see, that, in the evolution of telegraphic methods, that feature of the Morse system which was at first thought to be of the highest importance, namely, its capacity for recording the message on paper, has been almost wholly discarded in practice; while the needle telegraph, which in the beginning made no record, now finds almost its only representative in the siphon recorder.

CHAPTER VI.

FARADAY'S DISCOVERY OF INDUCTION AND THE DEVELOPMENT OF THE DYNAMO.

AMONG innumerable contributions to the world's knowledge of electricity, three splendid discoveries stand incomparably above all others. More than all others, these opened new fields for research, and created new possibilities of application. The discovery of the "new electricity" by Galvani, and of a means of generating it by Volta, and Oersted's memorable experiment in which its influence upon the magnet was revealed, have already been described. Magnificent results which have sprung from these two discoveries have been briefly considered, although it cannot justly be affirmed, that, in their development, nothing has been due to the third member of the triad. But the catalogue of the accomplishments of human genius, as worked out along the line of electricity, would be very incomplete if terminated at this point. Nearly all of the more recent and more

striking applications of the electric current, in which almost daily it is being made to serve man in some new capacity, rest upon the last of the three great discoveries, that of electromagnetic induction, by Faraday.

The son of a blacksmith, for a time a newspaper-carrier, a bookbinder's apprentice at the age of thirteen, Michael Faraday, as a youth, enjoyed few facilities for the acquirement of an education. In a common school he learned the rudiments of reading, writing, and arithmetic; but his apprenticeship, which lasted for eight years, afforded some opportunities for satisfying his keen thirst for knowledge. He eagerly devoured scientific literature which fell in his way, and his attention was especially drawn to electricity by the perusal of an article in an encyclopædia which he was employed to bind. A customer of his master's shop, who was a member of the Royal Institution, afforded him the opportunity of attending four lectures on chemistry, given by Sir Humphry Davy in 1812. Of these lectures he made an admirable series of notes. These he neatly transcribed, illustrated, and sent to Davy, with the request that he might be given some employment in the Royal Institution which would enable him to indulge his taste for experiments and study. To this Davy replied, praising the notes, and

promising an interview. At that interview he advised young Faraday to stick to his bookbinding, and "promised to give him the work of the Institution, as well as his own, and that of as many of his friends as he could influence." Shortly after this, however, Davy dismissed his assistant, and, remembering Faraday's desire, he employed him to fill the place. Thus at the age of twenty-two years, and under these not very promising circumstances, he began a career which, for usefulness as well as brilliancy, has perhaps never been eclipsed.

Before entering Davy's laboratory, he had experimented largely in electricity; but, almost of necessity, for several years afterwards, his attention was mostly given to questions of a chemical nature, and indeed, as he declared himself, he was "for nearly twenty years a student," during which time he was laying the foundation for the remarkable series of researches which he afterward carried out.

Reference has already been made to his success in producing continuous rotation of a conducting wire around a magnet, and also the reverse. A little later, about the year 1825, the scientific world was puzzling over an experiment by the famous Arago. It consisted in rotating a copper or brass disk underneath a freely suspended compass-needle: the latter

was deflected, and might, indeed, be made to rotate about the axis of suspension, provided the metallic disk was turned with sufficient rapidity. No one was able to offer a satisfactory explanation of these rotations; but Faraday conceived the idea that they were due to electricity induced in the revolving disk, and so recorded his belief in his note-book. Even earlier than this he was convinced, that, as an electric current affects a magnet, and may even produce magnetism, a magnet, in turn, must be capable of exerting an influence upon an electric current; and from 1825 he occupied himself more or less in the experimental study of the question. He failed to discover anything like an induction effect, and he failed again and again during the next few years. The subject was again taken up in 1831, and on the 29th of August he began that wonderful series of experimental researches in electricity which at once placed him in the front rank of living philosophers, and established his position as the finest experimentalist of the present age.

Faraday's failures arose from the very natural belief that induction in "voltaic" electricity ought to resemble the induction so long known, which occurs when a body charged with electricity is brought near an insulated conductor, in which case a permanent state of electrification