Transcriber's note: Text enclosed by underscores is in italics (_italics_).
In view of the difficulty of reliably distinguishing 18th-century variant
spellings from typographical errors, the text has been reproduced entirely
as printed.
* * * * *
EXPERIMENTS
AND
OBSERVATIONS
ON
ELECTRICITY,
MADE AT
_Philadelphia_ in _America_,
BY
Mr. BENJAMIN FRANKLIN,
AND
Communicated in several Letters to Mr. P. COLLINSON,
of _London_, F. R. S.
* * * * * *
_LONDON_:
Printed and sold by E. CAVE, at _St. John's Gate_. 1751.
(_Price 2s. 6d._)
The PREFACE.
_It may be necessary to acquaint the reader, that the following
observations and experiments were not drawn up with a view to their being
made publick, but were communicated at different times, and most of them in
letters wrote on various topicks, as matters only of private amusement._
_But some persons to whom they were read, and who had themselves been
conversant in electrical disquisitions, were of opinion, they contain'd so
many curious and interesting particulars relative to this affair, that it
would be doing a kind of injustice to the publick, to confine them solely
to the limits of a private acquaintance._
_The Editor was therefore prevailed upon to commit such extracts of
letters, and other detach'd pieces as were in his hands to the press,
without waiting for the ingenious author's permission so to do; and this
was done with the less hesitation, as it was apprehended the author's
engagements in other affairs, would scarce afford him leisure to give the
publick his reflections and experiments on the subject, finish'd with that
care and precision, of which the treatise before us shews he is alike
studious and capable. He was only apprized of the step that had been thus
taken, while the first sheets were in the press, and time enough for him to
transmit some farther remarks, together with a few corrections and
additions, which are placed at the end, and may be consulted in the
perusal._
_The experiments which our author relates are most of them peculiar to
himself; they are conducted with judgment, and the inferences from them
plain and conclusive; though sometimes proposed under the terms of
suppositions and conjectures._
_And indeed the scene he opens, strikes us with a pleasing astonishment,
whilst he conducts us by a train of facts and judicious reflections, to a
probable cause of those phænomena, which are at once the most awful, and,
hitherto, accounted for with the least verisimilitude._
_He exhibits to our consideration, an invisible, subtile matter,
disseminated through all nature in various proportions, equally unobserved,
and, whilst all those bodies to which it peculiarly adheres are alike
charged with it, inoffensive._
_He shews, however, that if an unequal distribution is by any means brought
about; if there is a coacervation in one part of space, a less proportion,
vacuity, or want, in another; by the near approach of a body capable of
conducting the coacervated part to the emptier space, it becomes perhaps
the most formidable and irresistible agent in the universe. Animals are in
an Instant struck breathless, bodies almost impervious by any force yet
known, are perforated, and metals fused by it, in a moment._
_From the similar effects of lightening and electricity our author has been
led to make some propable conjectures on the cause of the former; and at
the same time, to propose some rational experiments in order to secure
ourselves, and those things on which its force is often directed, from its
pernicious effects; a circumstance of no small importance to the publick,
and therefore worthy of the utmost attention._
_It has, indeed, been of late the fashion to ascribe every grand or unusual
operation of nature, such as lightening and earthquakes, to electricity;
not, as one would imagine, from the manner of reasoning on these occasions,
that the authors of these schemes have, discovered any connection betwixt
the cause and effect, or saw in what manner they were related; but, as it
would seem, merely because they were unacquainted with any other agent, of
which it could not positively be said the connection was impossible._
_But of these, and many other interesting circumstances, the reader will be
more satisfactorily informed in the following letters, to which he is
therefore referred by_
_The_ EDITOR.
[Illustration]
LETTER I.
FROM
Mr BENJ. FRANKLIN, in _Philadelphia_.
TO
Mr PETER COLLINSON, F.R.S. _London_.
_July 28, 1747_.
_SIR_,
THE necessary trouble of copying long letters, which perhaps when they come
to your hands may contain nothing new, or worth your reading (so quick is
the progress made with you in Electricity) half discourages me from writing
any more on that subject. Yet I cannot forbear adding a few observations on
M. _Muschenbroek_'s wonderful bottle.
1. The non-electric contain'd in the bottle differs when electrised from a
non-electric electrised out of the bottle, in this: that the electrical
fire of the latter is accumulated _on its surface_, and forms an electrical
atmosphere round it of considerable extent: but the electrical fire is
crouded _into the substance_ of the former, the glass confining it.
2. At the same time that the wire and top of the bottle, &c. is electrised
_positively_ or _plus_, the bottom of the bottle is electrised _negatively_
or _minus_, in exact proportion: _i. e._ whatever quantity of electrical
fire is thrown in at top, an equal quantity goes out of the bottom. To
understand this, suppose the common quantity of Electricity in each part of
the bottle, before the operation begins, is equal to 20; and at every
stroke of the tube, suppose a quantity equal to 1 is thrown in; then, after
the first stroke, the quantity contain'd in the wire and upper part of the
bottle will be 21, in the bottom 19. After the second, the upper part will
have 22, the lower 18, and so on 'till after 20 strokes, the upper part
will have a quantity of electrical 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 spued back thro' the wire, or flies out in loud cracks thro'
the sides of the bottle.
3. The equilibrium cannot be restored in the bottle by _inward_
communication or contact of the parts; but it must be done by a
communication formed _without_ the bottle, between the top and bottom, by
some non-electric, touching both at the same time; in which case it is
restored with a violence and quickness inexpressible: or, touching each
alternately, in which case the equilibrium is restored by degrees.
4. As no more electrical fire can be thrown into the top of the bottle,
when all is driven out of the bottom, so in a bottle not yet electrised,
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 electric _per se_. Again, when the bottle is electrised, but
little of the electrical fire can be _drawn out_ from the top, by touching
the wire, unless an equal quantity can at the same time _get in_ at the
bottom. Thus, place an electrised bottle on clean glass or dry wax, and you
will not, by touching the wire, get out the fire from the top. Place it on
a non-electric, and touch the wire, you will get it out in a short time;
but soonest when you form a direct communication as above.
So wonderfully are these two states of Electricity, the _plus_ and _minus_,
combined and balanced in this miraculous bottle! situated and related to
each other in a manner that I can by no means comprehend! If it were
possible that a bottle should in one part contain a quantity of air
strongly comprest, and in another part a perfect vacuum, we know the
equilibrium would be instantly restored _within_. But here we have a bottle
containing at the same time a _plenum_ of electrical fire, and a _vacuum_
of the same fire; and yet the equilibrium cannot be restored between them
but by a communication _without_! though the _plenum_ presses violently to
expand, and the hungry vacuum seems to attract as violently in order to be
filled.
5. The shock to the nerves (or convulsion rather) is occasion'd by the
sudden passing of the fire through the body in its way from the top to the
bottom of the bottle. The fire takes the shortest course, as Mr _Watson_
justly observes: But it does not appear, from experiment, that, in order
for a person to be shocked, a communication with the floor is necessary;
for he that holds the bottle with one hand, and touches the wire with the
other, will be shock'd as much, though his shoes be dry, or even standing
on wax, as otherwise. And on the touch of the wire (or of the gun-barrel,
which is the same thing) the fire does not proceed from the touching finger
to the wire, as is supposed, but from the wire to the finger, and passes
through the body to the other hand, and so into the bottom of the bottle.
EXPERIMENTS _confirming the above_.
EXPERIMENT I.
Place an electrised phial on wax; a small cork-ball suspended by a dry
silk-thread held in your hand, and brought near to the wire, will first be
attracted, and then repelled: when in this state of repellency, sink your
hand, that the ball may be brought towards the bottom of the bottle; it
will there be instantly and strongly attracted, 'till it has parted with
its fire.
If the bottle had an electrical atmosphere, as well as the wire, an
electrified cork would be repelled from one as well as from the other.
EXPERIMENT II.
FIG. 1. From a bent wire (_a_) sticking in the table, let a small linen
thread (_b_) hang down within half an inch of the electrised phial (_c_).
Touch the wire of the phial repeatedly with your finger, and at every touch
you will see the thread instantly attracted by the bottle. (This is best
done by a vinegar cruet, or some such belly'd bottle). As soon 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_) so 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
distance. Then electricise the bottle, and place it on wax. If a cork
suspended by a silk thread (_f_) hang between these two wires, it will play
incessantly from one to the other, 'till the bottle is no longer
electrised; that is, it fetches and carries fire from the top to the bottom
of the bottle, 'till the equilibrium is restored.
EXPERIMENT IV.
FIG. 3. Place an electricised phial on wax; take a wire (_g_) in form of a
C, the ends at such a distance when bent, as that the upper may touch the
wire of the bottle, when the lower touches the bottom: stick the outer part
on a stick of sealing wax (_h_) which will serve as a handle. Then apply
the lower end to the bottom of the bottle, and gradually bring the
upper-end near the wire in the cork. The consequence is, spark follows
spark till the equilibrium is restored. Touch the top first, and on
approaching the bottom with the other end, you have a constant stream of
fire, from the wire entering the bottle. Touch the top and bottom together,
and the equilibrium will soon be restored, but silently and imperceptibly;
the crooked wire forming the communication.
EXPERIMENT V.
FIG. 4. Let a ring of thin lead or paper surround a bottle (_i_), even at
some distance from or above the bottom. From that ring let a wire proceed
up, 'till it touch the wire of the cork (_k_). A bottle so fixt cannot by
any means be electrised: the equilibrium is never destroyed: for while the
communication between the upper and lower parts of the bottle is continued
by the outside wire, the fire only circulates: what is driven out at
bottom, is constantly supply'd from the top. Hence a bottle cannot be
electrised that is foul or moist on the outside.
