Electricity may be said to have a finger in most pies. From its manifestations it would appear to be an all-pervading force, and modern research tends always to substantiate this conclusion. Thus two coins—a cent and a quarter—cannot be brought into contact without producing their quotum of electrical force, and in like manner the principles of its working may often be demonstrated by the simplest apparatus.

There are two states which this subtle force assumes, called Static and Dynamic. The former word indicates a condition of rest, and is applied to electricity when stored in suitable magazines ready for discharge at a favorable opportunity, just as water may be held in lofty reservoirs, ready to pour down and perform work—whether useful or otherwise—if the pipes be opened. Dynamic, on the other hand, indicates a state of motion; so that Dynamic Electricity means that it is flowing along conductors from one place, where there is a large quantity of the force, to another less powerful, in the same way as—again using the comparison with water—the latter pours along connecting pipes from a high level to a lower. Phenomena of static electricity are invariably produced by friction, and some experiments of this class will be first described.

The chief element of success in friction electrical experiments is a warm and dry atmosphere. The operations should therefore be conducted in a well-ventilated room where the fire has been burning some time, whilst all apparatus may with advantage have stood warming for some time before.

1. Rub a 6-inch square of brown paper with a warm silk handkerchief, then place flat against the wall or marble fireplace. It should cleave tightly to either of the latter surfaces.

2. Again electrify the brown paper and hold it above any willing person’s head of hair. The locks will fly up towards the paper and appear like bristles. You may then make sure of a safe retreat, and utter side remarks about “wire.”

3. Sprint smartly after the cat, which, like the other apparatus, should have been warming itself on the hearthrug, and having effected a capture, stroke the fur backwards. If the hand be not moist, considerable sparking should occur and be easily visible in a darkened room.

4. By combing dry hair quickly with a warm ebonite comb, and then applying this to the knuckles, distinct sparks may often be obtained.

5. Cut a piece of paper into small confetti, and place near it a stick of sealing-wax or ebonite rod, which has been rubbed with flannel. The paper atoms are attracted to the rod through a distance of one inch or more, and then, contact having once occurred, they immediately drop off.

6. In the previous experiment it was found that the paper atoms having once touched the rod, dropped off directly. This behavior was caused by a sequence of happenings.

First the negatively excited sealing-wax caused positive charges to possess the upper surface of the paper—the equal negative charges being driven downwards—so that, the two kinds of electric energy having a mutual affinity, the paper sprang towards the wax. Immediately they touched, however, the positive charges of the paper were neutralized by the large excess of negative energy from the sealing-wax, and then, since electricities of like sign exercise mutual repulsion, the negative paper was driven from the negative wax.

Now this repulsion of similarly charged particles is demonstrable by a straightforward experiment, whose simplicity of description is in nowise proportionate to its entertainment. In truth, it consists merely of blowing a soap-bubble and catching it upon an excited stick of glass or wax. The bubble becomes electrified, its myriads of particles repel one another, and the beautiful globe expands in size, possibly to breaking point.

7. Scratch any design or word upon a small sheet of indiarubber—such as is used in the manufacture of mats—and then dust over the surface a thoroughly-shaken mixture of red-lead and sulphur. When all excess of the powder has been blown away, the design should appear in grains of red-lead, showing to excellent effect on the gray rubber ground.

8. By the following method a spark of sufficient intensity to light house gas may be obtained from brown paper. Support a salver on four well-dried inverted tumblers, placing a rubber ring between the tray and each glass, and twist a copper wire round a spoon which rests on the tray. The other end of this wire must be held—insulated from the fingers by a piece of indiarubber or by the ordinary covering of the wire—just over the gas-jet, whilst about ¹/₈-inch away is held another piece in metallic connection with the hand; that is, in reality, via the operator’s body with the earth.

Now, if the gas be turned on slightly and a piece of warm brown paper, electrified by stroking vigorously with a dry brush, be placed on the salver, a spark should pass across the ¹/₈-inch gap and ignite the escaping gas. If the spark does not pass at once, approach the wire extremities slightly closer together.

