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may obviously obtain all the signals requisite to express the letters and numerals.

Such is, in general, the nature of the signals adopted in the electric telegraphs in ordinary use in England, and in some other parts of Europe.

It may aid the conception of the mode of operation and communication if we assimilate the apparatus to the dial of a clock with its two hands. Let us suppose that a dial, instead of carrying hands, carried two needles, and that their north poles, when quiescent, both pointed to 12 o'clock.

When the galvanic current is conducted under either of them, the north pole will turn either to 3 o'clock or to 9 o'clock, according to the direction given to the current.

Now, it is easy to imagine a person in London governing the hands of such a clock erected in Edinburgh, where their indications might be interpreted according to a way previously agreed upon. Thus, we may suppose that when the needle No. 1. turns to 9, the letter A is expressed; if it turns to 3, the letter B is expressed. If the needle No. 2. turn to 9 o'clock, the letter C is expressed; if it turn to 3, the letter D. If both needles are turned to 9, the letter E is expressed; if both to 3, the letter F. If No. 1. be turned to 9, and No. 2. to 3, the letter G is expressed; if No. 2 be turned to 9, and No. 1. to 3, the letter H, and soforth.

It may be presumed that there can be but little difficulty in conceiving how, by practice, two persons may communicate with each other by such means, almost, if not altogether, as rapidly as they could write and read.

But a difficulty will doubtless suggest itself to the intelligent and inquisitive reader. It will be asked, whether a sentinel must be kept ever on the watch to observe when a message is coming? for as the hands of our clock do not speak, notice could only be received of a coming message by the incessant vigilance of an observer.

Would it not, however, be admirable if we could attach to this clock a striking apparatus, which should address the ear the moment a message is

about to be sent, and which should, as it were, awaken the attention of the person on duty?

Such an expedient has, in fact, been contrived. The person in London who desires to communicate a message to the telegraphic agent at Edinburgh can actually make the clock strike at his will, and thus command attention.

The manner in which this is accomplished is as admirable by its simplicity and efficiency as that which we have just described.

The quality resorted to in this case is the last of those we have mentioned above, namely, the power to impart the magnetic virtue at will to soft iron.

One of the wires conducted from London passes into the chamber of the telegraphic apparatus at Edinburgh, where it is connected with a coil of wire which envelopes a rod of soft iron. The ends of this rod, which has the form of a horse-shoe, are placed in contiguity, but not in contact, with the detent of a striking apparatus like an alarm-bell.

When a message is about to be sent from London, this bell-wire is put in communication with the galvanic trough in London. Immediately the subtle fluid flows along the wire and converts the horse-shoe rod at Edinburgh into a powerful magnet.

The attractive power which it thus suddenly receives irresistibly draws towards it the detent of the alarum, and lets go the bell, which continues to ring until the agent of the telegraph at Edinburgh answers the demand of the messenger from London, and tells him he is attentive. Then the London communicator withdraws the galvanic current from the bell-wire, the horseshoe at Edinburgh is instantly deprived of its magnetic virtue, the detent flies back to its place by the action of a spring, and silences the bell.*

In the practical arrangement of electric telegraphs, constructed on this principle, the magnetic needles are placed vertically and not horizontally, as in the mariner's compass, and they are kept, when not affected by the current, in the vertical position, by laying two needles having their poles at opposite ends, one upon the other, by which means the polarity of the

Railway Economy, by Dr. Lardner, pp. 352-5. VOL. XXXVI.-NO. CCXI.

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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.

Besides the transmission of private despatches, stations have been es

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

news.

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 coudenses 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

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which business has been done. prices of the French funds for the day preceding are usually annexed, and the state of the London wind and weather at that hour.

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Early in the morning the instrument boys are to be seen greedily devouring (for, with the curiosity, eagerness, and enthusiasm of youth, they appear to take great interest in their duties) the various matters which from all quarters at once are imparted to them.

