Frictional electricity is pre-eminently a winter amusement. Not that it is not equally possible to produce the same result in summer, but then other occupations are forced upon us, while in the long winter evenings, with a good fire to dry the air of the sitting-room, the conditions are particularly favorable to electrical phenomena. If a hard frost sets in the conditions will be still more favorable, as this dries the air and the ground outside, while on a wet evening a large fire and warmer room will be needed to produce as good results.

The following experiments are given as a means of amusement to those who know little or nothing of electrical phenomena. Some of them may be recognized by some readers as being standard experiments, others may possess the charm of novelty. To many, however, the whole series will be new, and it is hoped that these will find a new source of interest opened to them, and that they may possibly be impelled thereby to investigate further concerning the causes of what they see. Frictional electrical machines can be purchased from any electrical instrument makers, at a small price, and with these experiments mentioned are more readily performed. In this article I only mention experiments that can be performed with materials to be found in every house, or the necessaries for which can be procured from a shop for a nominal sum. Friction between two substances of any sort probably always produces electricity; but it can only be made visible under certain circumstances.

For instance, if a stick of sealing-wax is warmed and rubbed with a piece of flannel also warm, they both become electrified. This may be proved by holding the wax near an electrometer, which is simply a bottle through the cork of which a wire is passed which has two pieces of gold leaf fastened to its extremity, when the leaves at once diverge owing to the repelling force of the electricity. The flannel is also electrified, but the electricity soon escapes, through the hand of the operator to the ground.

We now proceed to make a simple experiment on the production of electricity on a larger scale. Take a piece of stout brown paper and hold it in front of a hot fire till all the moisture inherent in it is expelled, and the paper is dry and quite hot. Now take it away suddenly, and holding it against the side of the coat rub it briskly with the sleeve by holding the sleeve in the hand. Take it away and hold it against the wall of the room, to which it will instantly adhere firmly, this adherence being caused by the development of electricity over the surface of the brown paper by the friction it has undergone. The paper can be removed from the wall, and on holding it at a short distance will fly towards it and adhere again. In a short time, however, the electricity departs, and the paper falls to the ground. If the hand is spread open upon the paper as it sticks, the electricity departs at once and the paper falls. A spark can be obtained from the paper, but it is hardly strong enough to be visible. In the next experiment, however, it is plainly to be seen.

Take an ordinary tea-tray and place it on the top of four glass tumblers, which must have previously been made quite hot and dry at the fire. They must also be scrupulously clean, as dirt is a good conductor of electricity. Now take a sheet of foolscap paper, and heat it strongly at the fire until perfectly dry, as the brown paper was. Place it while hot flat on the table and rub it from side to side, from the top to the bottom, with a piece of thick india-rubber. It will now adhere firmly to the table on account of the electricity developed. Take hold of two corners, pull it up, and quickly place it on the tray. On approaching the knuckle of your closed hand to the edge of the tray you will now obtain a brilliant spark, which, if the room is dark, will appear vivid. On removing the paper from the tray, and again approaching the knuckle, another spark will pass, but not so bright as the former. The experiment can be repeated as often as wished by heating and rubbing the paper again.

Now take four more tumblers, heat them as before, and place them on the floor with a board on the top of them. Let someone stand on this board, taking care that he is completely separated from all surrounding objects of furniture, etc., and that his clothes do not touch the table while the experiment is performed. Let him place his hand on the tray while the paper is heated, rubbed, and placed thereon.

He will then become charged with electricity, and if he approaches his hand to any one else’s a spark will pass between them. (This should not be done with susceptible parts of the body, the eyes for example, as it would be rather painful.) Let some one be provided with a spoon in which a little methylated spirit is heated; if the charged person holds his knuckle to this spirit it will instantly be ignited. Small pieces of paper—comic paper figures, etc.—will dance up and down briskly if he holds his hand outspread over them while lying on the table. The same thing will happen if the pieces of paper are placed between the tray and the table when the former is charged by the hot paper, or if the brown paper in the first experiment is held above them when excited.

Now take a needle and place it on the tray, its point projecting over the edge. If the room is now darkened, on placing the excited paper on the tray, the point of the needle will be seen to glow brilliantly for some seconds. This is caused by the electricity escaping into the air from the point of the needle, and is known as the “brush discharge.” The tray will consequently speedily lose its electricity. It will be found to be impossible to get a spark from the tray as long as the needle is on it, as the electricity vastly prefers to escape by the point. The escape of the electricity may be rendered still more evident by means of the following piece of apparatus.

Take two pieces of thin wire about two inches long, and bend each at right angles about an eighth of an inch from each end, both the bent portions being in the same direction. These two pieces of wire are now to be joined together at the middle at right angles by means of a piece of finer wire twisted around them. This finer wire can, with a little care, be caused to form a small cap, in which the point of a needle is inserted, the needle acting as a pivot, so that the bent wires turn freely on top of it (Fig. 1). The needle is supported by thrusting it into a large cork to act as a stand.