9. The following experiment owes its origin to Gray—an early worker in the field of static electricity: Erect two dry tumblers with a piece of waxed cardboard between, after the fashion shown in Fig. 1, and lay a lath on the top glass. Beneath one end of the lath spread small pieces of paper, over an ebonite or wood surface supported on another inverted glass. Then if a stick of sealing-wax, which has been vigorously rubbed with flannel, be approached to the other end of the lath, the particles of paper will fly backwards and forwards between the lath and the ebonite surface—on which they would normally rest.

10. A simple trick, but one nevertheless causing considerable amusement to spectators, may be arranged in the following manner: Bore a hole carefully at the middle of a wooden meat skewer (A, Fig. 2), of such size as to take a bone knitting-needle tightly (B, Fig. 2).

Sharpen the blunt end of the skewer and mount it so as to turn easily between bearings erected on inverted wine-glasses. These may consist of two wood blocks (C, Fig. 2), in each of which a shallow conical hole is made to receive the points of the skewer. On these stand weights (E, Fig. 2) to keep wood-bearings firm. When this is in position and swings easily, adjust the needle until it balances exactly. It should be at right angles to the skewer, and may be fixed in position, if necessary, with glue or sealing-wax.

Now cut two discs of white paper (D, Fig. 2) of a diameter about 1 inch less than the knitting-needle’s length, and, having printed across one the word “DONE” in large type, glue them—centers at the point where the needle and skewer intersect—on either side of this cross. Erect the apparatus as shown, so that the needle stands vertical, with the blank paper disc facing the audience, and then invite the latter to see if they can effect a movement without either touching or blowing the disc or creating any disturbance whatever. The conditions should preclude any person, except the canny operator, from attaining success. He, however, innocently takes a postcard (previously warmed and dried), tears it sharply in half, and presents one ragged edge to the projecting bone needle. The cardboard became electrified by tearing, and should exercise quite enough attraction on the needle to upset its nice balance, whereupon the other disc becomes visible, together with its notice “DONE.” The audience may take the ambiguous meaning according to their pleasure.

Few further experiments can be performed without the use of special apparatus. So far, we have dealt only with the most minute quantities of electricity, and if more striking effects are to be produced, our stores of energy must be increased.

Fortunately instruments of a fairly wide application may be rudely constructed at home, although, naturally, results must not be looked for comparable to those obtained with perfected apparatus. However, brief directions now follow for the manufacture of such simple instruments, and so, as commencement, let us appropriate two 3-lb. jam pots from which Leyden jars are to be evolved.

Leyden Jars

Procure as much metal foil as possible, either by raiding the nursery or by purchasing some tinfoil-wrapped butter scotch at the confectioner’s, and gum it round the jam jars so as to extend about half-way up the outside (A, Fig. 3).

Next solder stiff brass wires (8 inches long) to two round pieces of metal, so cut as to pass the jar mouths readily. To the other end of one brass rod solder another disc of metal, tin—or, better, brass—nicely smoothed along its two edges by sandpaper. The other brass rod may be looped at its end and have tinfoil wrapped round until a respectable knob be formed, or else have a brass bedstead globe soldered on.

These brass standards are then stood inside, with their metal bases resting on the bottom of the jars and surrounded by lead shot to the same height as that of the tinfoil, without. The finished article should appear something like the sketch shown as Fig. 3.

Gold Leaf Electroscope

Obtain a square glass pickle or preserve jar, to the mouth of which has been fitted a large cork bung (A, Fig. 4). Next take a 7-inch length of ¹/₈-inch brass wire (B, Fig. 4) (similar to that used for the Leyden jars above), and flatten one end by hammering (F, Fig. 5), after having bent it triangular-shape, as in (C, Fig. 4).

A 2¹/₂ inch length of cycle valve-tubing (A, Fig. 5) is to be slipped over the brass rod B (Fig. 5), and then strips of gummed brown paper, 2 inches wide, lapped round and round the rubber-tubing until a paper cylinder some ¹/₄-inch across the outside is formed (C, Fig. 5). Anyway, this paper cylinder must be a good fit for a hole bored through the center of cork (D, Fig. 5), into which, moreover, it must be glued when dry. The stopper, paper, &c., must then be allowed to soak in hot candle wax for an hour or so, wiped clean and put aside to cool. Excess of grease must be particularly removed—with paraffin if necessary—from the plain end of the metal rod, to which we must next solder a brass knob (D, Fig. 4) or, as an alternative, tinfoil may be twisted round a loop in the wire until a ball is formed, as in the case of the Leyden jar.

