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system is neutralised, and then a small excess of weight given to one end of the combined needles is sufficient to keep them in the vertical position, when fixed upon an horizontal axis.
In this manner they are fixed upon the dials already described, being free to turn on their axis when affected by a deflecting force sufficiently strong to overcome the small excess of weight just mentioned.
This is the principle of the telegraph now used generally in England. The entire system, except the lines which follow the course of the South-Eastern Railway, is in the hands of a company incorporated by act of parliament, and who, therefore, hold a virtual monopoly of the chief part of the telegraphic business of the kingdom.* A central station is established in London, in Lothbury, near the Bank of England. The lower part of the building is appropriated to the reception of orders and messages. A person desiring to forward a message to any part of England, connected with London, by the wires, writes his message on a sheet of letter-paper, provided for the purpose, and prepared according to a printed form, having the names and address of the writer, and of the party to whom the message is communicated, in blank spaces assigned to them, together with the date and hour at which the message is des patched. The answer is received, accompanied by the date and hour at at which the message arrived, and at which the answer was despatched.
The tariff of charges for transmission of telegraphic messages differs very much, according to the destination of the message, and is not strictly regulated by distance.
It is found that by practice the operators of the telegraphic instruments, constructed on this system, are able to communicate about twenty words per minute, when they work with two needles and two conducting-wires, and at the rate of about eight words per minute when working with a single needle.
tablished by the company in the chief towns of the kingdom, whence and whither intelligence is transmitted from time to time during the day, so that there is thus kept up a never-ceasing interchange of news over the entire extent of that net-work of wires which has overspread the country. At each of these stations public subscriptionrooms have been established, in which are posted from hour to hour as they arrive, during the day, the public news, which are known to be of most interest to the local population, such as the money market, shipping intelli. gence, sporting intelligence, quotations of the commercial markets at all chief places, and parliamentary and general
Besides the transmission of private despatches, stations have been
We take the following description of the routine of business in this department of the Central Telegraphic Office at Lothbury, from a popular author already quoted :
"At seven in the morning the superintendent of the former department obtains all the London morning newspapers, from which he condenses and despatches to the several electric stations the intelligence he considers most useful to each. The local press of course awaits the arrival, and thus by eight o'clock A.M. a merchant at Manchester receives intelligence which the rails can only bring at a quarter before two, and which cannot by rail reach Edinburgh till half-past nine P.M.
"To Glasgow is transmitted every evening detailed intelligence for immediate insertion in the North British Daily Mail,' giving everything of importance that has occurred since the first edition of the London papers. Similar intelligence is despatched to papers at Hull and Leeds.
"By this rapid transmission of intelligence, the alternations in the prices of the markets at Manchester, &c. &c., being almost simultaneous with those of London, the merchants of the former are saved from being victimised by the latter. It is true that by great exertions prior intelligence may electrically be sent by private message; but as the wary ones cautiously wait for the despatch of the Telegraph Office, it has but little effect.
"At one o'clock information is sent to all the electric reading-rooms of the London quotations of funds and shares up to that hour, thus showing the actual prices at
A Bill is now before Parliament to incorporate a competing company.
"From the meat market, stating 'the prices of every description of meat, with remarks.'
"Also similar returns from all the other markets we have enumerated.
"As fast as this incongruous mass of intelligence arrives, it is, in the mode already described, transcribed in writing to separate sheets of paper, which are without delay, one after another, lowered down to the superintendent of the Intelligence Department,' by whom they are rapidly digested for distribution either to the whole of the Company's reading-room stations, or for those lines only
which any particular species of information may partially interest-such as corn-markets requiring corn intelligence; seaports, shipping news, &c. &c.
"As quickly as these various despatches. are concocted, the information they respectively contain reascends through the lift,' or wooden chimney, to the instrument department, from whence it is projected, or rather radiates, to its respective destination; and thus in every one of the Company's reading-rooms throughout the kingdom there consecutively appears, in what would until very lately have been considered magic writing upon the walls, the varied information which had only reached London from all points of the compass a few minutes ago!"
It will, however, be asked how despatches can be transmitted to various stations along the extensive lines of telegraphic communication which have been established, unless a separate and independent wire be appropriated to each station, which would be manifestly impracticable.
