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Skickas inom vardagar. This work has been selected by scholars as being culturally important and is part of the knowledge base of civilization as we know it. This work is in the public domain in the United States of America, and possibly other nations. Within the United States, you may freely copy and distribute this work, as no entity individual or corporate has a copyright on the body of the work.

This innovation, which is due to Mr. Clark M. The weight, in proportion to the length, is less, and the whole is therefore more manageable which is a very important fact in the difficult operation of laying down.

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This method, also, offers great facilities for repairing any damage that may happen to the cables, for every wire being independent of all the others, can be overhauled in its entire length, without useless labour, or fear of disturbing messages which may be passing on the perfect wires. This latter event has been partially guarded against by Mr. Clark, by twisting all the cables together into one, near the shore, upon shoals, in anchorage waters, and other places where such accidents are probable. The two methods do not materially vary in expense. The actual laying down of a telegraph cable offers interesting details, which require to be treated in a separate Paper, based upon the account of some great enterprise, such as the Atlantic Cable; the Author has, therefore, preferred omitting, on the present occasion all notice of these operations.

The passage of electricity by submerged wires, as compared with that by suspended wires of the same conducting capacities, presents phenomena well worthy of study, and which deserve to be minutely considered, before undertaking the construction of submarine lines of very great extent.

If one pole of a battery be connected with the earth, and the other pole be connected, through a galvanometer, or coil, with either end of a submerged wire, a rush of electricity into the wire will instantly take place, and be noted by a deflection of the galvanometer needle. But soon, although contact with the battery be continued, the deflection will cease, except such few degrees as are due to leakage, or the actual conducting power of the gutta percha.


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If the battery pole be then removed, and the end of the water wire put to earth, the electricity will rush out of the wire, and the galvanometer needle will be deflected in the opposite direction. These effects of charge are not observed in a suspended wire, in which the degree of deflection, owing to defective insulation, is alone shown, and that immediately. Professor Faraday in a lecture at the Royal Institution, explained how this takes place. