0569
0569f
Experiments and Observations on Electricity
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.
27. We are surprized at the account given in Mr _Watson_'s book, of a shock
communicated through a great space of dry ground, and suspect there must be
some metaline quality in the gravel of that ground; having found that
simple dry earth, rammed in a glass tube, open at both ends, and a wire
hook inserted in the earth at each end, the earth and wires making part of
a circle, would not conduct the least perceptible shock, and indeed when
one wire was electrify'd, the other hardly showed any signs of its being in
connection with it.--Even a thoroughly wet pack-thread sometimes fails of
conducting a shock, tho' it otherwise conducts electricity very well. A dry
cake of ice, or an icicle held between two in a circle, likewise prevents
the shock; which one would not expect, as water conducts it so perfectly
well.--Gilding on a new book, though at first it conducts the shock
extremely well, yet fails after ten or a dozen experiments, though it
appears otherwise in all respects the same, which we cannot account for.
28. There is one experiment more which surprizes us, and is not hitherto
satisfactorily accounted for; it is this. Place an iron shot on a glass
stand, and let a ball of damp cork, suspended by a silk thread, hang in
contact with the shot. Take a bottle in each hand, one that is electrify'd
through the hook, the other through the coating: Apply the giving wire to
the shot, which will electrify it _positively_, and the cork shall be
repelled: Then apply the requiring wire, which will take out the spark
given by the other; when the cork will return to the shot: Apply the same
again, and take out another spark, so will the shot be electrify'd
_negatively_; and the cork in that case shall be repelled equally as
before. Then apply the giving wire to the shot, and give the spark it
wanted, so will the cork return: Give it another, which will be an addition
to its natural quantity, so will the cork be repelled again: And so may the
experiment be repeated as long as there is any charge in the bottles. Which
shews that bodies having less than the common quantity of Electricity,
repel each other, as well as those that have more.
Chagrined a little that we have hitherto been able to produce nothing in
this way of use to mankind; and the hot weather coming on, when electrical
experiments are not so agreeable, 'tis proposed to put an end to them for
this season, somewhat humorously, in a party of pleasure, on the banks of
_Skuylkill_.[4] Spirits, at the same time, are to be fired by a spark sent
from side to side through the river, without any other conductor than the
water; an experiment which we some time since performed, to the amazement
of many. A turkey is to be killed for our dinner by the _electrical shock_,
and roasted by the _electrical jack_, before a fire kindled by the
_electrified bottle_; when the healths of all the famous electricians in
_England_, _Holland_, _France_, and _Germany_, are to be drank in
[5]_electrified bumpers_, under the discharge of guns from the _electrical
battery_.
_April 29,
1749._
[Illustration]
LETTER IV.
CONTAINING
OBSERVATIONS _and_ SUPPOSITIONS, _towards forming a new_ HYPOTHESIS, _for
explaining the several_ Phænomena _of_ THUNDER-GUSTS.[6]
_SIR_,
§. 1. Non-electric bodies, that have electric fire thrown into them, will
retain it 'till other non-electrics, that have less, approach; and then
'tis communicated by a snap, and becomes equally divided.
2. Electrical fire loves water, is strongly attracted by it, and they can
subsist together.
3. Air is an electric _per se_, and when dry will not conduct the
electrical fire; it will neither receive it, nor give it to other bodies;
otherwise no body surrounded by air could be electrified positively and
negatively: for should it be attempted positively, the air would
immediately take away the overplus; or negatively, the air would supply
what was wanting.
4. Water being electrified, the vapours arising from it will be equally
electrified; and floating in the air, in the form of clouds, or otherwise,
will retain that quantity of electrical fire, till they meet with other
clouds or bodies not so much electrified, and then will communicate as
beforementioned.
5. Every particle of matter electrified is repelled by every other particle
equally electrified. Thus the stream of a fountain, naturally dense and
continual, when electrified, will separate and spread in the form of a
brush, every drop endeavouring to recede from every other drop. But on
taking out the electrical fire, they close again.
6. Water being strongly electrified (as well as when heated by common fire)
rises in vapours more copiously; the attraction of cohesion among its
particles being greatly weakened, by the opposite power of repulsion
introduced with the electrical fire; and when any particle is by any means
disengaged, 'tis immediately repelled, and so flies into the air.
7. Particles happening to be situated as _A_ and _B_, are more easily
disengaged than _C_ and _D_, as each is held by contact with three only,
whereas _C_ and _D_ are each in contact with nine. When the surface of
water has the least motion, particles are continually pushed into the
situation represented by FIG. 6.
8. Friction between a non-electric and an electric _per se_, will produce
electrical fire; not by _creating_, but _collecting_ it: for it is equally
diffused in our walls, floors, earth, and the whole mass of common matter.
Thus the whirling glass globe, during its friction against the cushion,
draws fire from the cushion, the cushion is supplied from the frame of the
machine, that from the floor on which it stands. Cut off the communication
by thick glass or wax placed under the cushion, and no fire can be
_produced_, because it cannot be _collected_.
9. The Ocean is a compound of water, a non-electric, and salt an electric
_per se_.
10. When there is a friction among the parts near its surface, the
electrical fire is collected from the parts below. It is then plainly
visible in the night; it appears at the stern and in the wake of every
sailing vessel; every dash of an oar shows it, and every surff and spray:
in storms the whole sea seems on fire.--The detach'd particles of water
then repelled from the electrified surface, continually carry off the fire
as it is collected; they rise, and form clouds, and those clouds are highly
electrified, and retain the fire 'till they have an opportunity of
communicating it.
11. The particles of water rising in vapours, attach themselves to
particles of air.
12. The particles of air are said to be hard, round, separate and distant
from each other; every particle strongly repelling every other particle,
whereby they recede from each other, as far as common gravity will permit.
13. The space between any three particles equally repelling each other,
will be an equilateral triangle.
14. In air compressed, these triangles are smaller; in rarified Air they
are larger.
15. Common fire joined with air, increases the repulsion, enlarges the
triangles, and thereby makes the air specifically lighter. Such Air among
denser air, will rise.
16. Common fire, as well as electrical fire gives repulsion to the
particles of water, and destroys their attraction of cohesion; hence common
fire, as well as electrical fire, assists in raising vapours.
17. Particles of water, having no fire in them, mutually attract each
other. Three particles of water then being attached to the three particles
of a triangle of air, would by their mutual attraction operating against
the air's repulsion, shorten the sides and lessen the triangle, whereby
that portion of air being made denser, would sink to the earth with its
water, and not rise to contribute to the formation of a cloud.
18. But if every particle of water attaching itself to air, brings with it
a particle of common fire, the repulsion of the air being assisted and
strengthened by the fire, more than obstructed by the mutual attraction of
the particles of water, the triangle dilates, and that portion of air
becoming rarer and specifically lighter rises.
19. If the particles of water bring electrical fire when they attach
themselves to air, the repulsion between the particles of water
electrified, joins with the natural repulsion of the air, to force its
particles to a greater distance, whereby the triangles are dilated, and the
air rises, carrying up with it the water.
20. If the particles of water bring with them portions of _both sorts_ of
fire, the repulsions of the particles of air is still more strengthened and
increased, and the triangles farther enlarged.
21. One particle of air may be surrounded by twelve particles of water of
equal size with itself, all in contact with it; and by more added to those.
22. Particles of air thus loaded would be drawn nearer together by the
mutual attraction of the particles of water, did not the fire, common or
electrical, assist their repulsion.
23. If air thus loaded be compressed by adverse winds, or by being driven
against mountains, &c. or condensed by taking away the fire that assisted
it in expanding; the triangles contract, the air with its water will
descend as a dew; or, if the water surrounding one particle of air comes in
contact with the water surrounding another, they coalesce and form a drop,
and we have rain.
24. The sun supplies (or seems to supply) common fire to all vapours,
whether raised from earth or sea.
