of a very dense body of fire, darting directly through the centre of
the vacuum, without touching the sides; whereas, when a single spark
passes through, it generally goes more or less to the side, and a
finger placed on the outside of the glass will draw it wherever a
person pleases. If the vessel be grasped by both hands, every spark is
felt like the pulsation of a large artery; and all the fire makes
towards the hands. This pulsation is even felt at some distance from
the receiver, and a light is seen between the hand and the glass.
All this while, the pointed wire is supposed to be electrified
positively; if it be electrified negatively, the appearance is
astonishingly different; instead of streams of fire, nothing is seen
but one uniform luminous appearance, like a white cloud, or the _milky
way_ in a clear star-light night. It seldom reaches the whole length
of the vessel, but generally appears only at the end of the wire, like
a lucid ball.
If a small phial be inserted in the neck of a small receiver, so that
the external surface of the glass be exposed to the vacuum, it will
produce a very beautiful appearance. The phial must be coated on the
inside; and while it is charging, at every spark taken from the
conductor into the inside, a flash of light is seen to dart at the
same time from every part of the external surface of the phial, so as
to quite fill the receiver. Upon making the discharge, the light is
seen to run in a much closer body, the whole coming out at once.
_The Illuminated Cylinder._
Provide a glass cylinder, three feet long, and three inches diameter;
near the bottom of it fix a brass plate, and have another brass plate,
so contrived that you may let it down the cylinder, and bring it as
near the first plate as you desire. Let this cylinder be exhausted and
insulated, and when the upper part is electrified, the electric matter
will pass from one plate to the other, when they are at the greatest
distance from each other that the cylinder will admit. The brass plate
at the bottom of the cylinder will also be as strongly electrified as
if it were connected by a wire to the prime conductor.
The electric matter, as it passes through this vacuum, presents a most
brilliant spectacle, exhibiting sparkling flashes of fire the whole
length of the tube, and of a bright silver hue, representing the most
lively exhalations of the aurora borealis.
_The Electric Aurora Borealis._
Make a Torricellian vacuum[G] in a glass tube, about three feet long,
and hermetically sealed.[H] Let one end of this tube be held in the
hand, and the other applied to the conductor; and immediately the
whole tube will be illuminated from one end; and when taken from the
conductor will continue luminous, without interruption, for a
considerable time, very often about a quarter of an hour. If, after
this, it be drawn through the hand either way, the light will be
uncommonly brilliant, and, without the least interruption, from one
end to the other, even to its whole length. After this operation,
which discharges it in a great measure, it will still flash at
intervals, though it be held only at the extremity, and quite still;
but if it be grasped by the other hand at the same time, in a
different place, strong flashes of light will dart from one end to the
other. This will continue for twenty-four hours, and often longer,
without any fresh excitation. Small and long glass tubes, exhausted of
air, and bent in many irregular crooks and angles, will, when properly
electrified, exhibit a very beautiful representation of vivid flashes
of lightning.
[G] A Torricellian vacuum is made by filling a tube with pure
mercury and then inverting it, in the same manner as in
making a barometer; for as the mercury runs out, all the
space above will be a true vacuum.
[H] A glass is hermetically sealed by holding the end of it
in the flame of a candle, till it begin to melt, and then
twisting it together with a pair of pincers.
_The Electrical Orrery._
By the motion of circulating points, we may in some measure imitate
the revolutions of the heavenly bodies, forming what is called the
_Electrical Orrery_. Let a single wire, with the extremities pointed
and turned, be nicely balanced on a point; fix a small glass ball over
its centre to represent the sun. At one extremity of the wire, let a
small wire be soldered perpendicularly, and on this balance another
small wire with its ends pointed and turned, and having a small pith
ball in its centre, to represent the earth, and a smaller ball of the
same kind at one of the angles, for the moon. Let the whole be
supported upon a glass pillar, and be conducted by a chain proceeding
from the prime conductor to the wire supporting the glass ball. Now,
when the machine is put in motion, the wires will turn round, so that
the ball representing the earth will move round the central ball, and
the little ball at the angle of the smaller wire will at the same time
revolve about the earth.