EXPERIMENT VI.
Place a man on a cake of wax, and present him the wire of the electrified
phial to touch, you standing on the floor, and holding it in your hand. As
often as he touches it, he will be electrified _plus_; and any one standing
on the floor may draw a spark from him. The fire in this experiment passes
out of the wire into him; and at the same time out of your hand into the
bottom of the bottle.
EXPERIMENT VII.
Give him the electrified phial to hold; and do you touch the wire; as often
you touch it he will be electrified _minus_, and may draw a spark from any
one standing on the floor. The fire now passes from the wire to you, and
from him into the bottom of the bottle.
EXPERIMENT VIII.
Lay two books on two glasses, back towards back, two or three Inches
distant. Set the electrified phial on one, and then touch the wire; that
book will be electrified _minus_; the electrical 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 electrised _plus_;
the fire passing into it from the wire, and the bottle at the same time
supply'd from your hand. A suspended small cork-ball will play between
these books 'till the equilibrium is restored.
EXPERIMENT IX.
When a body is electrised _plus_ it will repel an electrified feather or
small cork-ball. When _minus_ (or when in the common state) it will attract
them, but stronger when _minus_ than when in the common state, the
difference being greater.
EXPERIMENT X.
Tho', as in EXPER. VI. a man standing on wax may be electrised a number of
times, by repeatedly touching the wire of an electrised bottle (held in the
hand of one standing 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 strong spark, and is violently shock'd, no Electricity remains in him;
the fire only passing thro' him from the upper to the lower part of the
bottle. Observe, before the shock, to let some one on the floor touch him
to restore the equilibrium in his body; for in taking hold of the bottom of
the bottle, he sometimes becomes a little electrised _minus_, which will
continue after the shock; as would also any _plus_ Electricity, which he
might have given him before the shock. For, restoring the equilibrium in
the bottle does not at all affect the Electricity in the man thro' whom the
fire passes; that Electricity is neither increased nor diminish'd.
EXPERIMENT XI.
The passing of the electrical fire from the upper to the lower part of the
bottle, to restore the equilibrium is render'd strongly visible by the
following pretty experiment. Take a book whose cover is filletted with
gold; bend a wire of eight or ten inches long in the form of (_m_) FIG. 5,
slip it on the end of the cover of the book over the gold line, so as that
the shoulder of it may press upon one end of the gold line, the ring up,
but leaning towards the other end of the book. Lay the book on a glass or
wax; and on the other end of the gold lines, set the bottle electrised:
then bend the springing wire, by pressing it with a stick of wax till its
ring approaches the ring of the bottle wire; instantly there is a strong
spark and stroke, and the whole line of gold, which completes the
communication between the top and bottom of the bottle, will appear a vivid
flame, like the sharpest lightning. The closer the contact between the
shoulder of the wire, and the gold at one end of the line, and between the
bottom of the bottle and the gold at the other end, the better the
experiment succeeds. The room should be darkened. If you would have the
whole filletting round the cover appear in fire at once, let the bottle and
wire touch the gold in the diagonally opposite corners.
_I am_, &c.
B. FRANKLIN.
LETTER II.
FROM
Mr BENJ. FRANKLIN, in _Philadelphia_.
TO
Mr PETER COLLINSON, F.R.S. _London_.
_Sept. 1, 1747._
_SIR_,
In my last I informed you that, in pursuing our electrical enquiries, we
had observed some particular Phænomena, which we looked upon to be new, and
of which I promised to give you some account, tho' I apprehended they might
possibly not be new to you, as so many hands are daily employ'd in
electrical experiments on your side the water, some or other of which would
probably hit on the same observations.
The first is the wonderful effect of pointed bodies, both in _drawing off_
and _throwing off_ the electrical fire. For example:
Place an iron shot of three or four inches diameter, on the mouth of a
clean dry glass bottle. By a fine silken thread from the cieling, right
over the mouth of the bottle, suspend a small cork-ball, about the bigness
of a marble; the thread of such a length, as that the cork-ball may rest
against the side of the shot. Electrify the shot, and the ball will be
repelled to the distance of four or five inches, more or less, according to
the quantity of Electricity.--When in this state, if you present to the
shot the point of a long slender sharp bodkin, at six or eight inches
distance, the repellency is instantly destroy'd, and the cork flies to the
shot. A blunt body must be brought within an inch, and draw a spark, to
produce the same effect. To prove that the electrical fire is _drawn off_
by the point, if you take the blade of the bodkin out of the wooden handle,
and fix it in a stick of sealing wax, and then present it at the distance
aforesaid, or if you bring it very near, no such effect follows; but
sliding one finger along the wax till you touch the blade, and the ball
flies to the shot immediately.--If you present the point in the dark, you
will see, sometimes at a foot distance, and more, a light gather upon it
like that of a fire-fly or glow-worm; the less sharp the point, the nearer
you must bring it to observe the light; and at whatever distance you see
the light, you may draw off the electrical fire, and destroy the
repellency.--If a cork-ball so suspended be repelled by the tube, and a
point be presented quick to it, tho' at a considerable distance, 'tis
surprizing to see how suddenly it flies back to the tube. Points of wood
will do as well as those of iron, provided the wood is not dry; for
perfectly dry wood will no more conduct Electricity than sealing wax.