25. Those vapours which have both common and electrical fire in them, are
better supported, than those which have only common fire in them. For when
vapours rise into the coldest region above the earth, the cold will not
diminish the electrical fire, if it doth the common.
26. Hence clouds formed by vapours raised from fresh waters within land,
from growing vegetables, moist earth, &c. more speedily and easily deposite
their water, having but little electrical fire to repel and keep the
particles separate. So that the greatest part of the water raised from the
land is let fall on the land again; and winds blowing from the land to the
sea are dry; there being little use for rain on the sea, and to rob the
land of its moisture, in order to rain on the sea, would not appear
reasonable.
27. But clouds formed by vapours raised from the sea, having both fires,
and particularly a great quantity of the electrical, support their water
strongly, raise it high, and being moved by winds may bring it over the
middle of the broadest continent from the middle of the widest ocean.
28. How these ocean clouds, so strongly supporting their water, are made to
deposite it on the land where 'tis wanted, is next to be considered.
29. If they are driven by winds against mountains, those mountains being
less electrified attract them, and on contact take away their electrical
fire (and being cold, the common fire also;) hence the particles close
towards the mountains and towards each other. If the air was not much
loaded, it only falls in dews on the mountain tops and sides, forms
springs, and descends to the vales in rivulets, which united make larger
streams and rivers. If much loaded, the electrical fire is at once taken
from the whole cloud; and, in leaving it, flashes brightly and cracks
loudly; the particles instantly coalescing for want of that fire, and
falling in a heavy shower.
30. When a ridge of mountains thus dams the clouds, and draws the
electrical fire from the cloud first approaching it; that which next
follows, when it comes near the first cloud, now deprived of its fire,
flashes into it, and begins to deposite its own water; the first cloud
again flashing into the mountains; the third approaching cloud, and all the
succeeding ones, acting in the same manner as far back as they extend,
which may be over many hundred miles of country.
31. Hence the continual storms of rain, thunder, and lightning on the
east-side of the _Andes_, which running north and south, and being vastly
high, intercept all the clouds brought against them from the _Atlantic_
ocean by the trade winds, and oblige them to deposite their waters, by
which the vast rivers _Amazons_, _La Plata_, and _Oroonoko_ are formed,
which return the water into the same sea, after having fertilized a country
of very great extent.
32. If a country be plain, having no mountains to intercept the electrified
clouds, yet is it not without means to make them deposite their water. For
if an electrified cloud coming from the sea, meets in the air a cloud
raised from the land, and therefore not electrified; the first will flash
its fire into the latter, and thereby both clouds shall be made suddenly to
deposite water.
33. The electrified particles of the first cloud close when they lose their
fire; the particles of the other cloud close in receiving it: in both, they
have thereby an opportunity of coalescing into drops.--The concussion or
jerk given to the air, contributes also to shake down the water, not only
from those two clouds but from others near them. Hence the sudden fall of
rain immediately after flashes of lightning.
34. To shew this by an easy experiment. Take two round pieces of pasteboard
two inches diameter; from the center and circumference of each of them
suspend by fine silk threads eighteen inches long, seven small balls of
wood, or seven peas equal in bigness; so will the balls appending to each
pasteboard, form equal equilateral triangles, one ball being in the center,
and six at equal distances from that, and from each other; and thus they
represent particles of air. Dip both sets in water, and some cohering to
each ball they will represent air loaded. Dexterously electrify one set,
and its balls will repel each other to a greater distance, enlarging the
triangles. Could the water supported by the seven balls come into contact,
it would form a drop or drops so heavy as to break the cohesion it had with
the balls, and so fall.--Let the two sets then represent two clouds, the
one a sea cloud electrified, the other a land cloud. Bring them within the
sphere of attraction, and they will draw towards each other, and you will
see the separated balls close thus; the first electrified ball that comes
near an unelectrified ball by attraction joins it, and gives it fire;
instantly they separate, and each flies to another ball of its own party,
one to give, the other to receive fire; and so it proceeds through both
sets, but so quick as to be in a manner instantaneous. In the collision
they shake off and drop their water, which represents rain.
35. Thus when sea and land clouds would pass at too great a distance for
the flash, they are attracted towards each other till within that distance;
for the sphere of electrical attraction is far beyond the distance of
flashing.
36. When a great number of clouds from the sea meet a number of clouds
raised from the land, the electrical flashes appear to strike in different
parts; and as the clouds are jostled and mixed by the winds, or brought
near by the electrical attraction, they continue to give and receive flash
after flash, till the electrical fire is equally diffused.
37. When the gun-barrel (in electrical experiments) has but little
electrical fire in it, you must approach it very near with your knuckle,
before you can draw a spark. Give it more fire, and it will give a spark at
a greater distance. Two gun-barrels united, and as highly electrified, will
give a spark at a still greater distance. But if two gun-barrels
electrified will strike at two inches distance, and make a loud snap, to
what a great distance may 10,000 acres of electrified cloud strike and give
its fire, and how loud must be that crack!
38. It is a common thing to see clouds at different heights passing
different ways, which shews different currents of air, one under the other.
As the air between the tropics is rarified by the sun, it rises, the denser
northern and southern air pressing into its place. The air so rarified and
forced up, passes northward and southward, and must descend 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, pass different ways, 'tis
easy to conceive how the clouds, passing over each other, may attract each
other, and so come near enough for the electrical stroke. And also how
electrical clouds may be carried within land very far from the sea, before
they have an opportunity to strike.
40. When the air, with its vapours raised from the ocean between the
tropics, comes to descend in the polar regions, and to be in contact with
the vapours arising there, the electrical fire they brought begins to be
communicated, and is seen in clear nights, being first visible where 'tis
first in motion, that is, where the contact begins, or in the most northern
part; from thence the streams of light seem to shoot southerly, even up to
the zenith of northern countries. But tho' the light seems to shoot from
the north southerly, the progress of the fire is really from the south
northerly, its motion beginning in the north being the reason that 'tis
there first seen.
For the electrical fire is never visible but when in motion, and leaping
from body to body, or from particle to particle thro' the air. When it
passes thro' dense bodies 'tis unseen. When a wire makes part of the
circle, in the explosion of the electrical phial, the fire, though in great
quantity, passes in the wire invisibly: but in passing along a chain, it
becomes visible as it leaps from link to link. In passing along
leaf-gilding 'tis visible: for the leaf-gold is full of pores; hold a leaf
to the light and it appears like a net; and the fire is seen in its leaping
over the vacancies.--And as when a long canal filled with still water is
opened at one end, in order to be discharged, the motion of the water
begins first near the opened end, and proceeds towards the close end, tho'
the water itself moves from the close towards the opened end: so the
electrical fire discharged into the polar regions, perhaps from a thousand
leagues length of vaporiz'd air, appears first where 'tis first in motion,
_i. e._ in the most northern part, and the appearance proceeds southward,
tho' the fire really moves northward. This is supposed to account for the
_Aurora Borealis_.
41. When there is great heat on the land, in a particular region (the sun
having shone on it perhaps several days, while the surrounding countries
have been screen'd by clouds) the lower air is rarified and rises, the
cooler denser air above descends; the clouds in that air meet from all
sides, and join over the heated place; and if some are electrified, others
not, lightning and thunder succeed, and showers fall. Hence thunder-gusts
after heats, and cool air after gusts; the water and the clouds that bring
it, coming from a higher and therefore a cooler region.
42. An electrical spark, drawn from an irregular body at some distance is
scarce ever strait, but shows crooked and waving in the air. So do the
flashes of lightning; the clouds being very irregular bodies.
43. As electrified clouds pass over a country, high hills and high trees,
lofty towers, spires, masts of ships, chimneys, _&c._ as so many
prominencies and points, draw the electrical fire, and the whole cloud
discharges there.
44. Dangerous, therefore, is it to take shelter under a tree during a
thunder-gust. It has been fatal to many, both men and beasts.