_The Electrified Cotton._
Take a small lock of cotton, extended in every direction as much as
can conveniently be done, and by a linen thread about five or six
inches long, or by a thread drawn out of the same cotton, tie it to
the end of the prime conductor; then set the machine in motion, and
the lock of cotton, on being electrified, will immediately swell, by
repelling its filaments from one another, and will stretch itself
towards the nearest conductor. In this situation let the cylinder be
kept in motion, and present the end of your finger, or the knob of a
wire, towards the lock of cotton, which will then immediately move
towards the finger, and endeavour to touch it; but take with the
other hand a pointed needle, and present its point towards the cotton,
a little above the end of the finger, and the cotton will be observed
immediately to shrink upwards, and move towards the prime conductor.
Remove the needle, and the cotton will come again towards the finger.
Present the needle, and the cotton will shrink again.
_The Electric Sparks._
When the prime conductor is situated in its proper place, and
electrified by whirling the cylinder, if a metallic wire, with a ball
at its extremity, or the knuckle or a finger be presented to the prime
conductor, a spark will be seen to issue between them, which will be
more vivid, and will be attended with a greater or less explosion,
according as the ball is larger. The strongest and most vivid sparks
are drawn from that end or side of the prime conductor which is
farthest from the cylinder. The sparks have the same appearance
whether they be taken from the positive or negative conductor; they
sometimes appear like a long line of fire reaching from the prime
conductor to the opposed body, and often (particularly when the spark
is long, and different conducting substances in the line of its
direction) it will have the appearance of being bent to sharp angles
in different places, exactly resembling a flash of lightning.
The figure of a spark varies with the superficial dimensions of the
part from which it is taken. If it be drawn from a ball of two or
three inches in diameter, it will have the appearance of a straight
line; but if the ball from which it is drawn be much smaller, as half
an inch in diameter, it will assume the zig-zag appearance above
mentioned.
_Dancing Balls._
Take a common tumbler or glass jar, and having placed a brass ball in
one of the holes of the prime conductor, set the machine in motion,
and let the balls touch the inside of the tumbler; while the ball
touches only one point, no more of the surface of the glass will be
electrified, but by moving the tumblers about, so as to make the ball
touch many points successively, all the points will be electrified, as
will appear by turning down the tumbler over a number of pith or cork
balls placed on a table. These balls will immediately begin to fly
about.
_The Leyden Phial._
When a nail or piece of thick brass wire, &c., is put into a small
apothecary's phial, and electrified, remarkable effects follow; but
the phial must be very dry or warm. Rub it once beforehand with your
finger, on which put some pounded chalk. If a little mercury, or a few
drops of spirit of wine, be put into it, the experiment succeeds the
better. As soon as this phial and nail are removed from the
electrifying glass, or the prime conductor, to which it has been
exposed, is taken away, it throws out a stream of flame so long, that
with this burning-machine in your hand, you may take about sixty steps
in walking about your room. When it is electrified strongly, you may
take it into another room, and there fire spirits of wine with it. If,
while it is electrifying, you put your finger, or a piece of gold
which you hold in your hand, to the nail, you receive a shock which
stuns your arms and shoulders.
A tin tube, or a man placed upon electrics, is electrified much
stronger by these means than in the common way. When you present this
phial and nail it to a tin tube, fifteen feet long, nothing but
experience can make a person believe how strongly it is electrified.
Two thin glasses have been broken by the shock of it. It appears
extraordinary, that when this phial and nail are in contact with their
conducting or non-conducting matter, the strong shock does not follow.
_The Self-moving Wheel._
The self-moving wheel is made of a thin round plate of window-glass,
seventeen inches in diameter, well gilt on both sides, to within two
inches of the circumference. 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, making together 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 and 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.
In a circle on the table which supports the wheel, are fixed twelve
small pillars of glass, at about eleven 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 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 with 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 electrified before by
the other bullet; and thus the wheel increases its motion, till 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 thimble, these bullets moving in the time nearly two thousand
five hundred feet. The thimbles should be 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, complete 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.
_Resin ignited by Electricity._
Wrap some cotton wool, containing as much powdered resin as it will
hold, about one of the knobs of a discharging-rod. Then having charged
a Leyden jar, apply the naked knob of the rod to the external coating,
and the knob enveloped by the cotton to the ball of the wire. The act
of discharging the jar will set fire to the resin.
A piece of phosphorus or camphor wrapped in cotton wool, and used in
the same way, will be much more easily inflamed.
_Spirits ignited by Electricity._
Hang a small ball with a stem to the prime conductor, so that the ball
may project below the conductor. Then warm a little ardent spirit, by
holding it a short time over a candle in a metallic spoon; hold the
spoon about an inch below the ball, and set the machine in motion. A
spark will soon issue from the ball and set fire to the spirits.
