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Interesting Particulars Concerning the Magnet: Faraday

Faraday found that, when a magnet was approached towards a coil or helix of wire, a current of electricity was generated in that wire at the moment of approach, and that another current in the opposite direction was generated in the wire directly the magnet was withdrawn. The way in which he detected this current was by means of a little instrument called a galvanometer. It consists of a magnetised needle hung on a pivot, so that it can move freely, and inclosed within a coil of wire. Directly an electric current is caused to pass through the wire, the needle is deflected in one direction or the other according to the direction of the current. Such an instrument can be easily made by winding a few yards of covered wire across a common compass. The compass must be then placed so that the needle is parallel with the coil. Immediately a current is sent through the wire, the needle is deflected, and takes up a position east and west, instead of north and south, as before. In this experiment is the germ of one form of electric telegraph, in which such right-hand and left-hand deflections of a needle are translated into letters of the alphabet, and so into words and sentences which are daily being flashed from one end of the world to the other.

Faraday's discovery did not long remain without attempts being made to turn it to some practical advantage. The first of these attempts resulted in the magneto-electric machine of Pixii, who endeavoured by means of a machine to produce the results which Faraday had initiated on his lecture table. In this machine a magnet was caused to spin round beneath two coils of wire, and by these means powerful currents were induced in the wires, and torrents of sparks became evident. Clarke improved upon this idea by causing the little coils to turn, instead of rotating the heavy magnet, which remained stationary. It is a modification of this machine which is now commonly used for medical purposes, and inclosed in a mahogany box, with a handle to turn on the outside. If we peep into one of these boxes, we shall there see the magnet lying along one side, and can observe how the handle is connected with a multiplying arrangement which causes the little coils to revolve very rapidly across its poles. Taking the two terminals, one in each hand, and asking some on else to turn the handles, we shall have very speedy evidence that a magnet can produce a strong current, and shall be only too glad to terminate the experiment.

Of late years these machines have been brought to great perfection, and although space will not allow me to describe them in detail, I may mention that the electric light is now commonly produced by these means. The best known and most effective machines for the purpose are those of Siemens, Gramme, and Brush. Professor Edison, of New York, is said to have invented a magneto-electric machine far surpassing in its results any of those just named; but as these reports are very vague in their character, and as up to the time of writing none of his machines have appeared in this country, I am unable to say anything more concerning them.