The answer is easy: At each station the conducting wire is carried from the main wire through the instrumentroom of the station, and passing through the instrument, is carried out again and continued along the line by the posts as usual. It is, therefore, apparent that every message despatched from any station must affect the instruments at all the other stations; and if desired, can be interpreted and written out at them all. It is therefore necessary to provide means by which this needless labour shall not be imposed upon the telegraphic agents, and so that it may be at once known for what station or stations each message is intended.
This is accomplished by the following expedient:-The agent at the station from which the message is despatched first sends the current along the bell-wire. By the means already described, bells are then rung at all the stations, and the attention of the agents is called. The name of the station for which the despatch about to be forwarded is intended, is then transmitted, and appears upon the dials at all the stations. The agents at all the stations, except that to which the despatch is addressed, are then released from further attention, and the agent at the station to which it is addressed interprets the signs as they are successively transmitted, and reduces the message to writing.
It will be seen, therefore, that every message which is despatched, no matter for what station it is intended, is in fact, sent to all the stations which the wire passes.
The telegraphs established in England, which alone we have here explained, are constructed on the needle system, that is to say, the signals are made by the deviations of magnetic needles, from their position of rest produced by electric currents passing around them.
Telegraphs depending on the second and third principles adverted to above, have been brought into extensive use in America, the needle system being in no case adopted.
To explain the construction and operation of telegraphs depending on the power of magnetism on soft iron by an electric current, let us suppose a small lever formed of steel, and balanced on a point. At one end of this lever let a point be formed, so as to constitute a pencil or style. Under the other end let a horse-shoe of soft iron be placed at such a distance, that when it shall receive the magnetic virtue from the electric current, the lever will be drawn to the horse-shoe; and let it be so arranged, that when the horse-shoe shall lose its magnetic virtue, the pencil will fall.
Now suppose that immediately above the pencil is placed a small roller, under which a ribbon of paper passes, which receives a slow progressive motion from the roller. Whenever the pencil is raised by the magnet, its point presses on the paper which moves over it, and if it be kept pressed upon it for any time, a line will be traced. If the pencil be only momentarily brought into contact with the paper, a dot will be produced.
It is clear then, that if we have the power of keeping the pencil for any determinate time in contact with the paper, or of making it only momentarily touch the paper, we shall be enabled to produce lines and dots in any required succession; and by suspending the action of the pencil, we can leave blank space of any desired length between such combinations of lines and dots.
system, let us suppose a person at New York desirous of sending a message to New Orleans. A wire of the usual kind connects the two places.
The end at New Orleans is coiled round a horse-shoe magnet. The end at New York can be put in communication with the galvanic trough at the will of the person sending the message. The instant the communication is established, the horse-shoe of soft iron at New Orleans becomes magnetic, it attracts the small lever, and presses the pencil against the paper.
The moment the operator at New York detaches the wire from the trough, the horse-shoe at New Orleans loses its magnetic power, and the pencil drops from the paper. It is clear, then, that the operator at New York, by putting the wire in contact with the trough, and detaching it, and by maintaining the contact for longer or shorter intervals, can make the pencil at New Orleans act upon the paper, as already described, so as to make upon it dots and lines of determinate length, combined in any manner he may desire, and separated by any desired intervals.
It is easy, therefore, to imagine how a conventional alphabet may be formed by such combination of lines and dots. To explain the operation of this
In a word, the operator at New York can write a letter with a pencil and paper which are at New Orleans.
Provisions in such an arrangement are made, so that the motion of the paper does not begin until the message is about to be commenced, and ceases when the message is written. This is easily accomplished by the same principle as has been already described in the case of the bell, which gives notice to the attendant in the European telegraph. The cylinders which conduct the band of paper are moved by wheel-work, and a weight properly regulated. Their motion is imparted by a detent detached by the action of the magnet, and which stops the motion when the magnet loses its ,virtue.
"Let a metallic desk be provided, corresponding in magnitude with the sheet of paper, and let this metallic desk be put in communication with a galvanic battery so as to form its negative pole. Let a piece of steel or copper wire, forming a pen, be put in connexion with the same battery so as to form its positive pole. Let the sheet of moistened paper be now laid upon the metallic desk, and let the steel or copper point, which forms the positive pole of the battery, be brought into contact with it. The galvanic circuit being thus completed, the current will be established, the solution with which the paper is wetted will be decomposed at the point of contact, and a blue or brown spot will appear. If the pen be now moved upon the paper, the continuous succession of spots will form a blue or brown line, and the pen being moved in any manner upon the paper, characters may be thus written upon it as it were in blue or brown ink."