The next operation is to cut two strips of Dutch metal—or, better, gold leaf—size ³/₄-inch by 2 inches, and gum them on either side of the flattened brass rod triangle (E, Figs. 4 and 5). This is best managed by laying the brass, after being lightly gummed, upon the Dutch metal strips in the correct position, and when fixed trimming off the corners of the leaves close to the sides of the triangle—not, of course, at the base, or no strips will remain to hang down. Dutch metal and beaten gold are both employed in gilding, and should be obtainable in small quantities at any picture-framer’s shop.

If the cork be now fixed in the mouth of the jar and the brass rod adjusted so that the gold leaves hang free of the interior, our electroscope is practically complete. However, a few pieces of calcium chloride, or pumice stone soaked in strong sulphuric acid, may be included at the bottom of the jar (F, Fig. 4), in order to absorb moisture; and lastly, as a brass ball is not always the most satisfactory terminal for this instrument, one other small accessory may be made. This consists of a 2-inch circle of tin, or, preferably, brass (G, Fig. 4), exactly like that fitted to one of the Leyden jars, and to the under side of which is soldered a ring of springy brass (H, Fig. 4) about ³/₄-inch deep, so made as to fit securely on the brass ball terminal. Thus the metal table is adaptable to the brass knob, whenever such an arrangement is required.

Electrophorus

Our Leyden jars have been constructed to store electrical energy, and the gold leaf electroscope to indicate its presence. But we do not yet possess the means of producing this energy in any considerable quantity.

To make an instrument for this purpose proceed as follows: Clean the inner surface of a circular tin lid—diameter 6 inches or 7 inches, and about ⁵/₈-inch deep—(A, Fig. 6), and in the center stand upright on its head a brass screw, whose point has been filed down until it nearly reaches to the level of the upper edge of the lid (B, Fig. 6). Then carefully pour in melted lead or zinc to a depth of ¹/₈-inch. This process is not absolutely necessary, but is advisable if the metal be available and the extra trouble is not distasteful.

When this metal has thoroughly cooled, melt up sufficient rough resin to just overflow the tin, pour it in and allow to solidify properly without the least disturbance (D, Fig. 6).

For the upper part of the electrophorus, take a disc of tin or brass, absolutely flat, and of the same diameter as the resin surface (E, Fig. 6). In the center of its upper side solder a short piece of brass tube (F, Fig. 6), the correct internal width to fit tightly on a 12-inch length of polished wood rod, cut, say, from a walking-stick (G, Fig. 6).

The drawing shows the general arrangement of this electrophorus, wherewith, by the help of a piece of fur, electricity may be generated. A small cavity must be made in the resin, just above the screw (H, Fig. 6), so that the point of the latter may be clearly seen.

Discharger

One last piece of apparatus—the simplest in construction—remains to be made. Bend a piece of stout brass wire into a semicircle (A, Fig. 7); then, having flattened it at the middle, pass through a hole at the end of a wooden handle (B, Fig. 7), and fix in position by means of a tiny glued wedge (C, Fig. 7). Next twist the rod at both ends into loops, and wrap tinfoil round so as to form metal knobs (D, Fig. 7). Brass balls may be used instead. This arrangement is now complete, and we may commence experimenting.

11. Twist a stout piece of copper wire surmounted by a brass or tinfoil ball round the outside coating of a Leyden jar (A, Fig. 8), so that the two knobs are about 3 inches apart. Suspend a pith ball (B, Fig. 8), made from dried wood pith, by silk thread (C, Fig. 8) from some support above, so that it hangs normally midway between the two knobs.

Next excite the resin surface of the electrophorus by rubbing with a dry rabbit’s fur, muff, or flannel; and, holding the cover of this instrument by the handle’s extreme end, place it upon the resin. Remove immediately and bring near to the knob, which connects with the interior of the Leyden condenser, at the same time touching its outer tinfoil surface with the finger. A spark should pass between the electrophorus cover and the Leyden jar, whereupon, if the former and finger be removed, and the pith ball allowed to drop into position, this will oscillate violently to and fro between the knobs.