45. It is safer to be in the open field for another reason. When the
clothes are wet, if a flash in its way to the ground should strike your
head, it will run in the water over the surface 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 electrical bottle, when a
dry rat may.
46. Common fire is in all bodies, more or less, as well as electrical fire.
Perhaps they may be different modifications of the same element; or they
may be different elements. The latter is by some suspected.
47. If they are different things, yet they may and do subsist together in
the same body.
48. When electrical fire strikes thro' a body, it acts upon the common fire
contained in it, and puts that fire in motion; and if there be a sufficient
quantity of each kind of fire, the body will be inflamed.
49. When the quantity of common fire in the body is small, the quantity of
the electrical fire (or the electrical stroke) should be greater: if the
quantity of common fire be great, less electrical fire suffices to produce
the effect.
50. Thus spirits must be heated before we can fire them by the electrical
spark. If they are much heated a small spark will do; if not, the spark
must be greater.
51. Till lately we could only fire warm vapours; but now we can burn hard
dry rosin. And when we can procure greater electrical sparks, we may be
able to fire not only unwarm'd spirits, as lightning does, but even wood,
by giving sufficient agitation to the common fire contained in it, as
friction we know will do.
52. Sulphureous and inflammable vapours arising from the earth, are easily
kindled by lightning. Besides what arise from the earth, such vapours are
sent out by stacks of moist hay, corn, or other vegetables, which heat and
reek. Wood rotting in old trees or buildings does the same. Such are
therefore easily and often fired.
53. Metals are often melted by lightning, tho' perhaps not from heat in the
lightning, nor altogether from agitated fire in the metals.--For as
whatever body can insinuate itself between the particles of metal, and
overcome the attraction by which they cohere (as sundry menstrua can) will
make the solid become a fluid, as well as fire, yet without heating it: so
the electrical fire, or lightning, creating a violent repulsion between the
particles of the metal it passes thro', the metal is fused.
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 nail before a part would
melt, must burn the board it sticks in. And the melted part would burn the
floor it dropp'd on. But if a sword can be melted in the scabbard, and
money in a man's pocket, by lightning, without burning either, it must be a
cold fusion.
55. Lightning rends some bodies. The electrical spark will strike a hole
thro' a quire of strong paper.
56. If the source of lightning, assigned in this paper, be the true one,
there should be little thunder heard at sea far from land. And accordingly
some old sea-captains, of whom enquiry has been made, do affirm, that the
fact agrees perfectly with the hypothesis; for that, in crossing the great
ocean, they seldom meet with thunder till they come into soundings; and
that the islands far from the continent have very little of it. And a
curious observer, who lived 13 years at _Bermudas_, says, there was less
thunder there in that whole time than he has sometimes heard in a month at
_Carolina_.
ADDITIONAL PAPERS.
TO
Mr. PETER COLLINSON, F.R.S. _London_.
PHILADELPHIA, _July 29, 1750_
_SIR_,
As you first put us on electrical experiments, by sending to our library
company a tube, with directions how to use it; and as our honourable
proprietary enabled us to carry those experiments to a greater height, by
his generous present of a compleat electrical apparatus; 'tis fit that both
should know from time to time what progress we make. It was in this view I
wrote and sent you my former papers on this subject, desiring, that as I
had not the honour of a direct correspondence with that bountiful
benefactor to our library, they might be communicated to him through your
hands. In the same view I write, and send you this additional paper. If it
happens to bring you nothing new (which may well be, considering the number
of ingenious men in _Europe_, continually engaged in the same researches)
at least it will show, that the instruments, put into our hands, are not
neglected; and, that if no valuable discoveries are made by us, whatever
the cause may be, it is not want of industry and application.
_I am, Sir,
Your much obliged
Humble Servant_,
B. FRANKLIN.
OPINIONS and CONJECTURES,
_Concerning the Properties and Effects of the electrical Matter, arising
from Experiments and Observations, made in_ Philadelphia, 1749.
§ 1. The electrical matter consists of particles extreamly subtile, since
it can permeate common matter, even the densest metals, with such ease and
freedom, as not to receive any perceptible resistance.
2. If any one should doubt, whether the electrical matter passes thro' the
substance of bodies, or only over and along their surfaces, a shock from an
electrified large glass jar, taken thro' his own body, will probably
convince him.
3. Electrical matter differs from common matter in this, that the parts of
the latter mutually attract, those of the former mutually repel, each
other. Hence the appearing divergency in a stream of electrified effluvia.
4. But tho' the particles of electrical matter do repel each other, they
are strongly attracted by all other matter.[7]
5. From these three things, the extreme subtilty of the electrical matter,
the mutual repulsion of its parts, and the strong attraction between them
and other matter, arise this effect, that when a quantity of electrical
matter, is applied to a mass of common matter, of any bigness or length
within our observation (which has not already got its quantity) it is
immediately and equally diffused through the whole.
6. Thus common matter is a kind of spunge to the electrical fluid. And as a
spunge would receive no water, if the parts of water were not smaller than
the pores of the spunge; and even then but slowly, if there were not a
mutual attraction between those parts and the parts of the spunge; and
would still imbibe it faster, if the mutual attraction among the parts of
the water did not impede, some force being required to separate them; and
fastest, if, instead of attraction, there were a mutual repulsion among
those parts, which would act in conjunction with the attraction of the
spunge. So is the case 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 substance. If more is added, it lies without
upon the surface, and forms what we call an electrical atmosphere: and then
the body is said to be electrified.
8. 'Tis supposed, that all kinds of common matter do not attract and retain
the electrical, with equal strength and force; for reasons to be given
hereafter. And that those called electrics _per se_, as glass, &c. attract
and retain it strongest, and contain the greatest quantity.
9. We know that the electrical fluid is _in_ common matter, because we can
pump it _out_ by the globe or tube. We know that common matter has near as
much as it can contain, because, when we add a little more to any protion
of it, the additional quantity does not enter, but forms an electrical
atmosphere. And we know that common matter has not (generally) more than it
can contain, otherwise all loose portions of it would repel each other, as
they constantly do when they have electric atmospheres.
10. The beneficial uses of this electrical fluid in the creation, we are
not yet well acquainted with, though doubtless such there are, and those
very considerable; but we may see some pernicious consequences, that would
attend 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 dust and other light matters that get loose from it,
would, by virtue of their separate electrical atmospheres, not only repel
each other, but be repelled from the earth, and not easily be brought to
unite with it again; whence our air would continually be more and more
clogged with foreign matter, and grow unfit for respiration. This affords
another occasion of adoring that wisdom which has made all things by weight
and measure!
11. If a piece of common matter be supposed intirely free from electrical
matter, and a single particle of the latter be brought nigh, 'twill be
attracted and enter the body, and take place in the center, or where the
attraction is every way equal. If more particles enter, they take their
places where the balance is equal between the attraction of the common
matter and their own mutual repulsion. 'Tis supposed they form triangles,
whose sides shorten as their number increases; 'till the common matter has
drawn in so many, that its whole power of compressing those triangles by
attraction, is equal to their whole power of expanding themselves by
repulsion; and then will such piece of matter receive no more.
12. When part of this natural proportion of electrical fluid, is taken out
of a piece of common matter, the triangles formed by the remainder, are
supposed to widen by the mutual repulsion of the parts, until they occupy
the whole piece.
13. When the quantity of electrical fluid taken from a piece of common
matter is restored again, it enters, the expanded triangles being again
compressed 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 electrical fluid. Suspend them
by silk lines from the ceiling. Apply the wire of a well-charged vial, held
in your hand, to one of them (A) Fig. 7. and it will receive from the wire
a quantity of the electrical fluid; but will not imbibe it, being already
full. The fluid therefore will flow round its surface, and form an
electrical atmosphere. Bring A into contact with B, and half the electrical
fluid is communicated, so that each has now an electrical atmosphere, and
therefore they repel each other. Take away these atmospheres by touching
the balls, and leave them in their natural state: then, having fixed a
stick of sealing wax to the middle of the vial to hold it by, apply the
wire to A, at the same time the coating touches B. Thus will a quantity of
the electrical fluid be drawn out of B, and thrown on A. So that A will
have a redundance of this fluid, which forms an atmosphere round it, and B
an exactly equal deficiency. Now bring these balls again into contact, and
the electrical atmosphere will not be divided between A and B, into two
smaller atmospheres as before; for B will drink up the whole atmosphere of
A, and both will be found again in their natural state.
