§ 1. There will be the same explosion and shock if the electrified
phial is held in one hand by the hook, and the coating touched with
the other, as when held by the coating, and touched at the hook.
2. To take the charged 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 applied to the globe or tube; as when held by the
coating, and the hook applied[33].
4. But the _direction_ of the electrical fire being different in the
charging, will also be different in the explosion. The bottle charged
through the hook, will be discharged through the hook; the bottle
charged through the coating, will be discharged through the coating,
and not otherways; for the fire must come out the same way it went in.
5. To prove this, take two bottles that were equally charged through
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 through
the hook, the other through the coating: hold that by the coating
which was charged through the hook; and that by the hook which was
charged through 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
electrified, 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 repelled 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[34] 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,
fetching the electric fluid from the one, and delivering it to the
other, till both phials are nearly discharged.
8. When we use the terms of _charging_ and _discharging_ the phial,
it is 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 was 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 formed
between its coating and the floor.
10. But suspend two or more phials on the prime conductor, one
hanging on 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 in proportion 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, it
is done with inconceivable quickness and violence.
12. So a straight spring (though 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 _charged_
with elasticity when bent, and discharged 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 it
is 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
crowded into and condensed in it, as confined by the glass, which
had been our former opinion, we electrified 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 hand, placed a plate of lead on its upper
surface; then electrified 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 dextrously 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 the 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 called an _electrical-battery_,
consisting of eleven panes of large sash-glass, armed 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, _Sec. 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[35]; 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,
p. 72) and, as far as we hitherto know, have carried it farther.
20. The magical picture[36] 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 it is not
the worse. With thin paste, or gum-water, fix the border that is cut
off on the inside 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 hath been cut out, observing to bring
the correspondent 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[37] 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 forty-eight 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 _Sec. 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
through 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 centre, 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. It is 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-cellar. The upper end
of its axis passes through 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 charged 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 makes 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, completes 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,[38] 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 varnished over with turpentine varnish, the
varnish, though dry and hard, is burnt by the spark drawn through
it, and gives a strong smell and visible smoke. And when the spark
is drawn thro' 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. It is 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 furnished 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 broken, much thinner than the upper
half.--If one of these thin bottles be electrified by the coating,
and the spark taken out through 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 were surprised 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 metalline 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 circuit, would not conduct the least
perceptible shock, and indeed when one wire was electrified the other
hardly shewed any signs of its being in connection with it[39]. Even
a thoroughly wet packthread sometimes fails of conducting a shock,
though 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[40].
28. There is one experiment more which surprises 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 electrified 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 electrified _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 been hitherto able to produce nothing
in this way of use to mankind; and the hot weather coming on, when
electrical experiments are not so agreeable, it is proposed to put
an end to them for this season, somewhat humorously, in a party of
pleasure, on the banks of _Skuylkil_[41]. 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[42].
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 _electrified bumpers_[43], under the discharge of guns from the
_electrical battery_.