This experiment may be varied different ways, and may be rendered very
agreeable to a company of spectators. A person, for instance, standing
upon an electric stool, and communicating with the prime conductor,
may hold the spoon with the spirits in his hand, and another person,
standing upon the floor, may set the spirits on fire, by bringing his
finger within a small distance of it. Instead of his finger he may
fire the spirits with a piece of ice, when the experiment will seem
much more surprising. If the spoon be held by the person standing upon
the floor, and the insulated person bring some conducting substance
over the surface of the spirit, the experiment succeeds as well.
_The Electric Balloon._
Two balloons, made of the allantoides of a calf, are to be filled with
hydrogen gas, of which each contains about two cubic feet. To each of
these is to be suspended, by a silken thread about eight feet long,
such a weight as is just sufficient to prevent it from rising higher
in the air; they are connected, the one with the positive, the other
with the negative conductor, by small wires about 30 feet in length;
and being kept nearly 20 feet asunder, are placed as far from the
machine as the length of the wires will admit. On being electrified,
these balloons will rise up in the air as high as the wire will allow,
attracting each other, and uniting as it were into one cloud, gently
descending.
_The Illuminated Water._
Connect one end of a chain with the outside of a charged phial, and
let the other end lie on the table. Place the end of another piece of
chain at the distance of about a quarter of an inch from the former;
and set a glass decanter of water on these separated ends. On making
the discharge, the water will appear perfectly luminous.
The electric spark may be rendered visible in water, in the following
manner:--Take a glass tube of about half an inch in diameter, and six
inches long; fill it with water, and to each extremity of the tube
adapt a cork, which may confine the water; through each cork insert a
blunt wire, so that the extremities of the wires within the tube may
be very near one another; then, on connecting one of these wires with
the coating of a small charged phial, and touching the other wire with
the knob of it, the shock will pass through the wires, and cause a
vivid spark to appear within their extremities within the tube. The
charge in this experiment must be very weak, or there will be danger
of bursting the tube.
_The Electrified Ball._
Place an ivory ball on the prime conductor of the machine, and take a
strong spark, or send the charge of a Leyden phial through its centre,
and the ball will appear perfectly luminous; but if the charge be not
sent through the centre, it will pass over the surface of the ball and
singe it. A spark made to pass through a ball of box-wood, not only
illuminates the whole, but makes it appear of a beautiful crimson, or
rather a fine scarlet colour.
_Illuminated Phosphorus._
Put some of Canton's phosphorus into a clear glass phial, and stop it
with a glass stopper, or a cork and sealing-wax. If this wire be kept
in a darkened room (which for this experiment must be very dark) it
will give no light; but let two or three strong sparks be drawn from
the prime conductor, when the phial is kept about two inches distant
from the sparks, so that it may be exposed to that light, and this
phial will receive the light and afterwards will appear illuminated
for a considerable time.
This powder may be stuck upon a board by means of the white of an egg,
so as to represent figures of planets, letters, or any thing else, at
the pleasure of the operator, and these figures may be illuminated in
the dark, in the same manner as the above described phial.
A beautiful method of expressing geometrical figures with the above
powder, is to bend small glass tubes, of about the tenth part of an
inch diameter, in the shape of the figure desired, and then to fill
them with the phosphoric powder. These may be illuminated in the
manner described; and they are not so subject to be spoiled, as the
figures represented upon the board frequently are.
_The Luminous Writing._
Small pieces of tin-foil may be stuck on a flat piece of glass, so as
to represent various fanciful figures. Upon the same principle is the
word LIGHT produced, in luminous characters.
It is formed by the small separations of the tin-foil pasted on a
piece of glass fixed in a frame of baked wood. To use this, the frame
must be held in the hand, and the ball presented to the conductor. The
spark will then be exhibited in the intervals composing the word, from
whence it passes to the hook, and thence to the ground by a chain. The
brilliancy of this is equal to that of the spiral tubes.
_The Electric Explosion._
Take a card, a quire of paper, or the cover of a book; and keep it
close to the outside coating of a charged jar: put one knob of the
discharging-rod upon the card, quire of paper, &c., so that, between
the knob and coating of the jar, the thickness of that card or quire
of paper only is interposed; lastly, by bringing the other knob of the
discharged rod near the knob of the jar, make the discharge, and the
electric spark will pierce a hole (or perhaps several) quite through
the card or quire of paper. This hole has a bur raised on each side,
except the card, &c., be pressed hard between the discharging-rod and
the jar. If this experiment be made with two cards instead of one,
which, however, must be kept very little distant from one another,
each of the cards, after the explosion, will be found pierced with one
or more holes, and each hole will have burs on both surfaces of each
card. The hole, or holes, are larger or smaller, according as the
card, &c., is more damp or more dry. It is remarkable, that if the
nostrils are presented to it, they will be affected with a sulphurous,
or rather a phosphoric smell, just like that produced by an excited
electric.