To shew that points will _throw off_ as well as _draw off_ the electrical
fire; lay a long sharp needle upon the shot, and you cannot electrise the
shot, so as to make it repel the cork-ball.--Or fix a needle to the end of
a suspended gun-barrel, or iron rod, so 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 electrised so as to give a spark, the
fire continually running out silently at the point. In the dark you may see
it make the same appearance as it does in the case beforementioned.
The repellency between the cork-ball and the shot is likewise destroy'd; 1.
By sifting fine sand on it; this does it gradually. 2. By breathing on it.
3. By making a smoke about it from burning wood.[1] 4. By candle light,
even tho' the candle is at a foot distance: these do it suddenly.--The
light of a bright coal from a wood fire; and the light of red-hot iron do
it likewise; but not at so great a distance. Smoke from dry rosin dropt on
hot iron, does not destroy the repellency; but is attracted by both shot
and cork-ball, forming proportionable atmospheres round them, making them
look beautifully, somewhat like some of the figures in _Burnet_'s or
_Whiston_'s theory of the earth.
_N. B._ This experiment should be made in a closet where the air is very
still.
The light of the sun thrown strongly on both cork and shot by a
looking-glass for a long time together, does not impair the repellency in
the least. This difference between fire-light and sun-light, is another
thing that seems new and extraordinary to us.
We had for some time been of opinion, that the electrical fire was not
created by friction, but collected, being really an element diffus'd among,
and attracted by other matter, particularly by water and metals. We had
even discovered and demonstrated its afflux to the electrical sphere, as
well as its efflux, by means of little light windmill wheels made of stiff
paper vanes, fixed obliquely and turning freely on fine wire axes. Also by
little wheels of the same matter, but formed like water wheels. Of the
disposition and application of which wheels, and the various phænomena
resulting, I could, if I had time, fill you a sheet. The impossibility of
electrising one's self (tho' standing on wax) by rubbing the tube and
drawing the fire from it; and the manner of doing it by passing the tube
near a person or thing standing on the floor, &c. had also occurred to us
some months before Mr _Watson_'s ingenious _Sequel_ came to hand, and these
were some of the new things I intended to have communicated to you.--But
now I need only mention some particulars not hinted in that piece, with our
reasonings thereupon; though perhaps the latter might well enough be
spared.
1. A person standing on wax, and rubbing the tube, and another person on
wax drawing the fire; they will both of them, (provided they do not stand
so as to touch one another) appear to be electrised, to a person standing
on the floor; that is, he will perceive a spark on approaching each of them
with his knuckle.
2. But if the persons on wax touch one another during the exciting of the
tube, neither of them will appear to be electrised.
3. If they touch one another after exciting the tube, and drawing the fire
as aforesaid, there will be a stronger spark between them, than was between
either of them and the person on the floor.
4. After such strong spark, neither of them discover any electricity.
These appearances we attempt to account for thus. We suppose as aforesaid,
that electrical fire is a common element, of which every one of the three
persons abovementioned has his equal share, before any operation is begun
with the Tube. _A_, who stands on wax and rubs the tube collects the
electrical fire from himself into the glass; and his communication with the
common stock being cut off by the wax, his body is not again immediately
supply'd. _B_, (who stands on wax likewise) passing his knuckle along near
the tube, receives the fire which was collected by the glass from _A_; and
his communication with the common stock being likewise cut off, he retains
the additional quantity received.--To _C_, standing on the floor, both
appear to be electrised: for he having only the middle quantity of
electrical fire, receives a spark upon approaching _B_, who has an over
quantity; but gives one to _A_, who has an under quantity. If _A_ and _B_
approach to touch each other, the spark is stronger, because the difference
between them is greater; after such touch there is no spark between either
of them and _C_, because the electrical fire in all is reduced to the
original equality. If they touch while electrising, the equality is never
destroy'd, the fire only circulating. Hence have arisen some new terms
among us: we say, _B_, (and bodies like circumstanced) is electrised
_positively_; _A_, _negatively_. Or rather, _B_ is electrised _plus_; _A_,
_minus_. And we daily in our experiments electrise bodies _plus_ or _minus_
as we think proper.--To electrise _plus_ or _minus_, no more needs to be
known than this, that the parts of the tube or sphere that are rubbed, do,
in the instant of the friction attract the electrical fire, and therefore
take it from the thing rubbing: the same parts immediately, as the friction
upon them ceases, are disposed to give the fire they have received, to any
body that has less. Thus you may circulate it, as Mr _Watson_ has shewn;
you may also accumulate or substract it upon or from any body, as you
connect that body with the rubber or with the receiver, the communication
with the common stock being cut off. We think that ingenious gentleman was
deceived, when he imagined (in his _Sequel_) that the electrical fire came
down the wire from the cieling to the gun-barrel, thence to the sphere, and
so electrised the machine and the man turning the wheel, _&c._ We suppose
it was _driven off_, and not brought on thro' that wire; and that the
machine and man, _&c._ were electrised _minus_; _i. e._ had less electrical
fire in them than things in common.
