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CHAPTER XIV.

THE ELECTRIC TELEGRAPH.

Fire Beacons-The Semaphore- First Idea of Application of Electricity-Messrs. Wheatstone and Cooke-Their Experiments-Description of their Patent-Apparatus employed in the Construction of the Electric Telegraph-The Battery-The Electric Fluid "-The Wires, and Mode of Fixing them-Proposal to attach the Wires to Trees-A Negro Explanation-Effects of Thunder Storms on the WiresUse of the Telegraph in Working a Railway-The Idea that Birds are injured by standing on the Wires shown to be a Fallacy-Use of Telegraph in regulating Time -Anticipations.

HE importance of means of rapid and efficient communication between distant places is sufficiently obvious, and was recognised at a very early period. The simplest and most significant of these were beaconfires, by lighting which, some intelligence, whether for good or evil, might be communicated over an entire country in a comparatively limited space of time. Illustrations of the use of fire signals are

abundant. Macaulay alludes to them in his Armada.

"Forthwith a guard at every gun was placed along the wall;
The beacon blazed upon the roof of Edgecumbe's lofty hall.

From Eddystone to Berwick bounds, from Lynn to Milford Bay,
That time of slumber was as bright and busy as the day;
For swift to east, and swift to west, the ghastly war-flame spread,
High on St. Michael's Mount it shone: it shone on Beachy Head.
Far on the deep the Spaniard saw, along each southern shire,

Cape beyond cape, in endless range, those twinkling points of fire."

Reference is also made to this means of communication in the "Lay of the Last Minstrel," where the approach of the English from the border stations along "height, and hill, and cliffe" is announced::

Till high Dunedin the blazes saw,
From Soltra and Dumpender Law;
And Lothian heard the regent's order,

That all should boun them for the border."

In a note illustrative of this description, Sir Walter refers to an enactment of the Scottish Parliament, in 1455, which directs that one bale, or faggot, shall be the notice of the "approach" of the English in any manner; two bales, that they are "coming indeed;" and four bales blazing beside each other, to say that are "coming in great force."

Various means were employed for the despatch of intelligence by more systematic agency. The Admiralty transmitted a great number of their orders by the semaphore. This was an apparatus provided with arms, boards, fans, or shutters, which by means of shutters could be placed in any desired position in relation to one another, and to the person viewing them. The semaphore establishments were situated on eminences, in order that they might be seen at a distance, while the attendants were supplied with all the necessary facilities for deciphering the signals as fast as they were transmitted. These means of communication are worthy of notice here, as we shall find, that though the Electric Telegraph is a most important agent in the management of a railway; yet that the semaphore system is preserved in both its forms in the signal apparatus of our lines.

The great efficiency which the Electric Telegraph system has attained, is mainly due to the improvements of Messrs. Wheatstone and Cooke. Mr. Cooke, being in Germany, was invited by Professor Moencke, of Heidelberg, to witness some experiments with a simple apparatus, intended to illustrate the possibility of giving signals by electricity. The impressions then produced upon his mind, were of such a nature, that he devoted himself from that hour to the furtherance of his plan; while he was so aided by his native energy, and ingenuity of mind, that within three weeks of his first receiving the idea, he had constructed, at Frankfort, two galvanometer telegraphs, capable of giving twenty-six signals; added to which was his invention of the detector, by which injuries to the wires are readily traced, and the alarum, to give notice at one end of the telegraph that something is to be communicated at the other. Returning to England, about six weeks after, he occupied the following year in constructing a variety of instruments, and exerting himself to introduce his telegraph on the Liverpool and Manchester Railway. In 1837, he joined Professor Wheatstone in his arrangements, that gentleman having been for some years employed in endeavouring to transmit signals, both by sound and electricity. From that time their operations were carried forward together, and they entered into partnership as proprietors of the patent under which the telegraph is worked.

The positions occupied by these two distinguished individuals, in

reference to electric discoveries, as connected with the purposes of communication, have been well expressed in the words of Sir M. I. Brunel. "While Mr. Cooke is entitled to stand alone, as the gentleman to whom this country is indebted for having practically introduced and carried out the electric telegraph, as an useful undertaking, and Professor Wheatstone is acknowledged as the scientific man whose profound and successful researches have already prepared the public to receive it as a project capable of practical application; it is to the united labours of two gentlemen, so well qualified for mutual assistance, that we must attribute the rapid progress which this important invention has made since they were associated."

