Inventions in the Century

by William Henry Doolittle

The discoveries of Ampère as to the laws of electricity have been likened to the discovery of Newton of the law of gravitation.

Still no practical result, that is, no useful machine, had been produced by the electro-magnet.

In 1825 Sturgeon of England bent a piece of wire into the shape of a horse-shoe, insulated it with a coating of sealing wax, wound a fine copper wire around it, thus making a helix, passed a galvanic current through the helix, and thus invented the first practical electro-magnet. But Sturgeon’s magnet was weak, and could not transmit power for more than fifty feet. Already, however, it had been urged that Sturgeon’s magnet could be used for telegraphic purposes, and a futile trial was made. In the field during this decade also labored the German professors Gauss and Weber, and Baron Schilling of Russia. In 1829 Prof. Barlow of England published an article in which he summarised what had been done, and scientifically demonstrated to his own satisfaction that an electro-magnetic telegraph was impracticable, and his conclusion was accepted by the scientific world as a fact. This was, however, not the first nor the last time that scientific men had predicted impracticabilities with electricity which afterwards blossomed into full success. But even before Prof. Barlow was thus arriving at his discouraging conclusion, Prof. Joseph Henry at the Albany Institute in the State of New York had commenced experiments which resulted in the complete and successful demonstration of the power of electro-magnetism for not only telegraph purposes but for almost every advancement that has since been had in this branch of physics. In March 1829 he exhibited at his Institute the magnetic “spool” or “bobbin,” that form of coil composed of tightly-wound, silk-covered wire which he had constructed, and which since has been universally employed for nearly every application of electro-magnetism, of induction, or of magneto-electrics. And in the same year and in 1830 he produced those powerful magnets through which the energy of a galvanic battery was used to lift hundreds of tons of weight.

In view of all the facts now historically established, there can be no doubt that previous to Henry’s experiments the means for developing magnetism in soft iron were imperfectly understood, and that, as found by Prof. Barlow, the electro-magnet which then existed was inapplicable and impracticable for the transmission of power to a distance. Prof. Henry was the first to prove that a galvanic battery of “intensity” must be employed to project the current through a long conductor, and that a magnet of one long wire must be used to receive this current; the first to magnetise a piece of soft iron at a distance and call attention to its applicability to the telegraph; the first to actually sound a bell at a distance by means of the electro-magnet; and the first to show that the principles he developed were applicable and necessary to the practical operation of an effective telegraph system.

Sturgeon, the parent of the electro-magnet, on learning of Henry’s discoveries and inventions, wrote: “Professor Henry has been enabled to produce a magnetic force which totally eclipses every other in the whole annals of magnetism; and no parallel is to be found since the miraculous suspension of the celebrated oriental impostor in his iron coffin.” (Philosophical Magazine and Annals, 1832.)

The third decade was now prepared for the development of the telegraph. As to the telegraph in its broadest sense, as a means for conveying intelligence to a distance quickly and without a messenger, successful experiments of that kind have existed from the earliest times:—from the signal fires of the ancients; from the flag signals between ships at sea, introduced in the seventeenth century by the Duke of York, then Admiral of the English fleet, and afterwards James II of England; from the semaphore telegraph of M. Chappe, adopted by the French government in 1794, consisting of bars pivoted to an upright stationary post, and made to swing vertically or horizontally to indicate certain signals; and from many other forms of earlier and later days.

As to electricity as an agent for the transmission of signals, the idea dates, as already stated, from the discovery of Stephen Gray in 1729, that the electrical influence could be conveyed to a distance by the means of an insulated wire. This was followed by the practical suggestions of Franklin and others. But when, as we have seen, voltaic electricity entered the field, electricity became a more powerful and tractable servant, and distant intelligent signals became one of its first labors.

The second decade was also made notable by the discovery and establishment by George Simon Ohm, a German professor of Physics, of the fundamental mathematical law of electricity: It has been expressed in the following terms: (a) the current strength is equal to the electro-motive force divided by the resistance; (b) the force is equal to the current strength multiplied by the resistance; (c) the resistance is equal to the force divided by the current strength.

The historical development and evolution of the telegraph may be now summarized:—

1. The discovery of galvanic electricity by Galvani—1786-1790.