As the vessel is just upon sailing, I cannot give you so large an account
of American Electricity as I intended: I shall only mention a few
particulars more.--We find granulated lead better to fill the phial with,
than water, being easily warmed, and keeping warm and dry in damp air.--We
fire spirits with the wire of the phial.--We light candles, just blown out,
by drawing a spark among the smoke between the wire and snuffers.--We
represent lightning, by passing the wire in the dark over a china plate
that has gilt flowers, or applying it to gilt frames of looking-glasses,
_&c._--We electrise a person twenty or more times running, with a touch of
the finger on the wire, thus: He stands on wax. Give him the electrised
bottle in his hand. Touch the wire with your finger, and then touch his
hand or face; there are sparks every time.--We encrease the force of the
electrical kiss vastly, thus: Let _A_ and _B_ stand on wax; give one of
them the electrised phial in hand; let the other take hold of the wire;
there will be a small spark; but when their lips approach, they will be
struck and shock'd. The same if another gentleman and lady, _C_ and _D_,
standing also on wax, and joining hands with _A_ and _B_, salute, or shake
hands.--We suspend by fine silk thread a counterfeit spider, made of a
small piece of burnt cork, with legs of linnen thread, and a grain or two
of lead stuck in him to give him more weight. Upon the table, over which he
hangs, we stick a wire upright as high as the phial and wire, two or three
inches from the spider; then we animate him by setting the electrified
phial at the same distance on the other side of him; he will immediately
fly to the wire of the phial, bend his legs in touching it, then spring
off, and fly to the wire in the table; thence again to the wire of the
phial, playing with his legs against both in a very entertaining manner,
appearing perfectly alive to persons unacquainted. He will continue this
motion an hour or more in dry weather.--We 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
flash of lightning: not upon the leather, nor, if you touch the leather
instead of the gold. We rub our tubes with buckskin, and observe always to
keep the same side to the tube, and never to sully the tube by handling;
thus they work readily and easily, without the least fatigue; especially if
kept in tight pastboard cases, lined with flannel, and fitting closeto the
tube.[2]--This I mention because the _European_ papers, on Electricity,
frequently speak of rubbing the tube, as a fatiguing exercise. Our spheres
are fixed on iron axes, which pass through them. At one end of the axis
there is a small handle, with which we turn the sphere like a common
grindstone. This we find very commodious, as the machine takes up but
little room, is portable, and may be enclosed in a tight box, when not in
use. 'Tis true, the sphere does not turn so swift, as when the great wheel
is used: but swiftness we think of little importance, since a few turns
will charge the phial, _&c._ sufficiently.
_I am_, &c.
B. FRANKLIN.
[Illustration]
LETTER III.
FROM
Mr BENJ. FRANKLIN, in _Philadelphia_.
TO
Mr PETER COLLINSON, F.R.S. _London_.
_Farther_ EXPERIMENTS _and_ OBSERVATIONS _in_ ELECTRICITY.
_1748._
_SIR_,
§ 1. There will be the same explosion and shock, 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 charg'd phial safely by the hook, and not at the same time
diminish its force, it must first be set down on an electric _per se_.
3. The phial will be electrified as strongly, if held by the hook, and the
coating apply'd to the globe or tube; as when held by the coating, and the
hook apply'd.
4. But the _direction_ of the electrical fire being different in the
charging, will also be different in the explosion. The bottle charged thro'
the hook, will be discharged thro' the hook; the bottle charged thro' the
coating, will be discharged thro' the coating, and not other ways: for the
fire must come out the same 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 spark or
shock will follow; because each hook is disposed to give fire, and neither
to receive it. Set one of the bottles down on glass, take it up by the
hook, and apply its coating to the hook of the other; then there will be an
explosion and shock, and both bottles will be discharged.
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 first to the coating of the other, and there will be
no shock or spark. Set that down on glass which you held by the hook, take
it up by the coating, and bring the two hooks together: a spark and shock
will follow, and both phials be discharged.
In this experiment the bottles are totally discharged, or the equilibrium
within them restored. The _abounding_ of fire in one of the hooks (or
rather in the internal surface of one bottle) being exactly equal to the
_wanting_ of the other: and therefore, as each bottle has in itself the
_abounding_ as well as the _wanting_, the wanting and abounding must be
equal in each bottle. See §. 8, 9, 10, 11. But if a man holds in his hands
two bottles, one fully electrify'd, the other not at all, and brings their
hooks together, he has but half a shock, and the bottles will both remain
half electrified, the one being half discharged, and the other half
charged.
