-

heres to the knuckle receiving the fparks, nnd to other

M

things

;

82 Mr B. FRANKLIN^s

things ; I fufped: that it never was conneded with it, but arifcs inftantaneoufly from fomething in the air afted

upon by it. For if it was fine enough to come with the
cleitrical fluid through the body of one perfon, why

fhould it flop on the ikin of another ?

my But I fhall never have done, if 1 tell you all

con-

jeftures, thoughts, and imaginations, on the nature and

operations of this eledlrical fluid, and relate the variety
of little experiments we have try'd. I have already made

this .paper too long, for which I mufl: crave pardon, not
having now time to make it fhorter. I {hall only add,

that as it has been obferved here that fpirits will fire by the eleftrical fpark in the fummer time, without heating
them, when Fahrenheit's thermometer is above 70 5 fo^ when colder, if the operator puts a fmall flat bottle

of fpirits in his bofom, or a clofe pocket, with the fpoon>

fome little time before he ufes them, the heat of his body will communicate warmth more than fufficicnt for the

purpofe.

ADDt

Letters on Electricitv.

^[3

ADDITIONAL EXPERIMENT, /rm;?^ that the Ley-
den Bottle has no more electrical Fire in it 'when charged^ than before \ nor lefs when difcharged: That in difcharging^ the Fire does not ijjuefrom the Wire and the Coating at thefame Time^ as fome have thought^ but that the Coatiiig always receives what is difcharged by the Wire^ or an equal ^antity ^ the outer Surface being always in a negative State of Eledtricity^ when the inner Surface is 171 a pofitive State.

PL A E C a thick plate of glafs under the rubbing cufhion, to cut off the communication of elediri-

cal jfire from the floor to the culhionj then, if

there be no fine points or hairy threads flicking out from

the cufhion, or from the parts of the machine oppofite to

the cufjiion, (of which you mufl be careful) you can get

but a few fparks from the prime conduftor, which are all

the cufliion will part with.

Hang a phial then on the prime condudor, and it will

not charge, tho' you hold it by the coating.

But

Form a communication by a chain from the coating to
the cufhion, and the phial will charge.

For the globe then draws the eleftrical fire out of the

outfide furface of the phial, and forces it, through the

-prime conduftor and wire of the phial, into the infide

furface.
,'-.:hr;

Ma

Thus

84 Mr B. franklin's

Thus the bottle is charged with its own fire, no other

being to be had while the glafs plate is under the cufhion.

Hang two cork balls by flaxen threads to the prime con-

dudlor J

then touch

the

coating

of

the bottle,

and

they

will be eleftrified and recede from each other.

For jufl as much fire as you give the coating, fo much

is difcharged through the wire upon the prime condudlor, whence the cork balls receive an elecflrical atmofphere. But
Take a wire bent in the form of a C, with a ftick of wax fixed to the outfide of the curve, to hold it by ; and
apply one end of this wire to the coating, and the other at

the fame time to the prime conduftor, the phial will be

difcharged 5 and if the balls are not eledtrified before the difcharge, neither will they appear to be fo after the difcharge, for they will not repel each other.
Now if the fire difcharged from the infide furface of
the bottle through its wire, remained on the prime con-

duftor, the balls would be eledtrified and recede from

each other.

If the phial really exploded at both ends, and difchar-

ged fire from both coating and wire, the balls would be

more eledtrified and recede farther : for none of the fire
can efcape, the wax handle preventing.

But if the fire, with which the infide furface is furchar-
ged, be fo much precifely as is wanted by the outfide fur-

face, it will pafs round through the wire fixed to the wax

handle^