"Let a sheet of writing paper be wetted with a solution of prussiate of potash, to which a little nitric and hydrochloric acid ave been added.
We shall now explain the means by which this extraordinary feat is accomplished.
"A narrow ribbon of paper is wound on a roller, and placed on an axis, on which it is capable of turning, so as to be regularly unrolled. This ribbon of paper is passed between rollers under a small punch, which, striking upon it, makes a small hole at its centre. This punch is worked by a simple mechanism so rapidly, that when it is allowed to operate without interruption on the paper passing before it, the holes it produces are so close together as to leave no unperforated space between them, and thus is produced a continuous perforated line. Means, however, are provided by which the agent who superintends the process can, by a touch of the finger, suspend the action of the punch on the paper, so as to allow a longer interval to elapse between its successive strokes upon the paper. In this manner a succession of holes are perforated in the ribbon of paper, separated by unperforated spaces. The manipulator, by allowing the action of the punch to continue uninterrupted for two or more successive strokes, can make a linear perforation of greater or less length on the ribbon; and by suspending the action of the punch, these linear perforations may be separated by unperforated spaces.
"Thus it it is evident, that being provided with a preparatory apparatus of this kind, an expert agent will be able to produce on the ribbon of paper as it unrolls, a series of perforated dots and lines, and that these dots and lines may be made to correspond with those of the telegraphic alphabet already described.
"Let us imagine then the agent at the station of departure preparing to despatch a message. Preparatory to doing so it will be necessary to inscribe it in the perforated telegraphic characters on the ribbon of paper just described.
"He places for this purpose before him the message in ordinary writing, and he transfers it to the ribbon in perforated characters by means of the punching apparatus. By practice he is enabled to execute this in less time than it would be requisite for an expert compositor to set it up in common printing type.
"The punching apparatus for inscribing in perforated characters the despatches on ribbons of paper is so arranged, that several agents may simultaneously write in this manner different messages, so that the celerity with which the messages are inscribed on the perforated paper may be rendered commensurate with the rapidity of their transmission, by merely multiplying the inscribing agents.
"Let us now imagine the message thus completely inscribed on the perforated ribbon of paper. This ribbon is again rolled as at first upon a roller, and it is now placed on
an axle attached to the machinery of the telegraph.
"The extremity of the perforated ribbon at which the message commences is now carried over a metallic roller which is in connexion with the positive pole of the galvanic battery. It is pressed upon this roller by a small metallic spring terminating in points like the teeth of a comb, the breadth of which is less than that of the perforations in the paper. This metallic spring is connected with the conducting wire which passes from the station of departure to the stations of arrival. When the metallic spring falls into the perforations of the ribbon of paper as the latter passes over the roller, the galvanic circuit is completed by the metallic contact of the spring with the roller, but when those parts of the ribbon which are not perforated pass between the spring and the roller, the galvanic circuit is broken and the current is interrupted.
"A motion of rotation, the speed of which can be regulated at discretion, is imparted to the metallic roller by clock work, so that the ribbon of paper is made to pass rapidly between it and the metallic spring, and as it passes this metallic spring falls successively into the perforations on the paper. By this means the galvanic circuit is alternately completed and broken, and the current passes during intervals corresponding precisely to the perforations in the paper. In this manner the successive intervals of the transmission of the current are made to correspond precisely with the perforated characters expressive of the message, and the same succession of intervals of transmission and suspension will affect the writing apparatus at the stations of arrival in the manner already described.
"Now there is no limit to the speed with which this process can be executed, nor can there be an error, provided only that the characters have been correctly marked on the perforated paper; but this correctness is secured by the ribbon of perforated paper being examined after the perforation is completed, and deliberately compared with the written message. Absolute accuracy and unlimited celerity are thus attained at the station of departure. To the celerity with which the despatch can be written at the station of arrival, there is no other limit than the time which is necessary for the electric current to produce the decomposition of the chemical solution with which the prepared paper is saturated."
Such are the means by which these extraordinary effects are produced; and we have been the more willing to give them with some detail, because the memoir from which they are obtained is still unpublished, and the reader would in vain seek for this information elsewhere.