7. Place two phials equally charged on a table at five or six inches
distance. Let a cork-ball, suspended by a silk thread, hang between them.
If the phials were both charged through their hooks, the cork, when it has
been attracted and repell'd by the one, will not be attracted, but equally
repelled by the other. But if the phials were charged, the one through the
hook, and the other[3] through the coating, the ball, when it is repelled
from one hook, will be as strongly attracted by the other, and play
vigorously between them, 'till both phials are nearly discharged.
8. When we use the terms of _charging_ and _discharging_ the phial, 'tis in
compliance with custom, and for want of others more suitable. Since we are
of opinion, that there is really no more electrical fire in the phial after
what is called its _charging_, than before, nor less after its
_discharging_; excepting only the small spark that might be given to, and
taken from, the non-electric matter, if separated from the bottle, which
spark may not be equal to a five hundredth part of what is called the
explosion.
For if, on the explosion, the electrical fire came out of the bottle by one
part, and did not enter in again by another; then, if a man standing on
wax, and holding the bottle in one hand, takes the spark by touching the
wire hook with the other, the bottle being thereby _discharged_, the man
would be _charged_; or whatever fire was lost by one, would be found in the
other, since there is no way for its escape: But the contrary is true.
9. Besides the phial will not suffer what is called a _charging_, unless as
much fire can go out of it one way, as is thrown in by another. A phial
cannot be charged standing on wax or glass, or hanging on the prime
conductor, unless a communication be form'd between its coating and the
floor.
10. But suspend two or more phials on the prime conductor, one hanging to
the tail of the other; and a wire from the last to the floor, an equal
number of turns of the wheel shall charge them all equally, and every one
as much as one alone would have been. What is driven out at the tail of the
first, serving to charge the second; what is driven out of the second
charging the third; and so on. By this means a great number of bottles
might be charged with the same labour, and equally high, with one alone,
were it not that every bottle receives new fire, and loses its old with
some reluctance, or rather gives some small resistance to the charging,
which in a number of bottles becomes more equal to the charging power, and
so repels the fire back again on the globe, sooner than a single bottle
would do.
11. When a bottle is charged in the common way, its _inside_ and _outside_
surfaces stand ready, the one to give fire by the hook, the other to
receive it by the coating; the one is full, and ready to throw out, the
other empty and extremely hungry; yet as the first will not _give out_,
unless the other can at the same instant _receive in_; so neither will the
latter receive in, unless the first can at the same instant give out. When
both can be done at once, 'tis done with inconceivable quickness and
violence.
12. So a strait spring (tho' the comparison does not agree in every
particular) when forcibly bent, must, to restore itself, contract that side
which in the bending was extended, and extend that which was contracted; if
either of these two operations be hindered, the other cannot be done. But
the spring is not said to be _charg'd_ with elasticity when bent, and
discharg'd when unbent; its quantity of elasticity is always the same.
13. Glass, in like manner, has, within its substance, always the same
quantity of electrical fire, and that a very great quantity in proportion
to the mass of glass, as shall be shewn hereafter.
14. This quantity, proportioned to the glass, it strongly and obstinately
retains, and will have neither more nor less, though it will suffer a
change to be made in its parts and situation; _i. e._ we may take away part
of it from one of the sides, provided we throw an equal quantity into the
other.
15. Yet when the situation of the electrical fire is thus altered in the
glass; when some has been taken from one side, and some added to the other,
it will not be at rest or in its natural state, till 'tis restored to its
original equality.--And this restitution cannot be made through the
substance of the glass, but must be done by a non-electric communication
formed without, from surface to surface.
16. Thus, the whole force of the bottle, and power of giving a shock, is in
the GLASS ITSELF; the non-electrics in contact with the two surfaces,
serving only to _give_ and _receive_ to and from the several parts of the
glass; that is, to give on one side, and take away from the other.
17. This was discovered here in the following manner. Purposing to analyse
the electrified bottle, in order to find wherein its strength lay, we
placed it on glass, and drew out the cork and wire which for that purpose
had been loosely put in. Then taking the bottle in one hand, and bringing a
finger of the other near its mouth, a strong spark came from the water, and
the shock was as violent as if the wire had remained in it, which shewed
that the force did not lie in the wire. Then to find if it resided in the
water, being crouded into and condensed in it, as connfi'd by the glass,
which had been our former opinion, we electrify'd the bottle again, and
placing it on glass, drew out the wire and cork as before; then taking up
the bottle we decanted all its water into an empty bottle, which likewise
stood on glass; and taking up that other bottle, we expected if the force
resided in the water, to find a shock from it; but there was none. We
judged then, that it must either be lost in decanting, or remain in the
first bottle. The latter we found to be true: for that bottle on trial gave
the shock, though filled up as it stood with fresh unelectrified water from
a tea-pot.--To find then, whether glass had this property merely as glass,
or whether the form contributed any thing to it; we took a pane of
sash-glass, and laying it on the stand, placed a plate of lead on its upper
surface; then electrify'd that plate, and bringing a finger to it, there
was a spark and shock. We then took two plates of lead of equal dimensions,
but less than the glass by two inches every way, and electrified the glass
between them, by electrifying the uppermost lead; then separated the glass
from the lead, in doing which, what little fire might be in the lead was
taken out and the glass being touched in the electrified parts with a
finger, afforded only very small pricking sparks, but a great number of
them might be taken from different places. Then dexterously placing it
again between the leaden plates, and compleating a circle between the two
surfaces, a violent shock ensued.--Which demonstrated the power to reside
in glass as glass, and that the non-electrics in contact served only, like
the armature of a loadstone, to unite the force of the several parts, and
bring them at once to any point desired: it being a property of a
non-electric, that the whole body instantly receives or gives what
electrical fire is given to or taken from any one of its parts.
