ELECTRICITY.
No branch of science is more capable of affording amusement, combined with instruction, than electricity, and there are few sciences in which the experiments are more easily performed. We would therefore especially recommend it to our young friends.
The term electricity is derived from the Greek word electron, signifying amber, because electrical attraction was first discovered from its being noticed that when amber was rubbed into a certain degree of warmth, it had the power of attracting small bodies to itself.
Electricity therefore primarily treats of the phenomena and effects produced by the friction or rubbing together of certain bodies called electrics. These consist of glass, amber, resinous matters, silks, hair, wool, feathers, various vegetable substances, and atmospheric air, and the electricity so obtained is usually called Frictional Electricity, to distinguish it from that produced by chemical action, and called Voltaic Electricity.
SIMPLE MEANS OF PRODUCING ELECTRICITY.
To show the nature of electrical action, rub a piece of sealing-wax or amber upon the coat-sleeve, and it will attract light bodies, such as straws or small pieces of paper. If a clean glass tube be rubbed several times through a silken or leather cloth, and presented to any small substances, it will immediately attract and then repel them; and if a poker suspended by a dry silk string be presented to its upper end, then the lower end of the poker will exhibit the same phenomena as the tube itself, which shows that the opposite electrical condition may be induced upon other bodies by the mere neighbourhood and approach of another electrified body, and the effect so produced is called induced electricity.
When an electrified conductor is supported by non-conductors, so that the electric fluid cannot pass from the conductor to the earth, it is said to be insulated: thus the human body is a conductor of electricity—but if a person standing on a glass stool (as represented in the [drawing]) be charged with electricity, the electric fluid cannot pass from him to the earth, and he is said to be insulated; and if he be touched by another person standing on the ground, sparks will be exhibited at the point of contact, where also the person touching will feel a pricking sensation.
ATTRACTION AND REPULSION EXHIBITED.
In order to illustrate certain remarkable facts in this science of an amusing character, attention must be directed to the [figure] A B, which is a metal stand; C is a small piece of cork or pith, which is suspended from the hook by a dry silken thread. Having rubbed an electric, as a dry rod of glass, and presented it to C, the ball will be instantaneously attracted to the glass and will adhere to it. After they remain in contact for a few seconds, if the glass be withdrawn without being touched by the fingers, and again presented to the ball, the latter will be repelled instead of attracted, as in the first instance. By being touched with the finger, the ball can be deprived of its electricity, and if after this has been done we present a piece of sealing-wax in the place of the glass formerly employed, the very same phenomena will take place. On the first application the ball will be attracted, and on the second repelled.[8]
[8] For a more complete account of this interesting science we would refer the young reader to “The Boy’s Playbook on Science,” or, if more advanced, to “Noad’s Manual of Electricity.”
Before the young reader can perform any very important experiments with electricity, he must become possessed of an ELECTRICAL MACHINE, which is an instrument contrived for the purpose of rubbing together the surfaces of glass and leather. They generally consist of a cylinder, or plate of glass, and a piece of silk or leather for it to rub against, covered with an amalgam, the method of preparing which we shall hereafter describe.
HOW TO MAKE AN ELECTRICAL MACHINE.
It is very easy to make a glass machine of the cylindrical form, if the maker cannot afford to buy one. First procure a common wine bottle of good dimensions, and thickish glass. Drill a hole through its bottom, with a file moistened with dilute sulphuric acid. A blacksmith, if supplied with the acid, would undertake to do this part of the work. Through this hole and the mouth pass a spindle, as represented in the [cut]. The end of B should be squared to fix a handle on, and the spindle should be fixed firmly in the bottle. The bottle is then to be fixed in a frame in the [following manner]: the end of the spindle C passes through a hole at B; and the other end at C has the handle for turning the machine.
Next make a cushion of wash-leather stuffed with wool, and fastened to the top of a frame of the following [figure]. This frame is to be of such a height that the cushion shall press against the sides of the bottle, and a piece of black silk is sewn on to the top of the cushion, and hangs over the bottle D. The cushion should be smeared with an amalgam, formed by melting together in the bowl of a tobacco-pipe one part of tin with two of zinc; to which, while fluid, should be added six parts of mercury. These should be stirred about till quite cold, and then reduced to a fine powder in a mortar, and mixed with a sufficient quantity of lard to form a thickish paste. When all is done, the machine is complete.
CUSHION.
THE CONDUCTOR.