"One has just received intelligence by telegraph from Ely, announcing the result of the Lynn election. Another a copy of a Moniteur extraordinary, containing the first message of the President of the French Republic to the President of the National Assembly.

"Another, that 'Stewart's and Hetton's were nineteen and sixpence. Gosforth eighteen shill. Holywell fifteen and sixpence. Hastings Hartley fourteen and ninepence. S Qmarket one hun. fifty one, sold one hun. and three-SQ.

"Market very good-P Q.'

"Another, the following characteristic description of the winds and weather of Old England at nine A.M. :—

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"The above description of our changeable climate, it occurred to us, would not very incorrectly represent the present political state of Europe.

"During the day telegraphic information flashes upon these boys from the Stock Exchange, informing them of prices and closing prices of the funds and principal railway shares. With remarks.'

"From the London cattle market, stating the number and quality of beasts, sheep, calves, pigs. Holland beasts, sheep, calves. Danish beasts. With remarks.'

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.

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"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.

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

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.

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.

The third system, called the Electrochemical telegraph, is also exclusively adopted in the United States, and with the improvement which it has recently received, it exceeds by far in efficiency and power all the other telegraphic arrangements hitherto tried. A memoir on this invention has recently been read before the Academy of Sciences in Paris, of which we shall avail ourselves.

The imperfections of the needle and magnet telegraphs, which this improvement removes, are stated as follows:

"To deflect the magnetic needle from a position of rest, and still more to impart sufficient magnetic energy to soft iron so as produce the necessary effects at the stations of arrival, in the systems above mentioned, a galvanic current of a certain force is indispensable. Lines of telegraphic communication being exposed to local and atmospherical vicissitutes, such a force of the current cannot always be secured. This is especially the case when communications are made to great distances, as for example, 300 miles and upwards.

"Supposing the insulation of the supports of the conducting wire to be perfect, and no accidental disturbances arising from atmospheric influence or local causes to be in operation, the strength of the electric current will nevertheless be influenced by mere distance. When the distance is augmented to a certain extent, the current may become so enfeebled as to be incapable either of imparting the necessary magnetic power to the soft iron, or of deflecting the needles from their position of rest."

It is then shown that various other causes, such as imperfect insulation, atmospheric vicissitudes, &c., are liable to intercept the action of the needle and magnetic telegraphs; and that they sometimes even destroy the coils of fine wire which are used to affect the magnets.

The inventor of the electro-chemical telegraph, Mr. Alexander Bain, a native of Scotland, and formerly a watchmaker in that country, rejects the use of needles and magnets altogether, and relies exclusively on the chemical effects of the electric current. By this means he shows that he can obtain

"1st. Greater economy and simplicity in the original construction, and in the permanent maintenance and management of the apparatus;

"2nd. Increased celerity and certainty, and less liability to error in the transmission of communications."

The mode of construction and operation of the electro-chemical telegraph is as follows:

"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.

"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."

The metallic desk on which the paper is placed is circular, and about twenty inches diameter.

"It is fixed on a central axis, with which it is capable of revolving in its own plane. An uniform movement of rotation is imparted to it by means of a small roller, gently pressed against its under surface, and having sufficient adhesion with it to cause the movement of the disk by the revolution of the roller. This roller is itself kept in uniform revolution by means of a train of wheelwork."

The point of the wire, which may be considered as a pen, is gently pressed on this paper. When the current passes, it leaves a blue trace; when the current is interrupted, it leaves no trace.

It is clear, therefore, that by alternately transferring and interrupting the current, such a pen will leave on the paper a succession of lines and dots in any desired combination, precisely similar to those already described in the case of the American system of magnetic telegraph.

But the prominent feature of this system, which confers on it an immeasurable superiority over all which preceded it, is the extraordinary celerity of which it is susceptible. We have already stated that, in the experiments made with this apparatus before the Committees of the Institute and the Legislative Assembly at Paris, despatches were sent along a thousand miles of wire, at the rate of nearly 20,000 words an hour.

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