[THE ELECTRIC TELEGRAPH.]
No application of science has so completely realized the visions of fancy as the Electric Telegraph. So closely, indeed, does the real of the present day approach to the ideal of ages past, that it might be supposed the narratives in the tales of faëry land were true records of the inventions of former times, and that the combined efforts of inventive genius during the last half century were but imitations and reproductions of what had been successfully accomplished "once upon a time." There is also an intermediate period—between the indefinite of faëry tales and the positive of scientific history—in which sympathetic tablets and magical loadstones, scarcely less mythical, are stated to have been invented; and the individuals are named who thus paved the way for instantaneous communication between all parts of the world.
The Jesuits of the sixteenth and seventeenth centuries took the place of the magicians of the Middle Ages. In the seclusion of their monasteries, they speculated on the mysterious powers of Nature, then partially revealed to them, and shadowed forth images of their possible applications. It is to a vague speculation of this kind that we may attribute the notice given by Strada, in his "Prolusiones Academicæ," of the sympathetic magnetic needles, by which two friends at a distance were able to communicate; though the then fanciful idea has been literally realized. A still more extraordinary foreshadowing of one of the most recent improvements of the Electric Telegraph was the transference of written letters from one place to another by electric agency. This is said to have been accomplished by Kircher, who, in his "Prolusiones Magneticæ," describes, though very vaguely, the mode of operation. But even admitting that there were substantial foundations for these imaginary phantasms, that would not in the least detract from the merit of those who, following closely the footsteps of scientific discovery, have successfully applied the principles unfolded by the investigations of others, and by their own assiduous researches. Thus, whilst steam navigation was facilitating the means of intercourse over rivers and seas, and whilst railways and locomotive engines served to bring distant cities within a few hours' journey of each other, another source of power, infinitely more rapid in its action than steam, has been made to transmit intelligence from place to place, and from one country to another, with the speed of lightning.
The plan of making communications by signals has been in operation from time immemorial; the beacon lights on hills having served in ancient as well as in modern times to give warning of danger, or to announce tidings of joy. Such simple signals were not capable of much variety of expression; but even beacon lights might be made to indicate different kinds of intelligence, by multiplying the number of the fires, and by altering their relative positions. It was not, however, till the invention of telegraphs that anything approaching to the means of holding regular communication by signals was attained. The semaphore of the brothers Chappe, of France, invented by them in 1794, was the most perfect instrument of the kind, and was generally employed for telegraphic purposes, until it was supplanted by the Electric Telegraph.
The semaphore consisted of an upright post, having arms on each side, that could be readily extended, at any given angle. The extension of these arms on one side or the other, either separately or together, and at different angles, constituted a variety of signals sufficient for the purposes of communication. The semaphores, erected on elevated points, so as to be visible through telescopes, signalled intelligence slowly from one station to another, till it reached its ultimate destination; and thus—daylight and clear weather permitting—brief orders could be sent from the Admiralty to Portsmouth in the course of a few minutes. But the communication was liable to be interrupted by fogs, as well as by nightfall.
A remarkable instance of the imperfection of sight telegraphs occurred during the Peninsular War. A telegraphic despatch, received at the Admiralty from Portsmouth, announced—"Lord Wellington defeated;"—and then the communication was interrupted by a fog. This telegraphic message caused great consternation, and the utmost anxiety was experienced to learn the extent of the supposed disaster. When, however, the fog dispersed, the remainder of the message gave a completely opposite character to the news, which in its completed form ran thus: "Lord Wellington defeated the French," &c.
Some better means of transmitting important intelligence was evidently wanted; for not only was the semaphore liable to frequent interruptions by the weather, but its action was very slow, and the frequent repetitions from station to station increased the risk of blunders.
The instantaneous transmission of an electric shock suggested the means of communicating with greatly increased rapidity; and when it was ascertained, by experiments made by Dr. Watson at Shooter's Hill, in 1747, that the charge of a Leyden jar could be sent through a circuit of four miles, with velocity too great to be appreciable, the practicability of applying electricity for conveying intelligence became at once apparent.