18. Upon this, we made what we call'd an _electrical-battery_, consisting
of eleven panes of large sash-glass, arm'd with thin leaden plates pasted
on each side, placed vertically, and supported at two inches distance on
silk cords, with thick hooks of leaden wire, one from each side, standing
upright, distant from each other, and convenient communications of wire and
chain, from the giving side of one pane, to the receiving side of the
other; that so the whole might be charged together, and with the same
labour as one single pane; and another contrivance to bring the giving
sides, after charging, in contact with one long wire, and the receivers
with another, which two long wires would give the force of all the plates
of glass at once through the body of any animal forming the circle with
them. The plates may also be discharged separately, or any number together
that is required. But this machine is not much used, as not perfectly
answering our intention with regard to the ease of charging, for the reason
given § 10. We made also of large glass panes, magical pictures, and
self-moving animated wheels, presently to be described.
19. I perceive by the ingenious Mr _Watson_'s last book, lately received,
that Dr _Bevis_ had used, before we had, panes of glass to give a shock;
though, till that book came to hand, I thought to have communicated it to
you as a novelty. The excuse for mentioning it here, is, that we tried the
experiment differently, drew different consequences from it, (for Mr
_Watson_ still seems to think the fire _accumulated on the non-electric_
that is in contact with the glass, page 72) and, as far as we hitherto
know, have carried it farther.
20. The magical picture is made thus. Having a large metzotinto with a
frame and glass, suppose of the KING, (God preserve him) take out the
print, and cut a pannel out of it, near two inches distant from the frame
all round. If the cut is through the picture 'tis not the worse. With thin
paste or gum-water, fix the border that is cut off on the inside of the
glass, pressing it smooth and close; then fill up the vacancy by gilding
the glass well with leaf gold or brass. Gild likewise the inner edge of the
back of the frame all round except the top part, and form a communication
between that gilding and the gilding behind the glass: then put in the
board, and that side is finished. Turn up the glass, and gild the fore side
exactly over the back gilding, and when it is dry, cover it by pasting on
the pannel of the picture that had been cut out, observing to bring the
corresponding parts of the border and picture together, by which the
picture will appear of a piece as at first, only part is behind the glass,
and part before.--Hold the picture horizontally by the top, and place a
little moveable gilt crown on the king's-head. If now the picture be
moderately electrified, and another person take hold of the frame with one
hand, so that his fingers touch its inside gilding, and with the other hand
endeavour to take off the crown, he will receive a terrible blow, and fail
in the attempt. If the picture were highly charged, the consequence might
perhaps be as fatal as that of high-treason; for when the spark is taken
through a quire of paper laid on the picture, by means of a wire
communication, it makes a fair hole through every sheet, that is, through
48 leaves, (though a quire of paper is thought good armour against the push
of a sword or even against a pistol bullet) and the crack is exceeding
loud. The operator, who holds the picture by the upper-end, where the
inside of the frame is not gilt, to prevent its falling, feels nothing of
the shock, and may touch the face of the picture without danger, which he
pretends is a test of his loyalty.--If a ring of persons take the shock
among them, the experiment is called, _The Conspirators_.
21. On the principle, in § 7, that hooks of bottles, differently charged,
will attract and repel differently, is made, an electrical wheel, that
turns with considerable strength. A small upright shaft of wood passes at
right angles through a thin round board, of about twelve inches diameter,
and turns on a sharp point of iron fixed in the lower end, while a strong
wire in the upper-end passing thro' a small hole in a thin brass plate,
keeps the shaft truly vertical. About thirty _radii_ of equal length, made
of sash glass cut in narrow strips, issue horizontally from the
circumference of the board, the ends most distant from the center being
about four inches apart. On the end of every one, a brass thimble is fixed.