15. The form of the electrical atmosphere is that of the body it surrounds.
This shape may be rendered visible in a still air, by raising a smoke from
dry rosin, dropt into a hot tea-spoon under the electrised body, which will
be attracted and spread itself equaly on all sides, covering and concealing
the body. And this form it takes, because it is attracted by all parts of
the surface of the body, tho' it cannot enter the substance already
replete. Without this attraction it would not remain round the body, but
dissipate in the air.
16. The atmosphere of electrical particles surrounding an electrified
sphere, is not more disposed to leave it or more easily drawn off from any
one part of the sphere than from another, because it is equally attracted
by every part. But that is not the case with bodies of any other figure.
From a cube it is more easily drawn at the corners than at the plane sides,
and so from the angles of a body of any other form, and still most easily
from the angle that is most acute. Thus if a body shaped as A, B, C, D, E,
in Fig. 8, be electrified, or have an electrical atmosphere communicated to
it, and we consider every side as a base on which the particles rest and by
which they are attracted, one may see, by imagining a line from A to F, and
another from E to G, that the portion of the atmosphere included in F, A,
E, G, has the line A, E, for its basis. So the portion of atmosphere
included in H, A, B, I, has the line A, B, for its basis. And likewise the
portion included in K, B, C, L, has B, C, to rest on; and so on the other
side of the figure. Now if you would draw off this atmosphere with any
blunt smooth body, and approach the middle of the side A, B, you must come
very near before the force of your attracter exceeds the force or power
with which that side holds its atmosphere. But there is a small portion
between I, B, K, that has less of the surface to rest on, and to be
attracted by, than the neighbouring portions, while at the same time there
is a mutual repulsion between its particles and the particles of those
portions, therefore here you can get it with more ease or at a greater
distance. Between F, A, H, there is a larger portion that has yet a less
surface to rest on and to attract it; here therefore you can get it away
still more easily. But easiest of all between L, C, M, where the quantity
is largest, and the surface to attract and keep it back the least. When you
have drawn away one of these angular portions of the fluid, another
succeeds in its place, from the nature of fluidity and the mutual repulsion
beforementioned; and so the atmosphere continues flowing off at such angle,
like a stream, till no more is remaining. The extremities of the portions
of atmosphere over these angular parts are likewise at a greater distance
from the electrified body, as may be seen by the inspection of the above
figure; the point of the atmosphere of the angle C, being much farther from
C, than any other part of the atmosphere over the lines C, B, or B, A: And
besides the distance arising from the nature of the figure, where the
attraction is less, the particles will naturally expand to a greater
distance by their mutual repulsion. On these accounts we suppose
electrified bodies discharge their atmospheres upon unelectrified bodies
more easily and at a greater distance from their angles and points than
from their smooth sides.--Those points will also discharge into the air,
when the body has too great an electrical atmosphere, without bringing any
non-electric near, to receive what is thrown off: For the air, though an
electric _per se_, yet has always more or less water and other non-electric
matters mixed with it; and these attract and receive what is so discharged.
17. But points have a property, by which they _draw on_ as well as _throw
off_ the electrical fluid, at greater distances than blunt bodies can. That
is, as the pointed part of an electrified body will discharge the
atmosphere of that body, or communicate it farthest to another body, so the
point of an unelectrified body, will draw off the electrical atmosphere
from an electrified body, farther than a blunter part of the same
unelectrified body will do. Thus a pin held by the head, and the point
presented to an electrified body, will draw off its atmosphere at a foot
distance; where if the head were presented instead of the point, no such
effect would follow. To understand this, we may consider, that if a person
standing on the floor would draw off the electrical atmosphere from an
electrified body, an iron crow and a blunt knitting kneedle held
alternately in his hand and presented for that purpose, do not draw with
different forces in proportion to their different masses. For the man, and
what he holds in his hand, be it large or small, are connected with the
common mass of unelectrified matter; and the force with which he draws is
the same in both cases, it consisting in the different proportion of
electricity in the electrified body and that common mass. But the force
with which the electrified body retains its atmosphere by attracting it, is
proportioned to the surface over which the particles are placed; i.e. four
square inches of that surface retain their atmosphere with four times the
force that one square inch retains its atmosphere. And as in plucking the
hairs from the horse's tail, a degree of strength insufficient to pull away
a handful at once, could yet easily strip it hair by hair; so a blunt body
presented cannot draw off a number of particles at once, but a pointed one,
with no greater force, takes them away easily, particle by particle.
18. These explanations of the power and operation of points, when they
first occurr'd to me, and while they first floated in my mind, appeared
perfectly satisfactory; but now I have wrote them, and consider'd them more
closely in black and white, I must own I have some doubts about them: yet
as I have at present nothing better to offer in their stead, I do not cross
them out: for even a bad solution read, and its faults discover'd, has
often given rise 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 laws; 'tis enough if we know the laws themselves. 'Tis of real
use to know, that china left in the air unsupported will fall and break;
but _how_ it comes to fall, and _why_ it breaks, are matters of
speculation. 'Tis a pleasure indeed to know them, but we can preserve our
china without it.
20. Thus in the present case, to know this power of points, may possibly be
of some use to mankind, though we should never be able to explain it. The
following experiments, as well as those in my first paper, show this power.
I have a large prime conductor made of several thin sheets of Fuller's
pasteboard form'd into a tube, near 10 feet long and a foot diameter. It is
cover'd with _Dutch_ emboss'd paper, almost totally gilt. This large
metallic surface supports a much greater electrical atmosphere than a rod
of iron of 50 times the weight would do. It is suspended by silk lines, and
when charg'd will strike at near two inches distance, a pretty hard stroke
so as to make one's knuckle ach. Let a person standing on the floor present
the point of a needle at 12 or more inches distance from it, and while the
needle is so presented, the conductor cannot be charged, the point drawing
off the fire as fast as it is thrown on by the electrical globe. Let it be
charged, and then present the point at the same distance, and it will
suddenly be discharged. In the dark you may see a light on the point, when
the experiment is made. And if the person holding the point stands upon
wax, he will be electrified by receiving the fire at that distance. Attempt
to draw off the electricity with a blunt body, as a bolt of iron round at
the end and smooth (a silversmith's iron punch, inch-thick, is what I use)
and you must bring it within the distance of three inches before you can do
it, and then it is done with a stroke and crack. As the pasteboard tube
hangs loose on silk lines, when you approach it with the punch iron, it
likewise will move towards the punch, being attracted while it is charged;
but if at the same instant a point be presented as before, it retires
again, for the point discharges it. Take a pair of large brass scales, of
two or more feet beam, the cords of the scales being silk. Suspend the beam
by a packthread from the cieling, so that the bottom of the scales may be
about a foot from the floor: The scales will move round in a circle by the
untwisting of the packthread. Set the iron punch on the end upon the floor,
in such a place as that the scales may pass over it in making their circle:
Then electrify one scale by applying the wire of a charged phial to it. As
they move round, you see that scale draw nigher to the floor, and dip more
when it comes over the punch; and if that be placed at a proper distance,
the scale will snap and discharge its fire into it. But if a needle be
stuck on the end of the punch, its point upwards, the scale, instead of
drawing nigh to the punch and snapping, discharges its fire silently
through the point, and rises higher 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' so much higher than the needle, will not attract the scale and
receive its fire, for the needle will get it and convey it away, before it
comes nigh enough for the punch to act. And this is constantly observable
in these experiments, that the greater quantity of electricity on the
pasteboard tube, the farther it strikes or discharges its fire, and the
point likewise will draw it off at a still greater distance.