In this patent, for which application was made in 1837, the principal points of novelty were the use of a much smaller number of needles to denote all the required signals; the employment of the temporary magnetism excited in the current in soft iron to ring an alarum, by means of suitable machinery; and the reciprocal arrangement by which the invention was made practically available for a long line of communication. The instrument shown in the drawings which were annexed to their specification, was applied on the Great Western Railway, shortly after the date of the patent, and contained five needles, arranged with their axes in a horizontal line. The needles were made to hang vertically, by the addition to one end of the increased weight; and each coil was connected with a long conducting wire at one end, being united at the other with a common rod of metal, which joined together the similar ends of all the coils. The transmission of the electric current took place from the opposite ends of the wires, through two of them at once; that is to say, one of the wires, of which one key was pressed down, served to convey the current from one pole of the battery to the distant instrument, while it returned, by the rod of metal connecting the coils and the second wire, to the battery again. Two needles were in this manner deflected at once; and it will be obvious that the current would pass in opposite directions around their coils, and consequently that their deflections must be in contrary directions. The needles would therefore converge, either above or below their lines of centres, as one or other of the pair of keys belonging to each wire was depressed. Fixed stops were so placed on each side of the needles as to limit their motion, and when resting against them, the needles were parallel to two converging lines, at the point of intersection of which a letter was placed. This was the signal indicated by the movement of the needles. In a similar manner, as lines were drawn diverging from the centre of each axis, mutually crossing one another, a

number of points of intersection were formed, at one of which was a letter or signal. As any of these letters could be indicated by the movements of the needles, any communications could be made with certainty. A plan was also under consideration, for reducing the number of wires, and thus diminishing the complexity of the scheme. The apparatus employed in the construction of the telegraphs may be divided into the following parts:-the generator of the galvanic or electric fluid, the motive, or electro-magnetic arrangement, and the conducting wires. The battery is the motive power of the machine, occupying the same relation to it that the boiler does to the locomotive; for though it can do nothing of itself, yet its work is essential to the whole. It is the fountain of that subtile stream which is popularly known as the "electric fluid." Under the superintendence successively of Galvani, Volta, Cruikshanks, Davy, Wollaston, Roget, and others, the electric generator has reached its present perfection; while the whole has undergone great improvements in its adaptation to the purposes of electric communication by Mr. Cooke, and the gentlemen of whom we shall have to speak. Mr. Cooke found that, while travelling, great inconvenience arose from the spilling of the acid solution used in Smee's batteries, and from this he was led to consider whether the substitution of fine, white sparkling sand, saturated with the diluted acid, would not obviate this difficulty. Experiments having confirmed the truth of the supposition, the change was effected, and it was subsequently found so advantageous, that the same method was tried in the permanent batteries, and the issue was equally satisfactory. The generator now usually employed resembles in its principal features the one known as Wollaston's trough, and it is so arranged, that the series of plates of copper and amalgamated zinc, provided for the evolution of the galvanic fluid, admit of being placed in a corresponding series of cells, filled with well-washed and dry sand. To put these instruments into action, it is only necessary slightly to moisten the sand with diluted sulphuric acid; and they are stated to be very constant in their action, being found to work during periods varying from two to five months, with only small occasional additions of the acid solution to supply the waste produced by evaporation and chemical absorption. The sand, too, appears to check injurious rapidity of action, and, at the same time, to prevent the separation of the sulphate of copper and zinc, formerly held suspended in the fluid.

The property possessed by the wires of rendering iron magnetic when subject to the galvanic currents, may be illustrated in a simple

manner, by passing copper wire a few times round a glass tube, so as to form a coil, like a bell-spring, taking care that the turns of the wire are nowhere in contact; if the ends of the coil are then connected with the poles of the battery, and a small sewing needle is placed in the glass tube, it will be immediately drawn to the centre, and, if examined, will be found to be permanently magnetic. If, on the other hand, a piece of soft iron wire had been introduced into the glass tube in the place of the steel needle, it would be found to be magnetic only so long as it remained under the influence of the exterior coil of wire,-proving that it is to the magnetising property of the electric current, under a certain form of arrangement, that we owe our motive power; and it is to the varied motions or vibrations of the needles on the face of the dial-plate, produced by this agent, that a form of alphabet has been adopted, by means of which we are enabled to communicate with a person at any distance from us. Till the year 1840, the wires were covered with cotton, and insulated by coating them with shell-lac, resin, or pitch; and they were laid down in pipes of wood or iron. It was, however, subsequently found that, under existing circumstances, the advantages would be equal, and the expense greatly diminished, if the wires were suspended on poles in the open air. By the adoption of this plan, superior isolation, greater permanency, and increased facility of repair would result; and while the cost of the original plan was estimated at £300 per mile, it is reduced, in the improved system, to £150. The ordinary method of proceeding, in the establishment of the telegraph, has been, first, to fix firmly in the ground, at every five or six hundred yards, strong posts of timber, sixteen or eighteen feet high, eight inches square at bottom, and tapering off to six or seven inches at the top, fixed into stout sills. A coil of iron wire is then placed upon a reel, carried on a handbarrow, and one end being attached to the winder at one draw-post, the wire is extended to the adjoining draw-post, and fixed to a winding apparatus there; and then, by turning the pin of a ratchetwheel with a proper key, the wire is tightened, so that the greatest accuracy may be attained in drawing the wire, until they are as nearly as possible parallel to each other.

At each quarter of a mile a stouter post is placed, to bear the winding or straining apparatus. This consists of a simple windingwheel, connected with a ratchet-wheel and clink, to prevent its recoil after the wire has been once put up. The intermediate posts or standards merely support the wire, having no influence on their tension-this being performed by the winding apparatus. When,