The electricity being generated by the friction produced between the rubber and the bottle from the motion imparted by the handle, it is necessary to draw it off for use. This is performed by what is called a conductor. This is made by covering a cylinder of turned wood six inches long and two and a half inches in diameter, and nicely rounded at the ends, with tinfoil, which is then mounted on a stand on a glass rod. When used, it is to be placed in the direction of the length. In it some pins are inserted, with the points outside, in a line even with, and about half an inch from, the bottle, and it should be of such a height as to come just below the silk apron. When it is wished to charge a Leyden jar, it is to be placed at the round end of the conductor. By these simple means a great variety of pleasing experiments may be performed; but to show the various phenomena connected with this interesting study, we shall now describe an electrical machine of the newest construction, and perform our experiments with it.
THE PLATE ELECTRICAL MACHINE.
Formerly the electrical machine was made in the form of a cylinder, but now it consists of a plate A, as seen in the [engraving]. The plate is turned by the handle F through the rubber B B, which diffuses the excitement over the glass. The points or balls at each side of the plate carry off a constant stream of positive electricity to the prime conductor C. Negative electricity is generated by insulating the conductor to which the cushion is attached, and continuing the prime conductor with the ground, so as to carry off the fluid collected from the plate.
HOW TO DRAW SPARKS FROM THE TIP OF THE NOSE.
If the person who works the machine be supported on a stool having glass legs, and connected with the conductor by means of a glass rod, the electricity will pass from the conductor to him, and as it cannot get away, owing to the glass on which he stands being a non-conductor, any person on touching him can draw the electricity from him, which will exhibit itself in small sparks as it passes to the person who touches him. If touched on the nose, sparks of fire will issue from it.
HOW TO CHARGE A LEYDEN JAR.
A most useful piece of electrical apparatus is called the Leyden jar, [here] represented. It is employed for the purpose of obtaining a quantity of electricity, which may be applied to any substance. It consists of a glass jar, coated both inside and without, four-fifths of the way up, with tinfoil. A knob rises through a wooden top communicating with the inside of the jar. When it is wished to charge the jar, this knob is applied to the prime conductor of the electrical machine when in action, and a quantity of electricity being given off, the jar will remain charged with it till a connexion is made, by some good conductor of electricity, between the knob and the outside tinfoil. A piece of brass chain must hang from the stem that carries the knob, and connect it with the interior of the jar.
THE ELECTRICAL BATTERY.
If several of these jars be united, a large quantity of electricity can be collected; but, in arranging them, all the interior coatings must be made to communicate by metallic rods, and a similar union must be effected among the exterior coatings. When thus arranged, the whole series may be charged as if they formed but one jar.
For the purpose of making a direct communication between the inner or outer coatings of a jar or battery, by which a discharge is effected, an instrument called a discharging rod is employed. It consists of two bent metallic rods, terminating at one end by brass balls, and connected at another by a joint which is fixed to the end of a glass handle, and which, acting like a pair of compasses, allows of the balls being separated at certain distances. When opened to the proper degree, one of the balls is made to touch the exterior coating, and the other ball is then brought into contact with the knob of the jar, when a discharge is effected; while the glass handle secures the person holding it from the effects of the shock.
DANCING BALLS AND DOLLS.
Get two round pieces of wood, A B, and coat them with tinfoil; or two pieces of metal plate; attach one of them to the prime conductor by a chain, and let it hang about two or three inches from the knob. Place some pith-balls upon the bottom piece of wood B, and bring it under the other. Immediately this is done, and the upper piece is charged with electricity from the machine, the pith-balls will jump up and down, and from one to the other with great rapidity. If some of the pith be formed into little figures, they will also dance and leap about in the most grotesque manner. The same may be made to dance by merely holding the inside of a dry glass tumbler to the prime conductor for a few minutes, while the machine is in action, and then if this be placed over them they will jump about, to the astonishment of the spectators, as the cause of their motions is not quite so apparent.
THE ELECTRICAL KISS.
This amusing experiment is performed by means of the electrical stool. Let any lady challenge a gentleman not acquainted with the experiment to favour her with a salute. The lady thereupon mounts the glass stool, and takes hold of a chain connected with the prime conductor. The machine being then put in motion the gentleman approaches the lady, and immediately he attempts to imprint the seal of soft affection upon her coral lips, a spark will fly in his face, which generally deters him from his rash and wicked intention.
