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By a happy accident in 1790, Galvani, of Bologna, Italy, while experimenting upon a frog, discovered that he could produce alternate motion between its nerves and muscles through the agency of a fluid generated by certain dissimilar metals when brought close together. Though this mysterious fluid came to be known as the galvanic fluid, and though galvanism was made to perpetuate his name, it was not until 1800 that Volta, another Italian, showed to the scientific world that really a new electricity had been found.

FRANKLIN INSTITUTE, PHILADELPHIA.

(From photo furnished by Institute.)

Volta constructed what became known as the galvanic pile, but more largely since as the voltaic pile, which he found would generate electricity strongly and continuously. He used in its construction the dissimilar metals silver and zinc, cut into disks, and piled alternately one upon the other, but separated by pieces of cloth moistened with salt water. This simple generator of electricity was the forerunner of the more powerful batteries of the present day, and which are still popularly known as voltaic cells or batteries.

But the importance of Volta’s discovery did not lay more in the construction of his electrical generator than in the great scientific fact that chemistry now became linked indissolubly with electricity and electrical effects. The two novel and charming sciences, hitherto separate, were henceforth to coöperate in those majestic revelations and magnificent possibilities which so signally distinguish the nineteenth century. By means of greatly improved voltaic cells or batteries, that is, by jars containing acid in which were suspended dissimilar metals, electricity could be produced readily and in somewhat continuous current. By increasing the number of these cells or jars or batteries, and connecting them with conductors, the current could be made stronger and more effective. In contradistinction to the old frictional or static electricity, the new became known as chemical or current electricity.

As was to have been expected, Volta’s invention and discovery excited the whole domain of electrical science to new investigation, and brought in their train a host of wonderful results, growing more and more practical each year, and pointing the way more and more clearly to the commercial value of electricity as a familiar, inexhaustible, and irresistible power. Thus, in 1801, Nicholson showed that an electric current from a voltaic pile would, when passed through salt water, decompose the water and resolve it into its two original gases, oxygen and hydrogen. In 1807, Sir Humphrey Davy, carrying electricity further into the domain of chemistry, showed, by means of the electric current, that various metallic substances embraced in the earth’s crust, and before his time supposed to be elementary, were really dissoluble and easily resolved into their component parts, whether solids, or gases, or both. Two years later, in 1809, he made the equally momentous discovery of something which was to prove a veritable sit lux, “Let there be light,” for the nineteenth century, and illuminate it beyond all others. Though it had been known almost from the date of the first voltaic pile that, when the ends of its two conducting wires were brought close together, a spark was seen to leap in a curved or arc line from one wire to the other, which phenomenon was known as the voltaic arc, it remained for Davy to exhibit this arc in all the beauty of a brilliant light by using two charcoal (carbon) sticks or electrodes, instead of the wires, at the point of close approach. Here was the first principle of the after-evolved arc light to be found by the end of the century in every large city, and to prove such a source of comfort and safety for their millions of inhabitants. This principle was simply that a stream of electricity pouring along a conducting wire will, when interrupted by a substance such as carbon (charcoal), which is a slow conductor, throw off a bright light at the point of interruption. The phenomenon has been very aptly likened to a running stream of water in whose bed a stone has been placed. The stone obstructs the flow of water. The water remonstrates by an angry ripple and excited roar. In Davy’s experiment with the pieces of charcoal, both became intensely hot while the electricity was making its brilliant arc leap from one to the other, and would, of course, soon be consumed. He, therefore, in showing the principle of a permanent luminant, failed to demonstrate its practical possibilities. These last were not to be attained till the nineteenth century was well along, and only after very numerous and very baffling attempts.

Between 1810 and 1830, many important laws governing electrical phenomena were discovered, which tended greatly to render the science more exact, and to give it commercial direction. Oersted, of Denmark, discovered a means of measuring the strength and direction of an electric current. Ampère, of France, discovered the identity of electricity and what had before been called galvanism. Ritchie, of England, made the first machine by which a continuous motion was produced by means of the attractions and repulsions between fixed magnets and electro-magnets. This machine was an early suggestion of the dynamo and motor of the coming years of the century. It meant that electricity was a source of power, as well as of other phenomenal things.

In speaking of the electro-magnet in connection with Ritchie’s machine, it is proper to say that the electro-magnet was probably discovered between 1825 and 1830, but precisely by whom is not known. It differs from the natural magnet, or the permanent steel horseshoe magnet, and consists simply of a round piece of soft iron, called a core, around which are wrapped several coils of fine wire. When an electric current is made to pass through this wrapping of wire, called the helix, the iron core becomes magnetized, and has all the power of a permanent magnet. But as soon as the electric current ceases, the magnetic power of the core is lost. Hence it is called an electro-magnet, or a temporary magnet, to distinguish it from a permanent magnet.

INDUCTION COIL.

While the discovery of the electro-magnet was very important in the respect that it afforded great magnetic power by the use of a limited or economic galvanic force, or, in other words, by the use of smaller and fewer Voltaic batteries, it was not until Faraday began his splendid series of electrical discoveries, in 1831, that a new and exhaustless wellspring of electricity was found to lay at the door of science. Faraday’s prime discovery was that of the induction of electric currents, or, in other words, of manufacturing electricity directly from magnetism. He began his experiments with what became known as an induction coil, which, though then crude in his hands, is the same in principle to-day. It consists of an iron core wrapped with two coils of insulated wire. One coil is of very lengthy, thin wire, and is called the secondary coil. The other is of short, thick wire, and is called the primary. When a magnetic current is passed through the primary coil, with frequent makes and breaks, it induces an alternating current of very high tension in the secondary coil, thus powerfully increasing its effects. In Faraday’s further study of electric induction, he showed that when a conductor carrying a current was brought near to a second conductor it induced or set up a current in this second. So magnets were found to have a similar effect upon one another.

MAGNETIC FIELDS OF FORCE.

The secret of these phenomena was found to lie in the fact that a magnet, or a conductor carrying a current, was the centre of a field of force of very considerable extent. Such a field of force can be familiarly shown by placing a piece of glass or white paper sprinkled with fine iron filings upon the poles of a magnet. The filings will be drawn into concentric circles, whose extent measures the magnet’s field of force. So also the extent of the field of force surrounding a conductor carrying a current may be familiarly shown. In these instances the filings brought within the fields of force are magnetized. So would any other conducting substance be, and would become capable of carrying away as an independent current that which had been induced in it. Here we have the essential principle of the modern dynamo-electric machine, commonly called simply dynamo. Faraday actually constructed a dynamo, which answered very well for his experiments, but failed in commercial results because the only source of energy he could draw upon in his time was that supplied by the rather costly voltaic cells.

During Faraday’s time and subsequently, electricians in Europe and the United States were active in formulating further laws relative to the nature, strength, and control of electrical currents, and each year was one of preparation for the coming leap of electrical science into the vast realm of commercial convenience and profit.