A Story of the Telegraph

by John Murray

A person at one end having, therefore, an electrical machine, by which he could maintain the wire in an electrified state and the pith balls at the other extremity, consequently, in a state of divergence, had it, of course, in his power to give an instantaneous indication to the observer at that farther extremity by touching the wire with the hand, which, discharging the electricity, would allow the balls to collapse for an instant; but instead of merely employing the successive movements of the pith balls to denote the various signals, Mr. Ronalds added another apparatus for the purpose.

Two clocks, very accurately adjusted to the same rate of going, carried, instead of the ordinary seconds hands, light discs, on which the various letters of the alphabet, the figures and other required signals were engraved. These discs turned with a regular step-by-step movement behind a screen of metal in which was made a small opening, sufficient to allow one letter at a time being seen. As the discs turned round each letter in succession would be visible through this space, and it is evident that if the clocks started with the same signal visible, the movement of the discs would bring similar signals into view at the same time.

One of these instruments was situated at each end of the communicating wire.

The operator who was about to transmit any communication watched the dial of his clock until the letter he required was visible and at that instant discharged the wire; the momentary collapse of the balls at the distant end would then warn the observer to note the letter visible on his instrument which would form a part of the intelligence to be received, the successive letters or signals constituting any messages were denoted in this manner, as the clock dials continued to turn round.

In order to avoid the constant attention on the part of the observer an arrangement was adopted by which a pistol could be fired by the spark of the further end to summon the attendant to his instrument.

Various signals were also concerted before hand, by the use of which the time necessary for the transmission of any intelligence was lessened.

These experiments of Mr. Ronalds were made with the intervention of several miles of wire carried backward and forward across his grounds.

In 1819 Professor Oersted, of Copenhagen, made his great discovery of the action of the galvanic current upon a magnetic needle; he observed that when a current is passed along a wire placed parallel and near a magnetic needle free to turn on its centre, the needle is deflected to one side or the other according to the direction in which the current is transmitted.

He further noticed that the position of the wire, whether above or below the needle, had an equal influence with the direction of the current in determining the side to which the deflection took place. The power of a single wire in causing this deviation of a needle is but small, but this was remedied by the invention of the multiplier or galvanometer by Prof. Schweigger, in which the needle being surrounded with many successive coils of insulated wire, is acted upon by the joint force of all. Under a somewhat different form this discovery now forms the basis of the needle electric telegraph.

Very shortly after this important discovery had been made, Arago and Ampère, in France, and Seebeck, in Berlin, succeeded in rendering iron magnetic by the passage of a galvanic current through a wire coiled around the iron, and Sturgeon, in England, produced the first electro-magnet. It was found that provided the iron to be magnetized were perfectly soft and pure, the magnetic property remained only during the actual transmission of the electricity, and was lost immediately on the interruption of the electric current.