12. Construct a Leyden jar with knob terminal similar to that previously described, but cover part way up the outside with gold paint (A, Fig. 9), instead of tinfoil. Charge this condenser by means of the electrophorus cover, as described in experiment 11, and if sufficient induction does not take place with one contact, replace the metal disc on the resin and pass a spark to the Leyden condenser knob several times, taking care to touch the gold paint coating with the finger on each occasion. If now the semicircular discharger, held by the wood handle, be brought so that one knob touches that of the Leyden condenser whilst the other moves over the gold-paint surface, long series of sparks, differing greatly in appearance from any previously produced, will pass between the gilt and the discharger.

13. Excite a stick of sealing-wax by rubbing with flannel, and bring it against a pith ball suspended by silk. The sealing-wax was negatively charged, and the pith ball is now in a like condition. To prove this, approach the flannel which excited the wax, and had consequently acquired a positive charge; inasmuch as the pith ball is immediately attracted and we know that positively excited bodies have an affinity for those negatively affected, the pith ball must be of the latter character.

If, further, a glass rod be excited by rubbing with silk and brought near to the negative pith ball, the latter will again be attracted, showing the glass to be positively charged.

On the other hand, the silk rubber repels a pith ball which has been in contact with excited sealing-wax, in the same way as it will repel the latter substance itself if suspended freely, thus indicating that the silk is similarly, i.e. negatively charged.

The phenomenon of positive and negative electricity may be somewhat differently demonstrated by means of the electroscope. Touch the terminal of this instrument with rubbed sealing-wax. The gold leaves diverge. Moreover, they may be thrown farther asunder by bringing the electrophorus resin near, so that evidently the charge of this instrument is also negative. Perhaps as a diversion it may be noted that resin is one of the chief ingredients of sealing-wax. The electroscope leaves remain apart even when the electrified body has been removed, but they may be made to collapse by touching the knob with the finger or bringing an excited glass rod near. The former action “earths” (i.e. connects, via the person’s body, with the house walls and the earth) the gold leaves and allows the electrical charge to escape, whilst the latter operation counteracts the negative charge by virtue of the positively excited glass.

14. If the electrophorus and electroscope be placed as shown in Fig. 10, the gold leaves being already held asunder by a negative charge from sealing-wax, and the cover of the first instrument be lifted, whilst a strip of cardboard bridges from its upper surface to the disc terminal of the electroscope (A, Fig. 10), the instrument’s leaves will fall together again. From this behavior it may be gathered that the charge on the upper surface of the electrophorus cover is positive, or opposite in character to that induced by rubbing on the resin cake.

15. Stand a charged Leyden jar and the electroscope close together on the table. They must not be so near, however, that the gold leaves are affected by the condenser’s presence.

If, now, a few pieces of sulphur, spread upon the Leyden jar’s disc terminal, be ignited so as to burn freely, the gold leaves will immediately diverge slightly, indicating that part of the electric charge, which is being rapidly dissipated by way of the flame into the atmosphere, has traced a path to the electroscope.

16. An amusing variation of experiment 11, wherein a pith ball was rendered restless between the two terminals of a Leyden condenser, is constituted by carefully modeling a little seated figure out of pith and sealing-wax. The mannikin is threaded on a silk strand, so that the legs hang down as though seated on a swing, and is then suspended by tying the two silk ends to a support above. Fig. 11 indicates the arrangements.

Two Leyden jars are next required, of opposite influences. To effect this, charge one by the ordinary method of touching its terminal several times with an electrophorus cover, being careful on each occasion to “earth” the outer surface, whilst the other condenser is charged by presenting its outer surface to the electrophorus cover, and each time touching the knob terminal with the finger, i.e. “earthing” it.

By this method, whilst the charge at the knob of one Leyden jar is positive, that at the terminal of the other is negative. Place these two instruments at equal distances on either side of the “swing” support, and at such an elevation that the pith figure may just touch the brass knobs.

Then, if the swing be started going, it should continue to oscillate for a considerable time. As the pith figure approaches, say, the positive knob, it acquires a negative charge and is thereby attracted. Directly it touches, however, this negative state is counteracted, a positive charge supersedes it, and repulsion between pith figure and positive knob ensues. The pith doll then swings over towards the negative knob and—being positively influenced—is of course attracted until contact takes place. Then negative supersedes positive in the pith figure, repulsion again results, and a similar cycle of changes is repeated. Thus the figure continues to oscillate until the charges of the jars have been exhausted or have leaked away.