If, instead of paper, a very thin plate of glass, resin, sealing-wax,
or the like, be interposed between the knob of the discharging-rod and
the outside coating of the jar, on making the discharge, this will be
broken in several pieces.
_Electrified Air._
Fix two or three pointed needles into the prime conductor of an
electrical machine, and set the glass in motion so as to keep the
prime conductor electrified for several minutes. If now, an
electometer be brought within the air that is contiguous to the prime
conductor, it will exhibit signs of electricity, and this air will
continue electrified for some time, even after the machine has been
removed into another room. The air, in this case, is electrified
positively; it maybe negatively electrified by fixing the needles in
the negative conductor while insulated, and making a communication
between the prime conductor and the table, by means of a chain or
other conducting substance.
The air of a room may be electrified in another way. Charge a large
jar, and insulate it; then connect two or more sharp-pointed wires or
needles, with the knob of the jar, and connect the outside coating of
the jar with the table. If the jar be charged positively, the air of
the room will soon become positively electrified likewise; but if the
jar be charged negatively, the electricity communicated by it to the
air will also become negative. A charged jar being held in one hand,
and the flame of an insulated candle held in the other being brought
near the knob of the jar, will also produce the same effect.
_Another Electric Orrery._ (See page 92.)
From the prime conductor of an electric machine suspend six concentric
hoops of metal at different distances from each other, in such a
manner as to represent in some measure the proportional distances of
the planets. Under these, and at a distance of about half an inch,
place a metallic plate, and upon this plate, within each of the hoops,
a glass bubble blown very thin and light. On electrifying the hoops,
the bubbles will be immediately attracted by them, and will continue
to move round the hoops as long as the electrification continues. If
the electricity be very strong, the bubbles will frequently be driven
off, run hither and thither on the plate, making a variety of
surprising motions round their axis; after which they will return to
the hoop, and circulate as before; and if the room be darkened, they
will all appear beautifully illuminated with electric light.
_The Electric Ball._
Provide a ball of cork about three-quarters of an inch in diameter,
hollowed out in the internal part by cutting it in two hemispheres,
scooping out the inside, and then joining them together with paste.
Having attached this to a silk thread between three and four feet in
length, suspend it in such a manner that it may just touch the knob of
an electric jar, the outside of which communicates with the ground. On
the first contact it will be repelled to a considerable distance, and
after making several vibrations, will remain stationary; but if a
candle be placed at some distance behind it, so that the ball may be
between it and the bottle, the ball will instantly begin to move, and
will turn round the knob of the jar, moving in a kind of ellipsis as
long as there is any electricity in the bottle. This experiment is
very striking, though the motions are far from being regular; but it
is remarkable that they always affect the elliptical rather than the
circular form.
_To spin Sealing-wax into Threads by Electricity._
Stick a small piece of sealing-wax on the end of a wire, and set fire
to it. Then put an electrical machine in motion, and present the wax
just blown out at the distance of some inches from the prime
conductor. A number of extremely fine filaments will immediately dart
from the sealing-wax to the conductor, on which they will be condensed
into a kind of net-work resembling wool.
If the wire with the sealing-wax be stuck into one of the holes of the
conductor, and a piece of paper be presented at a moderate distance
from the wax, just after it has been ignited, on setting the machine
in motion, a net-work of wax will be formed on the paper. The same
effect, but in a slighter degree, will be produced, if the paper be
briskly rubbed with a piece of elastic gum, and the melting
sealing-wax be held pretty near the paper immediately after rubbing.
If the paper thus painted, as it were, with sealing-wax be gently
warmed by holding the back of it to the fire, the wax will adhere to
it, and the result of the experiment will thus be rendered permanent.
_The Electrified Camphor._
A beautiful experiment of the same nature is made with camphor. A
spoon holding a piece of lighted camphor is made to communicate with
an electrified body, as the prime conductor of a machine; while the
conductor continues electrified by keeping the machine in motion, the
camphor will throw out ramifications, and appear to shoot like a
vegetable.
AMUSEMENTS WITH CARDS.