Now if the fire of electricity and that of lightening be the same, as I
have endeavour'd to show at large in a former paper, this pasteboard tube
and these scales may represent electrified clouds. If a tube of only 10
feet long will strike and discharge its fire on the punch at two or three
inches distance, an electrified cloud of perhaps 10,000 acres, may strike
and discharge on the earth at a proportionably greater distance. The
horizontal motion of the scales over the floor, may represent the motion of
the clouds over the earth; and the erect iron punch, a hill or high
building; and then we see how electrified clouds passing over hills or high
buildings at too great a height to strike, may be attracted lower till
within their striking distance. And lastly, if a needle fix'd on the punch
with its point upright, or even on the floor below the punch, will draw the
fire from the scale silently at a much greater than the striking distance,
and so prevent its descending towards the punch; or if in its course it
would have come nigh enough to strike, yet being first deprived of its fire
it cannot, and the punch is thereby secured from the stroke. I say, if
these things are so, may not the knowledge of this power of points be of
use to mankind, in preserving houses, churches, ships, &c. from the stroke
of lightning, by directing us to fix on the highest parts of those
edifices, upright rods of iron made sharp as a needle, and gilt to prevent
rusting, and from the foot of those rods a wire down the outside of the
building into the ground, or down round one of the shrouds of a ship, and
down her side till it reaches the water? Would not these pointed rods
probably draw the electrical fire silently out of a cloud before it came
nigh enough to strike, and thereby secure us from that most sudden and
terrible mischief?
21. To determine the question, whether the clouds that contain lightning
are electrified or not, I would propose an experiment to be try'd where it
may be done conveniently. On the top of some high tower or steeple, place a
kind of sentry-box, (as in FIG. 9.) big enough to contain a man and an
electrical stand. From the middle of the stand, let an iron rod rise and
pass bending out of the door, and then upright 20 or 30 feet, pointed very
sharp at the end. If the electrical stand be kept clean and dry, a man
standing on it when such clouds are passing low, might be electrified and
afford sparks, the rod drawing fire to him from a cloud. If any danger to
the man should be apprehended (though I think there would be none) let him
stand on the floor of his box, and now and then bring near to the rod, the
loop of a wire that has one end fastened to the leads, he holding it by a
wax handle; so the sparks, if the rod is electrified, will strike from the
rod to the wire, and not affect him.
22. Before I leave this subject of lightning, I may mention some other
similarities between the effects of that, and these of electricity.
Lightning has often been known to strike people blind. A pigeon that we
struck dead to appearance by the electrical shock, recovering life, droop'd
about the yard several days, eat nothing though crumbs were thrown to it,
but declined and died. We did not think of its being deprived of sight; but
afterwards a pullet struck dead in like manner, being recovered by
repeatedly blowing into its lungs, when set down on the floor, ran headlong
against the wall, and on examination appeared perfectly blind. Hence we
concluded that the pigeon also had been absolutely blinded by the shock.
The biggest animal we have yet killed or try'd to kill with the electrical
stroke, was a well-grown pullet.
23. Reading in the ingenious Dr. _Hales_'s account of the thunder storm at
_Stretham_, the effect of the lightning in stripping off all the paint that
had covered a gilt moulding of a pannel of wainscot, without hurting the
rest 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 effect of a strong electrical
flash sent through that gold from a charged sheet of glass. But having no
paint at hand, I pasted a narrow strip of paper over it; and when dry, sent
the flash through the gilding; by which the paper was torn off from end to
end, with such force, that it was broke in several places, and in others
brought away part of the grain of the Turky-leather in which it was bound;
and convinced me, that had it been painted, the paint would have been
stript off in the same manner with that on the wainscot at _Stretham_.
24. Lightning melts metals, and I hinted in my paper on that subject, that
I suspected it to be a cold fusion; I do not mean a fusion by force of
cold, but a fusion without heat. We have also melted gold, silver, and
copper, in small quantities, by the electrical flash. The manner is this:
Take leaf gold, leaf silver, or leaf gilt copper, commonly called leaf
brass or _Dutch_ gold: cut off from the leaf long narrow strips the breadth
of a straw. Place one of these strips between two strips of smooth glass
that are about the width of your finger. If one strip of gold, the length
of the leaf, be not long enough for the glass, add another to the end of
it, so that you may have a little part hanging out loose at each end of the
glass. Bind the pieces of glass together from end to end with strong silk
thread; then place it so as to be part of an electrical circle, (the ends
of gold hanging out being of use to join with the other parts of the
circle) and send the flash through it, from a large electrified jar or
sheet of glass. Then if your strips of glass remain whole, you will see
that the gold is missing in several places, and instead of it a metallic
stain on both the glasses; the stains on the upper and under glass exactly
similar in the minutest stroke, as may be seen by holding them to the
light; the metal appeared to have been not only melted, but even vitrified,
or otherwise so driven into the pores of the glass, as to be protected by
it from the action of the strongest _Aqua Fortis_ and _Ag: Regia_. I send
you enclosed two little pieces of glass with these metallic stains upon
them, which cannot be removed without taking part of the glass with them.
Sometimes the stain spreads a little wider than the breadth of the leaf,
and looks brighter at the edge, as by inspecting closely you may observe in
these. Sometimes the glass breaks to pieces: once the upper glass broke
into a thousand pieces, looking like coarse salt. These pieces I send you,
were stain'd with _Dutch_ gold. True gold makes a darker stain, somewhat
reddish; silver, a greenish stain. We once took two pieces of thick
looking-glass, as broad as a Gunter's scale, and 6 inches long; and placing
leaf gold between them, put them betwixt two smoothly plain'd pieces of
wood, and fix'd them tight in a book-binder's small press; yet though they
were so closely confined, the force of the electrical shock shivered the
glass into many pieces. The gold was melted and stain'd into the glass as
usual. The circumstances of the breaking of the glass differ much in making
the experiment, and sometimes it does not break at all: but this is
constant, that the stains in the upper and under pieces are exact
counterparts of each other. And though I have taken up the pieces of glass
between my fingers immediately after this melting, I never could perceive
the least warmth in them.
25. In one of my former papers, I mention'd, that gilding on a book, though
at first it communicated the shock perfectly well, yet fail'd after a few
experiments, which we could not account for. We have since found, that one
strong shock breaks the continuity of the gold in the filleting, and makes
it look rather like dust of gold, abundance of its parts being broken and
driven off; and it will seldom conduct above one strong shock. Perhaps this
may be the reason; when there is not a perfect continuity in the circle,
the fire must leap over the vacancies; there is a certain distance which it
is able to leap over according to its strength; if a number of small
vacancies, though each be very minute, taken together exceed that distance,
it cannot leap over them, and so the shock is prevented.
