In the auto-biographical memoirs of sir John Barrow, lately published, he says, when describing some of the employments of his youth: “I had fallen in with an account of Benjamin Franklin’s electrical kite, and a kite being a very common object with school-boys, and a string steeped in salt-water with a glass-handle to it not difficult to be had, I speedily flew my kite, and obtained abundance of sparks (like those obtained from an electrical machine). An old woman, curious to see what I was about, was too tempting an opportunity to not to give her a shock, which so frightened her, that she spread abroad in the village that I was no better than I should be, for that I was drawing down fire from heaven. The alarm ran through the village, and my poor mother entreated me to lay aside my kite.”
It was recently announced by a professor of magic, that several hundred candles would be lighted by one pistol shot. Accordingly, the stage appeared in partial darkness, but, through the gloom, ranges of candles might be indistinctly perceived at different heights from the floor; and, in a minute or two, the performer was seen to enter and discharge a pistol, when all the candles were instantly ignited, and the array of magical instruments appeared strongly illuminated, ready to be employed in the subsequent exploits—an effect always followed by enthusiastic acclamations. And yet there is no difficulty in explaining this prodigy. Candles, carefully prepared to ignite readily, might have above them an arrangement of wires, with the point of a wire just over each wick, and the whole being connected with an electrical battery, they could be ignited instantly, at a moment’s notice. The instant of the performer’s entering, might be the signal for the discharge of the battery by others, and the report of the pistol would prevent any sound being heard on the removal of the wires, which the previous darkness had effectually concealed.
Lord Napier says, that when he was in the Mediterranean, some years ago, and during an awful thunderstorm, he was retiring to rest, when he heard suddenly a cry, from those aloft, of “St. Elmo and St. Anne!” which induced him again to go on deck. On observing the appearance of the masts, the maintop-gallant-mast-head was completely enveloped in a blaze of pale phosphoric light; the other mast-heads presented a similar appearance; the flame preserving its intensity for eight or ten minutes, and then gradually becoming fainter. Yet this appearance, which superstition declared to be miraculous, was only electrical; for, while the solar heat is converting into vapour the water and moisture of the earth, electricity is freely disengaged. “The clouds which this power forms are in different electrical conditions, though the electricity of the atmosphere, when serene, is invariably the same. Hence the descent of clouds towards the earth, their mutual approach, the force of atmospherical currents, and the ever-varying agencies of heat and cold convert the aërial envelope of the globe into a complete electrical apparatus; spontaneously exhibiting, in a variety of forms, the play of the conflict of its antagonist powers. At the close of a sultry day, and above level plains, the opposite electricities of the earth and the air effect their re-union in noiseless flashes of lightning, illuminating, as it were, in far-spread sheets, the whole circuit of the horizon, and the entire canopy of the clouds. At other times, the same elements light up the arctic constellations with their restless wildfires—now diffusing their phosphoric flame, and flitting around in fitful gleams, and now shooting up their auroral columns, advancing, retreating, and contending, as if in mimicry of mortal strife.”[I]
That electricity and magnetism are identical, is evident from many experiments. If a sewing-needle be placed in a wire, twisted in that form called a helix, and a shock of electricity be then passed through it, from a Leyden jar, the needle will be magnetized. The form of the wire, and the manner of placing the needle, are shown in the figure.
Again, if M be a piece of soft iron, of a horse-shoe shape, and surrounded with copper-wire covered with a non-conducting substance, it will become powerfully magnetic on connecting the ends of the wire with a galvanic battery. If this be only of a moderate size, and a keeper, I, be attached to M, it will suspend W, representing a very heavy weight.
Mr. Barlow has so arranged a globe, as to identify the dip of the needle with electricity, a current of which appears to be always passing round the earth. At G, in the opposite diagram, is a globe having a wire covered with silk, coiled entirely over it, from one pole, round and round to the other. The ends of this wire dip into two cups, P and N, connected with the poles of a galvanic battery. When the current passes from this, the small and delicately balanced magnets, m, will show polarity, and dip, just the same as in the earth itself.
Mr. Bain’s electric clock is a remarkable contrivance. Nothing can be more satisfactory or complete. Allowing for wear and tear of materials from friction, and the oxidating influence of the atmosphere, the perpetual motion appears to be realized. As long as the electricity of the earth continues, or, in other words, as long as the laws of nature last, so long will Mr. Bain’s clock continue its oscillations, and register the transit of time. The pendulum conducts, and is the treasury of that power, and two simple wheels and their attachments, with the dead escapement, complete the machine. By an ingenious provision, Mr. Bain’s electric clock at the manufactory extinguishes the gas-light which illuminates its dial, at half-past twelve precisely.