RINGING BELLS.
Bells may be made to ring by electricity in the following manner. Let three small bells be suspended from a brass wire, D D, and supported by a glass pillar A, passing through bell B to the bell E. The electrical apparatus being attached to the knob F, the electricity passes down the wires D D to the bells, which are then positively electrified and attract the clappers C C, that are negatively so, in consequence of being insulated by the silken strings, which are not conductors. The bells therefore attract the clappers till they are charged, when they strike against the centre bell to discharge themselves, and thus a peal is rung on the bells until the electricity is driven off.
WORKING POWER OF ELECTRICITY.
This may be shown in a variety of ways. The subjoined machine will exhibit the principle upon which many ingenious toys may be made by the young philosopher. In the [figure] A is a wooden board or stand, B B B B, four pillars of glass, gutta-percha, or sealing-wax, having fine wires, C C, stretched above. On these rest the rotatory wire or wheel F, having its points turned the reverse ways. By means of a chain attached to the conductor, and to the instrument at B, the electricity passes over the pillar B, up the wire C into the wheel, and off at the points, which causes it to be turned round on an inclined plane till it reaches the top.
THE ELECTRIFIED WIG.
While a person is on the electrical stool, if he be charged with much electricity,
“Each hair will stand on end,
Like quills upon the fretful porcupine.”
A wooden head—not your own, but a real wooden head—with a wig of streaming hair, and a handsome face to correspond, may be made in the following form, with a wire in the neck to support it by, and fixed in the conductor of an electrical machine. When this is put in motion the hair will rise up, as in the [figure], in a manner to astonish even the “big-wigs.”
IMITATION THUNDERCLOUDS.
To show the manner in which thunderclouds perform their operations in the air, A A is a wooden stand, on which are erected two uprights, B B; C C are two small pulleys, over which a silken cord can pull easily; E is another silken line stretched across from one upright to another; on these silken cords two pieces of thin cardboard covered with tinfoil, and cut so as to represent clouds, are to be fixed horizontally, and made to communicate, by means of thin wires F and G, one with the inside, and the other with the outside, of a charged jar, D. Now, by pulling the loop of the silk line, the clouds will be brought near the cloud 2; continue this slowly, until the clouds (which are furnished with two small brass balls) are within an inch of each other, when a beautiful flash, strongly resembling lightning in miniature, will pass from one cloud to the other, restoring electrical equilibrium.
THE LIGHTNING STROKE IMITATED.
If the jar D be put behind the stand, and the cloud 2 removed, a vessel communicating by means of a wire with the outside of the jar may be swum in water under the remaining cloud; the mast being made of two pieces, and but slightly joined together, with a hollow space in one half of the mast, into which the ends of the conductor pass, but do not touch, leaving an interval of about a quarter of an inch between them. The hollow is then filled with gun-cotton, and closed with cork. When the cloud is passed over the vessel, the mast will be struck and shattered to pieces. A strip of tinfoil, arranged with pins over the hollow part of the mast, will show how a continuous conductor will convey the discharge safely away.
THE SPORTSMAN.
[This apparatus] is capable of affording much amusement. A is a stand of wood, B is a common Leyden jar, out of which proceed the wires H H—one terminating in ball F, the other in the ball D—to which are attached a number of pith birds by silken strings; E is a shelf for the birds to rest upon; C is the sportsman; G his gun.
To put this operation in motion the Leyden jar is to be charged with electricity by affixing a chain to the bottom part of it, and connecting it with an electrical machine in the usual manner, or by applying it to a prime conductor, when the birds will fly off the knob to which they are fixed in consequence of their being repelled. If the sportsman and gun be then turned, so that the end of his gun shall touch the knob F, an electric spark will pass from one to the other, a report will be heard, and the birds will fall down as if shot, in consequence of the electricity having been taken from the Leyden jar. There should be a communication between the sportsman and the jar formed of tinfoil, or some metal, as shown by the dotted line on the stand.
Such are a few of many numerous experiments which may be made by the young experimenter, who is fond of science and has any ingenuity; but should he like to amuse himself with an electrifying machine of little cost, he may warm a sheet of brown paper, and then rub it briskly on a teatray with india-rubber; on raising the paper in a dark room, he will see many pretty electrical sparks.
The back of a black tom cat is sometimes recommended as a cheap electrical machine; but as the wishes of the animal have to be consulted, perhaps it is wiser to leave the cat alone.