26. From the before mentioned law of electricity, that points, as they are
more or less acute, draw on and throw off the electrical fluid with more or
less power, and at greater or less distances, and in larger or smaller
quantities in the same time, we may see how to account for the situation of
the leaf of gold suspended between two plates, the upper one continually
electrified, the under one in a person's hand standing on the floor. When
the upper plate is electrified, the leaf is attracted and raised towards
it, and would fly to that plate were it not for its own points. The corner
that happens to be uppermost when the leaf is rising, being a sharp point,
from the extream thinness of the gold, draws and receives at a distance a
sufficient quantity of the electrical fluid to give itself an electrical
atmosphere, by which its progress to the upper plate is stopt, and it
begins to be repelled from that plate, and would be driven back to the
under plate, but that its lowest corner is likewise a point, and throws off
or discharges the overplus of the leaf's atmosphere, as fast as the upper
corner draws it on. Were these two points perfectly equal in acuteness, the
leaf would take place exactly in the middle space, for its Weight is a
trifle, compared to the power acting on it: But it is generally nearest the
unelectrified plate, because, when the leaf is offered to the electrified
plate at a distance, the sharpest point is commonly first affected and
raised towards it; so that point, from its greater acuteness, receiving the
fluid faster than its opposite can discharge it at equal distances, it
retires from the electrified plate, and draws nearer to the unelectrified
plate, till it comes to a distance where the discharge can be exactly equal
to the receipt, the latter being lessened, and the former encreased; and
there it remains as long as the globe continues to supply fresh electrical
matter. This will appear plain, when the difference of acuteness in the
corners is made very great. Cut a piece of _Dutch_ gold (which is fittest
for these experiments on account of its greater strength) into the form of
FIG. 10 the upper corner a right angle, the two next obtuse angles, and the
lowest a very acute one; and bring this on your plate under the electrified
plate, in such a manner as that the right-angled part may be first raised
(which is done by covering the acute part with the hollow of your hand) and
you will see this leaf take place much nearer to the upper than to the
under plate; because, without being nearer, it cannot receive so fast at
its right-angled point, as it can discharge at its acute one. Turn this
leaf with the acute part uppermost, and then it takes place nearest the
unelectrified plate, because otherwise it receives faster at its acute
point than it can discharge at its right-angled one. Thus the difference of
distance is always proportioned to the difference of acuteness. Take care
in cutting your leaf to leave no little ragged particles on the edges,
which sometimes form points where you would not have them. You may make
this figure so acute below and blunt above, as to need no under plate, it
discharging fast enough into the air. When it is made narrower, as the
figure between the pricked lines, we call it the _Golden Fish_, from its
manner of acting. For if you take it by the tail, and hold it at a foot or
greater horizontal distance from the prime conductor, it will, when let go,
fly to it with a brisk but wavering motion, like that of an eel through the
water; it will then take place under the prime conductor, at perhaps a
quarter or half an inch distance, and keep a continual shaking of its tail
like a fish, so that it seems animated. Turn its tail towards the prime
conductor, and then it flies to your finger, and seems to nibble it. And if
you hold a plate under it at six or eight inches distance, and cease
turning the Globe, when the electrical atmosphere of the conductor grows
small, it will descend to the plate and swim back again several times with
the same fish-like motion, greatly to the entertainment of spectators. By a
little practice in blunting or sharpening the heads or tails of these
figures, you may make them take place as desired, nearer, or farther from
the electrified plate.
27. It is said in section 8, of this paper, that all kinds of common matter
are supposed not to attract the electrical fluid with equal strength; and
that those called electrics _per se_, as glass, &c. attract and retain it
strongest, and contain the greatest quantity. This latter position may seem
a paradox to some, being contrary to the hitherto received opinion; and
therefore I shall now endeavour to explain it.
28. In order to this, let it first be considered, _that we cannot, by any
means we are yet acquainted with, force the electrical fluid thro' glass_.
I know it is commonly thought that it easily pervades glass, and the
experiment of a feather suspended by a thread in a bottle hermetically
sealed, yet moved by bringing a nibbed tube near the outside of the bottle,
is alledged to prove it. But, if the electrical fluid so easily pervades
glass, how does the vial become _charged_ (as we term it) when we hold it
in our hands? Would not the fire thrown in by the wire pass through to our
hands, and so escape into the floor? Would not the bottle in that case be
left just as we found it, uncharged, as we know a metal bottle so attempted
to be charged would be? Indeed, if there be the least crack, the minutest
solution of continuity in the glass, though it remains so tight that
nothing else we know of will pass, yet the extremely subtile electrical
fluid flies through such a crack with the greatest freedom, and such a
bottle we know can never be charged: What then makes the difference between
such a bottle and one that is sound, but this, that the fluid can pass
through the one, and not through the other?[8]
29. It is true there is an experiment that at first sight would be apt to
satisfy a slight observer, that the fire thrown into the bottle by the
wire, does really pass thro' the glass. It is this: place the bottle on a
glass stand, under the prime conductor; suspend a bullet by a chain from
the prime conductor, till it comes within a quarter of an inch right over
the wire of the bottle; place your knuckle on the glass stand, at just the
same distance from the coating of the bottle, as the bullet is from its
wire. Now let the globe be turned, and you see a spark strike from the
bullet to the wire of the bottle, and the same instant you see and feel an
exactly equal spark striking from the coating on your knuckle, and so on
spark for spark. This looks as if the whole received by the bottle was
again discharged from it. And yet the bottle by this means is charged![9]
And therefore the fire that thus leaves the bottle, though the same in
quantity, cannot be the very same fire that entered at the wire; for if it
were, the bottle would remain uncharged.
30. If the fire that so leaves the bottle be not the same that is thrown in
through the wire, it must be fire that subsisted in the bottle, (that is,
in the glass of the bottle) before the operation began.
31. If so, there must be a great quantity in glass, because a great
quantity is thus discharged even from very thin glass.
32. That this electrical fluid or fire is strongly attracted by glass, we
know from the quickness and violence with which it is resumed by the part
that had been deprived of it, when there is an opportunity. And by this,
that we cannot from a mass of glass draw a quantity of electrical fire, or
electrify the whole mass _minus_, as we can a mass of metal. We cannot
lessen or increase 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 mutual repellency of the particles will admit; and what is already in,
refuses, or strongly repels, any additional quantity. Nor have we any way
of moving the electrical fluid in glass, but one; that is, by covering part
of the two surfaces of thin glass with non-electrics, and then throwing an
additional quantity of this fluid on one surface, which spreading in the
non-electric, and being bound by it to that surface, acts by its repelling
force on the particles of the electrical fluid contained in the other
surface, and drives them out of the glass into the non-electric on that
side, from whence they are discharged, and then those added on the charged
side can enter. But when this is done, there is no more in the glass, nor
less than before, just as much having left it on one side as it received on
the other.
[Illustration]
33. I feel a want of terms here, and doubt much whether I shall be able to
make this part intelligible. By the word _surface_, in this case, I do not
mean mere length and breadth without thickness; but when I speak of the
upper or under surface of a piece of glass, the outer or inner surface of
the vial, I mean length, breadth, and half the thickness, and beg the
favour of being so understood. Now, I suppose, that glass in its first
principles, and in the Furnace, has no more of this electrical 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 vacuum: That the component
parts of glass are extremely small and fine, I guess from its never showing
a rough face when it breaks, but always a polish; and from the smallness of
its particles I suppose the pores between them must be exceeding small,
which is the reason that Aqua-fortis, nor any other menstruum we have, can
enter to separate them and dissolve the substance; nor is any fluid we know
of, fine enough to enter, except common fire, and the electrical fluid. Now
the departing fire leaving a vacuum, as aforesaid, between these pores,
which air nor water are fine enough to enter and fill, the electrical fluid
(which is every where ready in what we call the non-electrics, and in the
non-electric Mixtures that are in the air,) is attracted in: yet does not
become fixed with the substance of the glass, but subsists there as water
in a porous stone, retained only by the attraction of the fixed parts,
itself still loose and a fluid. But I suppose farther, that in the cooling
of the glass, its texture becomes closest in the middle, and forms a kind
of partition, in which the pores are so narrow, that the particles of the
electrical fluid, which enter both surfaces at the same time, cannot go
through, or pass and repass from one surface to the other, and so mix
together; yet, though the particles of electrical fluid, imbibed by each
surface, cannot themselves pass through to those of the other, their
repellency can, and by this means they act on one another. The particles of
the electrical fluid have a mutual repellency, but by the power of
attraction in the glass they are condensed or forced nearer to each other.
