Great Facts / A Popular History and Description of the Most Remarkable Inventions During the Present Century

by Frederick C. Bakewell

Of the many means by which this object was attempted to be accomplished, it will be only possible, in this general survey, to notice those that mark the first steps of the invention, and the most important of those that have accompanied its progress to the present time.

The first method that suggested itself was to transmit signals by means of pith-ball electrometers. When, for instance, two pith-balls are suspended from a wire that is made to form part of an electric circuit, the electricity communicated to the balls causes them to diverge, and when the electricity in the wire is discharged, they immediately collapse. This action of pith-balls, when electrified, was the simplest mode known of making telegraphic signals, and it was accordingly adopted by several of the early inventors of Electric Telegraphs. The first person who proposed to apply it for that purpose was M. Lesage, of Geneva, in 1774. His plan was to form 24 electric circuits by as many separate wires, insulated from each other in glass tubes; and to place in the circuit, at each communicating station, an equal number of pith-ball electrometers. Each electrometer was to represent a letter of the alphabet, and they were to be brought into action by an excited glass rod. When a communication was to be made, the wires connected with the separate galvanometers were to be charged alternately with electricity by the excited rod of glass; and the person at the receiving station, by noticing which of the electrometers were successively put into action, could spell the words intended to be communicated.

By the means thus proposed, correspondence could have taken place at only short distances, for the charge of an excited glass rod would have been too feeble to produce any sensible effect on the electrometers had the length of the circuit been considerable. This difficulty might have been overcome by substituting the charge of a Leyden jar for the excited glass; but the more serious obstacle to the use of such a telegraph would have been the cost, and the difficulty of insulating the 24 wires required to work it.

Most of the early telegraphic inventors encumbered their inventions with the same obstacle, as they seemed to consider it necessary to have a separate circuit for each letter of the alphabet. It was not so however, with all; for M. Lomond, a Frenchman, who ranks second in the list of telegraphic inventors, modified the principle of M. Lesage, so as to enable him to work with only two wires and one electrometer at each station. With the experience since gained in the application of the needle telegraph, such an arrangement seems very simple, and we are inclined to wonder that it was not generally adopted, especially after M. Lomond had shown the way.

To produce all the requisite signals with a single pith-ball electrometer, it was necessary to vary the durations of each divergence, and to combine several to form a single symbol. Thus, suppose that a single divergence of the pith-balls for a second was understood to signify the letter A; one divergence, followed by an immediate collapse, by discharging the electricity, might signify B; two prolonged divergences might signify C, and two short ones D; and by thus increasing the number and varying the divergences of the two pith-balls, all the letters of the alphabet might be indicated.

A still more direct method of representing the letters of the alphabet was proposed by M. Reizen in 1794, by the application of the means frequently adopted for exhibiting the light of the electric spark. The charge of a Leyden jar was sent through strips of tin foil, pasted on to a flat piece of glass, so as to form several lines, joined at the ends alternately into a continuous circuit. Interruptions were made in the foil by cutting small portions away, at which points brilliant sparks appeared when the jar was discharged. As the interruptions were so contrived as to form letters, and the strips of tin foil were all arranged separately on a long pane of glass, any letter required could be distinctly made visible by discharging the jar through that particular circuit. To produce all the letters of the alphabet in this manner, a separate circuit was required for each.

Another plan, far less feasible, and scarcely deserving of notice, excepting for its peculiarity, was proposed in the following year by M. Cavallo, who suggested the setting fire to combustibles, or the explosion of detonating substances, as the means of signalling intelligence. About the same time several attempts were made by electricians in Spain to transmit signals by electricity, but their plans were not more practicable than those already mentioned, and depended for their effects on the discharge of Leyden jars.

The discovery of voltaic electricity at the beginning of the present century was an important step in the progress of the Electric Telegraph, though several years elapsed before the applicability of the discovery for that purpose became known; and it was not fully appreciated till within the last twenty years.

The electricity generated by the voltaic battery is far greater in quantity than the most powerful electrical machine can excite, whilst its intensity is so feeble that it cannot pass in a spark through the smallest interval of air. It presents, therefore, much less difficulty in the insulation of the wires than frictional electricity, whilst the rapidity of its transmission is for practical purposes equally efficient. The electricity generated by the voltaic battery being great in quantity and feeble in intensity, it is capable also of effecting chemical decomposition and of imparting magnetism, both of which properties have proved eminently useful in perfecting the Electric Telegraph.

The first application of voltaic electricity to telegraphic purposes was made by Mr. Soemmering in 1809. The signals of his telegraph consisted of the bubbles of gas arising from the decomposition of water, during the action of the electric current. His apparatus consisted of a small glass trough, filled with acidulated water, through the bottom part of which were introduced several gold wires corresponding to the letters of the alphabet. The instant that an electric current was sent through any two of the wires, by making connection with a voltaic battery at the transmitting instrument, bubbles of hydrogen gas rose from one of the gold wires, and bubbles of oxygen gas from another; and as the volume of hydrogen gas, liberated during the decomposition of water, exceeds by sixteen times that of the oxygen, it was easy to distinguish them. In this manner all the letters of the alphabet could be indicated by using 24 wires. The object of having gold wires in the decomposing trough was to prevent the oxidation of the metal; for had copper, or any other metal that combines with oxygen, been employed, the points of the wires would soon have become corroded.