17. In the same manner as the alternate attraction and repulsion of a light body has been used to maintain oscillation, so similarly an electrostatic motor may be constructed embodying the same principles. Cut out a 16-pointed star of cardboard, 8-inch diameter, and, having glued a ¹/₄-inch slice of cork in the middle of each side (A, Fig. 12), pass a knitting-needle through the star’s center at right angles (B, Fig. 12). Both ends of this spindle rest in conical cavities (C, Fig. 12), which may be punched or drilled in small brass discs to act as bearings, and the apparatus is mounted as shown.

It is important that the cardboard should be perfectly dry, and with this end in view it may well have previously received a saturation in paraffin wax. When set hard, stick a brass pin bent at right angles into each point of the star, and set Leyden jars of different charges beneath any two diametrically opposite points. The motor, being given a start, should continue to revolve for some time owing to the succeeding attraction and repulsion of the metal pins.

The following description is of a small machine which may be fairly easily constructed, and when in good working order will give far better results than the electrophorus. Fig. 13 shows the reference letters and general arrangement. Two cork bungs (A, Fig. 13), previously saturated with paraffin wax or shellac varnish, are fixed into the ends of a cylindrical lamp chimney, and through a hole in the exact center of each passes a wooden rod (B, Fig. 13), which must be glued in place. Each end is supported in a wooden bearing (C, Fig. 13), black lead being used as a lubricant, and to the protruding one a small handle (D, Fig. 13) is fitted, wherewith the glass may be revolved. Next a long pad of wash leather (E, Fig. 13), stuffed with horse-hair, is fixed so as to press gently against the cylinder, whilst a silk flap (F, Fig. 13) about 2 inches wide hangs over the top surface of the glass. A brass chain (G, Fig. 13) is also fixed to the wash-leather cushion and, in the ordinary way, connects to “earth” either direct or through the operator. The wash-leather cushion is well black-leaded where it touches the glass.

On the opposite side of the cylinder a metal comb (H, Fig. 13) is supported, the teeth being ¹/₁₆-inch away from the glass, whilst the back of the comb is soldered to a brass knob (I, Fig. 13) fixed on a wood pedestal. Any noticeable edges at the base of the brass globe should be filed off until only round surfaces are presented.

Care should be taken to dry the machine thoroughly, and if then the handle be turned regularly, as indicated by the arrow, the brass knob should rapidly become charged to such an extent that sparks may be drawn with the knuckles, possibly with discomforting results!

If the brass ball possess any sharp edges or, alternatively, if a length of wire girdle it so that one end projects radially about one inch, then the electricity will leak from these extremities in the form of a glow discharge as fast as it is developed. This frequently creates such a disturbance in the surrounding air as to distinctly blow a candle flame when held at the discharging point.

In 1752 Faraday invented an arrangement of attraction and repulsion by which three bells were kept ringing. To the electrical machine conductor was attached a metal support from the ends of which hung two bell domes on brass chains, whilst from the center another was supported by a silk strand and connected by a brass chain to earth. Between the bells small brass clappers were hung by silk threads, as shown in Fig. 14.

The action in working was for the machine to charge its conductor and hence the two outer bell domes, which then attracted their brass clappers until contact took place. This caused repulsion, so that the clappers swung over to the center dome, where discharge to earth ensued and a condition obtained when the cycle of events might be repeated.

Having thus arrived, via the simplest phenomena, at a piece of mechanism which will work, our experiments in the field of static electricity must conclude; but rather, let it be noted, on account of a dearth of apparatus than from any scarcity of phenomena to be studied. If therefore the reader foresees an opportunity of pursuing the subject further, such for example as the use of a well-equipped laboratory, let him not hesitate to snatch the advantage. To mention two facts demonstrable by further experiment: (1) Frictional electricity is produced in excessively small quantities at a very high pressure. For this reason sparks in air may be produced frictionally of such a length as cannot be obtained direct from batteries. (2) Friction itself is not a necessary element in the production of electrical energy, but is adopted in order to bring every portion of the rubbed surfaces into perfect contact. Thus far and no further. We must say “Au revoir,” and splash down a full stop.