When the glass has received and, by its attraction, forced closer together
so much of this electrified fluid, as that the power of attracting and
condensing in the one, is equal to the power of expansion in the other, it
can imbibe no more, and that remains its constant whole quantity; but each
surface would receive more, if the repellency of what is in the opposite
surface did not resist its entrance. The quantities of this fluid in each
surface being equal, their repelling action on each other is equal; and
therefore those of one surface cannot drive out those of the other: but, if
a greater quantity is forced into one surface than the glass would
naturally draw in; this increases the repelling power on that side, and
overpowering the attraction on the other, drives out part of the fluid that
had been imbibed by that surface, if there be any non-electric ready to
receive it: such there is in all cases where glass is electrified to give a
shock. The surface that has been thus emptied by having its electrical
fluid driven out, resumes again an equal quantity with violence, as soon as
the glass has an opportunity to discharge that over-quantity more than it
could retain by attraction in its other surface, by the additional
repellency of which the vacuum had been occasioned. For experiments
favouring (if I may not say confirming) this hypothesis, I must, to avoid
repetition, beg leave to refer you back to what is said of the electrical
phial in my former papers.
34. Let us now see how it will account for several other
appearances.--Glass, a body extremely elastic (and perhaps its elasticity
may be owing in some degree to the subsisting of so great a quantity of
this repelling fluid in its pores) must, when rubbed, have its rubbed
surface somewhat stretched, or its solid parts drawn a little farther
asunder, so that the vacancies in which the electrical fluid resides,
become larger, affording room for more of that fluid, which is immediately
attracted into it from the cushion or hand rubbing, they being supply'd
from the common stock. But the instant the parts of the glass so open'd and
fill'd have pass'd the friction, they close again, and force the additional
quantity out upon the surface, where it must rest till that part comes
round to the cushion again, unless some non electric (as the prime
conductor) first presents to receive it.[10] But if the inside of the globe
be lined with a non-electric, the additional repellency of the electrical
fluid, thus collected by friction on the rubb'd part of the globe's outer
surface, drives an equal quantity out of the inner surface into that
non-electric lining, which receiving it, and carrying it away from the
rubb'd part into the common mass, through the axis of the globe and frame
of the machine, the new collected electrical fluid can enter and remain in
the outer surface, 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
cushion again, the outer surface delivers its overplus fire into the
cushion, the opposite inner surface receiving at the same time an equal
quantity from the floor. Every electrician knows that a globe wet within
will afford little or no fire, but the reason has not before been attempted
to be given, that I know of.
34. So if a tube lined with a [11]non-electric, be rubb'd, little or no
fire is obtained from it. What is collected from the hand in the downward
rubbing stroke, entering the pores of the glass, and driving an equal
quantity out of the inner surface into the non-electric lining: and the
hand in passing up to take a second stroke, takes out again what had been
thrown into the outer surface, and then the inner surface receives back
again what it had given to the non-electric lining. Thus the particles of
electrical fluid belonging to the inside surface go in and out of their
pores every stroke given to the tube. Put a wire into the tube, the inward
end in contact with the non-electric lining, so it will represent the
_Leyden_ bottle. Let a second person touch the wire while you rub, and the
fire driven out of the inward surface when you give the stroke, will pass
through him into the common mass, and return through him when the inner
surface resumes its quantity, and therefore this new kind of _Leyden_
bottle cannot so be charged. But thus it may: after every stroke, before
you pass your hand up to make another, let the second person apply his
finger to the wire, take the spark, and then withdraw his finger; and so on
till he has drawn a number of sparks; thus will the inner surface be
exhausted, and the outer surface charged; then wrap a sheet of gilt paper
close round the outer surface, and grasping it in your hand you may receive
a shock by applying the finger of the other hand to the wire: for now the
vacant pores in the inner surface resume their quantity, and the
overcharg'd pores in the outer surface discharge that overplus; the
equilibrium being restored through your body, which could not be restored
through the glass.[12] If the tube be exhausted of air, a non electric
lining in contact with the wire is not necessary; for _in vacuo_, the
electrical fire will fly freely from the inner surface, without a
non-electric conductor: but air resists its motion; for being itself an
electric _per se_, it does not attract it, having already its quantity. So
the air never draws off an electric atmosphere from any body, but in
proportion to the non-electrics mix'd with it: it rather keeps such an
atmosphere confin'd, which from the mutual repulsion of its particles,
tends to dissipation, and would immediately dissipate _in vacuo_.--And thus
the experiment of the feather inclosed in a glass vessel hermetically
sealed, but moving on the approach of the rubbed tube, is explained: When
an additional quantity of the electrical fluid is applied to the side of
the vessel by the atmosphere of the tube, a quantity is repelled and driven
out of the inner surface of that side into the vessel, and there affects
the feather, returning again into its pores, when the tube with its
atmosphere is withdrawn; not that the particles of that atmosphere did
themselves pass through the glass to the feather.----And every other
appearance I have yet seen, in which glass and electricity are concern'd,
are, I think, explain'd with equal ease by the same hypothesis. Yet,
perhaps, it may not be a true one, and I shall be obliged to him that
affords me a better.
35. Thus I take the difference between non electrics and glass, an electric
_per se_, to consist in these two particulars. 1st, That a non-electric
easily suffers a change in the quantity of the electrical fluid it
contains. You may lessen its whole quantity by drawing out a part, which
the whole body will again resume; but of glass you can only lessen the
quantity contain'd in one of its surfaces; and not that, but by supplying
an equal quantity at the same time to the other surface; so that the whole
glass may always have the same quantity in the two surfaces, their two
different quantities being added together. And this can only be done in
glass that is thin; beyond a certain thickness we have yet no power that
can make this change. And, 2dly, that the electrical fire freely removes
from place to place, in and through the substance of a non-electric, but
not so through the substance of glass. If you offer a quantity to one end
of a long rod of metal, it receives it, and when it enters, every particle
that was before in the rod, pushes its neighbour quite to the further end,
where the overplus is discharg'd; and this instantaneously where the rod is
part of the circle in the experiment of the shock. But glass, from the
smallness of its pores, or stronger attraction of what it contains, refuses
to admit so free a motion; a glass rod will not conduct a shock, nor will
the thinnest glass suffer any particle entring one of its surfaces to pass
thro' to the other.
36. Hence we see the impossibility of success, in the experiments propos'd,
to draw out the effluvial virtues of a non-electric, as cinnamon for
instance, and mixing them with the electrical fluid, to convey them with
that into the body, by including it in the globe, and then applying
friction, etc. For though the effluvia of cinnamon, and the electrical
fluid should mix within the globe, they would never come out together
through the pores of the glass, and so go to the prime conductor; for the
electrical fluid itself cannot come through; and the prime conductor is
always supply'd from the cushion, and that from the floor. And besides,
when the globe is filled with cinnamon, or other non-electric, no
electrical fluid can be obtain'd from its outer surface, for the reason
before-mentioned. I have try'd another way, which I thought more likely to
obtain a mixture of the electrical and other effluvia together, if such a
mixture had been possible. I placed a glass plate under my cushion, to cut
off the communication between the cushion and floor; then brought a small
chain from the cushion into a glass of oil of turpentine, and carried
another chain from the oil of turpentine to the floor, taking care that the
chain from the cushion to the glass touch'd no part of the frame of the
machine. Another chain was fix'd to the prime conductor, and held in the
hand of a person to be electrised. The ends of the two chains in the glass
were near an inch distant from each other, the oil of turpentine between.
Now the globe being turn'd, could draw no fire from the floor through the
machine, the communication that way being cut off by the thick glass plate
under the cushion: it must then draw it through the chains whose ends were
dipt in the oil of turpentine. And as the oil of turpentine being an
electric _per se_, 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 substance of that oil, which we could see in large sparks; and so it
had a fair opportunity of seizing some of the finest particles of the oil
in its passage, and carrying them off with it: but no such effect followed,
nor could I perceive the least difference in the smell of the electrical
effluvia thus collected, from what it has when collected otherwise; nor
does it otherwise affect the body of a person electrised. I likewise put
into a phial, instead of water, a strong purgative liquid, and then charged
the phial, and took repeated shocks from it, in which case every particle
of the electrical fluid must, before it went through my body, have first
gone through the liquid when the phial is charging, and returned through it
when discharging, yet no other effect followed than if it had been charged
with water. I have also smelt the electrical fire when drawn through gold,
silver, copper, lead, iron, wood, and the human body, and could perceive no
difference; the odour is always the same where the spark does not burn what
it strikes; and therefore I imagine it does not take that smell from any
quality of the bodies it passes through. And indeed, as that smell so
readily leaves the electrical matter, and adheres to the knuckle receiving
the sparks, and to other things; I suspect that it never was connected with
it, but arises instantaneously from something in the air acted upon by it.