If now the wire of a bottle electrified in the common way, be brought near
the circumference of this wheel, it will attract the nearest thimble, and
so put the wheel in motion; that thimble, in passing by, receives a spark,
and thereby being electrified is repelled and so driven forwards; while a
second being attracted, approaches the wire, receives a spark, and is
driven after the first, and so on till the wheel has gone once round, when
the thimbles before electrified approaching the wire, instead of being
attracted as they were at first, are repelled, and the motion presently
ceases.--But if another bottle which had been charged through the coating
be placed near the same wheel, its wire will attract the thimble repelled
by the first, 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 first bottle, but even robbing them of their natural quantity,
instead of being repelled when they come again towards the first bottle,
they are more strongly attracted, so that the wheel mends its pace, till it
goes with great rapidity twelve or fifteen rounds in a minute, and with
such strength, as that the weight of one hundred _Spanish_ dollars with
which we once loaded it, did not seem in the least to retard its
motion.--This is called an electrical jack; and if a large fowl were
spitted on the upright shaft, it would be carried round before a fire with
a motion fit for roasting.
22. But this wheel, like those driven by wind, water, or weights, moves by
a foreign force, to wit, that of the bottles. The self-moving wheel, though
constructed on the same principles, appears more surprising. 'Tis made of a
thin round plate of window-glass, seventeen inches diameter, well gilt on
both sides, all but two inches next the edge. Two small hemispheres of wood
are then fixed with cement to the middle of the upper and under sides,
centrally opposite, and in each of them a thick strong 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 rests on a bit
of brass cemented within a glass salt-celler. The upper end of its axis
passes thro' a hole in a thin brass plate cemented to a long strong piece
of glass, which keeps it six or eight inches distant from any non-electric,
and has a small ball of wax or metal on its top to keep in the fire. In a
circle on the table which supports the wheel, are fixed twelve small
pillars of glass, at about four inches distance, with a thimble on the top
of each. On the edge of the wheel is a small leaden bullet communicating by
a wire with the gilding of the _upper_ surface of the wheel; and about six
inches from it is another bullet communicating in like manner with the
_under_ surface. When the wheel is to be charged by the upper surface, a
communication must be made from the under surface to the table. When it is
well charg'd it begins to move; the bullet nearest to a pillar moves
towards the thimble on that pillar, and passing by electrifies it and then
pushes itself from it; the succeeding bullet, which communicates with the
other surface of the glass, more strongly attracts that thimble on account
of its being before electrified by the other bullet; and thus the wheel
encreases its motion till it comes to such a height as that the resistance
of the air regulates it. It will go half an hour, and make one minute with
another twenty turns in a minute, which is six hundred turns in the whole;
the bullet of the upper surface giving in each turn twelve sparks, to the
thimbles, which make seven thousand two hundred sparks; and the bullet of
the under surface receiving as many from the thimbles; those bullets moving
in the time near two thousand five hundred feet.--The thimbles are well
fixed, and in so exact a circle, that the bullets may pass within a very
small distance of each of them.--If instead of two bullets you put eight,
four communicating with the upper surface, and four with the under surface,
placed alternately; which eight, at about six inches distance, compleats
the circumference, the force and swiftness will be greatly increased, the
wheel making fifty turns in a minute; but then it will not continue moving
so long.--These wheels may be applied, perhaps, to the ringing of chimes,
and moving of light-made Orreries.
23. A small wire bent circularly with a loop at each end; let one end rest
against the under surface of the wheel, and bring the other end near the
upper surface, it will give a terrible crack, and the force will be
discharged.
24. Every spark in that manner drawn from the surface of the wheel, makes a
round hole in the gilding, tearing off a part of it in coming out; which
shews that the fire is not accumulated on the gilding, but is in the glass
itself.
25. The gilding being varnish'd over with turpentine varnish, the varnish
tho' dry and hard, is burnt by the spark drawn thro' it, and gives a strong
smell and visible smoke. And when the spark is drawn through paper, all
round the hole made by it, the paper will be blacked by the smoke, which
sometimes penetrates several of the leaves. Part of the gilding torn off,
is also found forcibly driven into the hole made in the paper by the
stroke.
26. 'Tis amazing to observe in how small a portion of glass a great
electrical force may lie. A thin glass bubble, about an inch diameter,
weighing only six grains, being half-filled with water, partly gilt on the
outside, and furnish'd with a wire hook, gives, when electrified, as great
a shock as a man can well bear. As the glass is thickest near the orifice,
I suppose the lower half, which being gilt was electrified, and gave the
shock, did not exceed two grains; for it appeared, when broke, much thinner
than the upper half.--If one of these thin bottles be electrified by the
coating, and the spark taken out thro' the gilding, it will break the glass
inwards at the same time that it breaks the gilding outwards.
27. And allowing (for the reasons before given, § 8, 9, 10,) that there is
no more electrical fire in a bottle after charging, than before, how great
must be the quantity in this small portion of glass! It seems as if it were
of its very substance and essence. Perhaps if that due quantity of
electrical fire so obstinately retained by glass, could be separated from
it, it would no longer be glass; it might lose its transparency, or its
brittleness, or its elasticity.--Experiments may possibly be invented
hereafter, to discover this.