A fine wire is then twisted several times around the bottom of the needle, and the whole apparatus is then placed on the tray, the end of the wire attached to the needle being carefully arranged so as to touch the tray, a metallic connection with the tray being essential to success. If the needle can be soldered to a metal stand, or the cork covered with tinfoil, the wire is not needed. On rubbing the paper and placing it on the tray, the electricity passes up the wire into the needle, thence into the wire cross, and escapes by the bent portions of the wires, each of which should be filed to a point. In escaping it electrifies the surrounding air, and this, according to the law that “like electricities repel each other,” has a reacting force on the wire arms. Accordingly the windmill begins to turn, and may attain a tolerable rate of speed if the tray is strongly charged.

Another amusing experiment is that known as the “electrical head of hair.” The head of a wooden doll is taken, and either provided with a real head of hair, which must be combed out straight, or a quantity of cotton is fastened to it to resemble hair.

If the head is fastened to a metal stand, and placed on the tray when the excited paper is laid upon it, the hairs become charged, and consequently repel each other, causing the whole head of hair to stand erect, each hair separate from the rest, thus presenting a most remarkable appearance. For the same reason, if a heap of small pieces of paper, feathers, etc., is laid on the tray, on placing upon it the electrified paper they will jump off in all directions, each being repelled by the others, in the same way as the gold leaves of the electroscope were repelled in the first experiment. If two pieces of pith are suspended by silk threads to a support, so as to hang close to each other, on bringing near them the electrified wax or tray they will be charged and will repel each other for some time. If when charged by the wax a heated glass rod rubbed with silk is brought near to them, they will fly to it, instead of retreating. This seems to indicate a difference between the electricities of the wax and the glass, the former of which has therefore been called negative, and the latter positive.

For giving stronger shocks than the tray is capable of, we may have recourse to the apparatus known as the Leyden jar, which may be easily charged by means of the tray and excited paper. A Leyden jar is thus easily and cheaply constructed: Take an ordinary wide-mouthed pickle bottle and a cork to fit it. Cover the outside with tinfoil, which can be fastened on with gum, and should be laid on as smoothly and as free from creases as possible. Tinfoil can be procured from any chemist. The outside being finished, the inside has to be covered also, which is a work of greater difficulty. It can best be performed by cutting another piece not quite so large as that on the outside of the bottle but of the same shape, and passing into the bottle without creasing it more than can be helped, it can be arranged inside the bottle so as to fit smoothly all round. Now a piece of brass wire is to be passed through the cork, at the end of which is a brass knob, or if simply bent round it will work, though the knob is neater. At the end of the wire which is inside the bottle a brass chain is fastened so as to touch the tinfoil inside the bottle when the cork is inserted. The tinfoil inside and outside the bottle must only reach to the bottom of the neck, leaving a space between it and the cork.

The Leyden jar is now complete, and must be thoroughly warmed before charging it. When quite hot it can be charged by bringing the knob (the jar being held by the outer coating of tinfoil) near the tray, when the excited paper is laid upon it. A spark will pass between the tray and the knob, and this must be repeated several times (say twenty for a first experiment), the jar being charged more fully the more sparks are put into it. Any one now taking the jar in one hand by the outer coating and placing a finger of the other hand near the knob will receive a shock, the severity of which depends on the number of sparks put into the jar. Several people can take the shock by joining hands, the outside one on one side holding the jar, and the outside one on the other side touching the knob. Those in the middle will not feel the shock quite so strongly as those on the outside.

This is an example of the “quick discharge” of a Leyden jar. It can, however, also be discharged slowly, and the following experiment makes use of this faculty. Take three small bells, which can be procured at any toy shop, and remove the clappers. Now suspend two of them by wires at opposite ends of a piece of metal or stout wire about three inches long, and suspend this wire in the center by a bent wire (or wooden, if covered with tinfoil) support, which is fixed to a thick piece of board, covered with tinfoil, to act as a base.

The tinfoil must be in communication with the supporting wire, and the height of the bells must be so adjusted that when the Leyden jar is placed between them with the third bell supported on the knob (the support of the clapper will have to be removed from the bell for this purpose), all three bells will be of equal heights and about half an inch distant from each other. (The diagram Fig. 2 will explain the arrangement.) Now suspend two small brass buttons by silk threads so as to hang between the bells when the Leyden jar is placed in the center. Charge the jar with the tray and replace it in position (of course with the bell on the top); the buttons will then begin to move backwards and forwards between the bells, and the latter will keep up a vigorous chiming until the electricity of the jar is exhausted. In this experiment it is essential that the supports be of metal, or wood covered with tinfoil, as the electricity passes from the inside of the jar to the outside while it is standing upon the tinfoil, by means of the balls, and thus causes them to vibrate.

A candle which has just been blown out, leaving the wick glowing, can easily be lighted by means of the charged Leyden jar if a piece of bent wire is held touching the outer coating and the other end on one side of the wick while the knob is approached to the other, so that the spark passes through the glowing wick. In the same way spirits of wine can be lighted, and gunpowder, guncotton, etc., exploded. To do this, it is best to have two pieces of bent wire provided with handles of glass at the middle. These wires are held by the handles, one in contact with the outer coating, and the other with the inner coating, of the charged Leyden jar. On approaching the other two ends of the wires a spark passes between them, and if a small quantity of gunpowder is placed on a table and the spark is made to pass through it by approaching the wire to either side it will be fired.

There are many other experiments which can be performed by the help of the simple apparatus described, but it would take up too much space to describe them.

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