For if it was fine enough to come with the electrical fluid through the
body of one person, why should it stop on the skin of another?
But I shall never have done, if I tell you all my conjectures, thoughts,
and imaginations, on the nature and operations of this electrical fluid,
and relate the variety of little experiments we have try'd. I have already
made this paper too long, for which I must crave pardon, not having now
time to make it shorter. I shall only add, that as it has been observed
here that spirits will fire by the electrical spark in the summer time,
without heating them, when _Fahrenheit_'s thermometer is above 70; so, when
colder, if the operator puts a small flat bottle of spirits in his bosom,
or a close pocket, with the spoon, some little time before he uses them,
the heat of his body will communicate warmth more than sufficient for the
purpose.
ADDITIONAL EXPERIMENT, _proving that the_ Leyden Bottle _has no more
electrical Fire in it when charged, than before; nor less when
discharged: That in discharging, the Fire does not issue from the Wire
and the Coating at the same Time, as some have thought, but that the
Coating always receives what is discharged by the Wire, or an equal
Quantity; the outer Surface being always in a negative State of
Electricity, when the inner Surface is in a positive State_.
Place a thick plate of glass under the rubbing cushion, to cut off the
communication of electrical fire from the floor to the cushion; then, if
there be no fine points or hairy threads sticking out from the cushion, or
from the parts of the machine opposite to the cushion, (of which you must
be careful) you can get but a few sparks from the prime conductor, which
are all the cushion will part with.
Hang a phial then on the prime conductor, and it will not charge, tho' you
hold it by the coating.----But
Form a communication by a chain from the coating to the cushion, and the
phial will charge.
For the globe then draws the electrical fire out of the outside surface of
the phial, and forces it, through the prime conductor and wire of the
phial, into the inside surface.
Thus the bottle is charged with its own fire, no other being to be had
while the glass plate is under the cushion.
Hang two cork balls by flaxen threads to the prime conductor; then touch
the coating of the bottle, and they will be electrified and recede from
each other.
For just as much fire as you give the coating, so much is discharged
through the wire upon the prime conductor, whence the cork balls receive an
electrical atmosphere. But
Take a wire bent in the form of a C, with a stick of wax fixed to the
outside of the curve, to hold it by; and apply one end of this wire to the
coating, and the other at the same time to the prime conductor, the phial
will be discharged; and if the balls are not electrified before the
discharge, neither will they appear to be so after the discharge, for they
will not repel each other.
Now if the fire discharged from the inside surface of the bottle through
its wire, remained on the prime conductor, the balls would be electrified
and recede from each other.
If the phial really exploded at both ends, and discharged fire from both
coating and wire, the balls would be _more_ electrified and recede
_farther_: for none of the fire can escape, the wax handle preventing.
But if the fire, with which the inside surface is surcharged, be so much
precisely as is wanted by the outside surface, it will pass round through
the wire fixed to the wax handle, restore the equilibrium in the glass, and
make no alteration in the state of the prime conductor.
Accordingly we find, that if the prime conductor be electrified, and the
cork balls in a state of repellency before the bottle is charged, they
continue so afterwards. If not, they are not electrified by that discharge.
CORRECTIONS _and_ ADDITIONS
_to the_ PRECEDING PAPERS.
Page 2, Sect. 1. We since find, that the fire in the bottle is not
contained in the non-electric, but _in the glass_. All that is after said
of the _top_ and _bottom_ of the bottle, is true of the _inside_ and
_outside_ surfaces, and should have been so expressed. _See Sect._ 16, p.
16.
Page 6, Line 13. The equilibrium will soon be restored _but silently_, etc.
This must have been a mistake. When the bottle is full charged, the crooked
wire cannot well be brought to touch the top and bottom so quick, but that
there will be a loud spark; unless the points be sharp, without loops.
Ibid. line ult. _Outside_: add, such moisture continuing up to the cork or
wire.
Page 12, line 14. _By candle-light_ etc. From some observations since made,
I am inclined to think, that it is not the light, but the smoke or
non-electric effluvia from the candle, coal, and red-hot iron, that carry
off the electrical fire, being first attracted and then repelled.
Page 13, line 15. _Windmil wheels_, &c. We afterwards discovered, that the
afflux or efflux of the electrical fire, was not the cause of the motions
of those wheels, but various circumstances of attraction and repulsion.
Page 16, line 21. _Let_ A _and_ B _stand on wax_, &c. We soon found that it
was only necessary for one of them to stand on wax.
Page 19. in the title r. _on_.
Page 24, line 12. r. contact, line 24. confined.
Page 25, line 10. for _stand_ r. _hand_.
Page 28, line 2. _The consequence might perhaps be fatal_, &c. We have
found it fatal to small animals, but 'tis not strong enough to kill large
ones. The biggest we have killed is a hen.
Page 31, line 20. _Ringing of chimes_, &c. This is since done.
Page 33, line 22. _Fails after ten or twelve experiments._ This was by a
small bottle. And since found to fail after with a large glass.
Page 40, sect. 50, 51. _Spirits must be heated before we can fire them_,
&c. We have since fired spirits without heating, when the weather is warm.
_FINIS._
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I. Geography Reform'd: Or, A new System of General Geography according to
an accurate Analysis of the Science, augmented with several necessary
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FOOTNOTES.
[1] We suppose every particle of sand, moisture, or smoke, being first
attracted and then repelled, carries off with it a portion of the
electrical fire; but that the same still subsists in those particles,
till they communicate it to something else; and that it is never
really destroyed.--So when water is thrown on common fire, we do not
imagine the element is thereby destroyed or annihilated, but only
dispersed, each particle of water carrying off in vapour its portion
of the fire, which it had attracted and attached to itself.
[2] Our tubes are made here of green glass, 27 or 30 inches long, as big
as can be grasped. Electricity is so much in vogue, that above one
hundred of them have been sold within these four months past.
[3] To charge a bottle commodiously through the coating, place it on a
glass stand; form a communication from the prime conductor to the
coating, and another from the hook to the wall or floor. When it is
charged, remove the latter communication before you take hold of the
bottle, otherwise great part of the fire will escape by it.
[4] The river that washes one side of _Philadelphia_, as the _Delaware_
does the other; both are ornamented with the summer habitations, of
the citizens, and the agreeable mansions of the principal people of
this colony.
[5] An electrified bumper, is a small thin glass tumbler, near filled with
wine, and electrified as the bottle. This when brought to the lips
gives a shock, if the party be close shaved, and does not breathe on
the liquor.
[6] Thunder-gusts are sudden storms of thunder and lightning, which are
frequently of short duration, but sometimes produce mischievous
effects.
[7] See the ingenious essays on electricity in the Transactions, by Mr
Ellicot.
[8] See the first sixteen Sections of my former Paper, called _Farther
Experiments_, &c.
[9] See § 10 of _Farther Experiments_, &c.
[10] In the dark the electrical fluid may be seen on the cushion in two
semi-circles or half-moons, one on the fore part, the other on the
back part of the cushion, just where the globe and cushion separate.
In the fore crescent the fire is passing out of the cushion into the
glass; in the other it is leaving the glass, and returning into the
back part of the cushion. When the prime conductor is apply'd to take
it off the glass, the back crescent disappears.
[11] Gilt paper, with the gilt face next the glass, does well.
[12] See farther experiments, § 15.
