Part 8
The whole company may be made to partake of the shock, by joining hands, and forming a circle. The experiment may also be varied if they tread upon each other's toes, or lay their hands upon each other's heads. It might happen, by the latter method, that the whole company would be struck to the ground; but it will be productive of no danger, and very little inconvenience; on the contrary, it has happened that they have neither heard nor felt the shock.
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To exhibit the five following amusements in electricity, the room in which they are performed must be darkened.
_The Miraculous Luminaries._
You must previously prepare the following phosphorus: Calcine common oyster-shells, by burning them in the fire for half an hour; then reduce them to powder; of the clearest of which take three parts, and of flowers of sulphur one part; put the mixture into a crucible, about an inch and a half deep. Let it burn in a strong fire for rather better than an hour; and when it is cool, turn it out and break it in pieces; and, taking those pieces into a dark place, scrape off the parts that shine brightest, which, if good, will be a white powder.
Then construct a circular board, of three or four feet diameter, on the centre of which draw in gum-water, or any adhesive liquid, a half-moon, of three or four inches diameter, and a number of stars round it, at different distances, and of various magnitudes. Strew the phosphorus over the figures, to the thickness of about a quarter of an inch, laying one coat over the other. Place this board behind a curtain; and when you draw the curtain up or back, discharge one electrifying jar or phial over each figure, at the distance of about an inch, and they will become illuminated, exhibiting a very striking resemblance of the moon and stars; and will continue to shine for about half an hour, their splendour becoming gradually more faint.
_The Fiery Shower._
On the plate put a number of any kind of seeds, grains of sand, or brass dust. The conductor being strongly electrified, those light particles will be attracted and repelled by the plate suspended from the conductor, with amazing rapidity, so as to exhibit a perfect fiery shower.
Another way is by a sponge that has been soaked in water. When this sponge is first hung to the conductor, the water will drop from it very slowly; but when it is electrified, the drops will fall very fast, and appear like small globes of fire, illuminating the basin into which they fall.
_The Illuminated Vacuum._
Take a tall receiver that is very dry, and fix through the top of it, with cement, a blunt wire; then exhaust the receiver, and present the knob of the wire to the conductor, and every spark will pass through the vacuum in a broad stream of light, visible through the whole length of the receiver, let it be as tall as it will. This generally divides into a variety of beautiful rivulets, which are continually changing their course, uniting and dividing again in the most pleasing manner.
If a jar be discharged through this vacuum, it presents the appearance 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.)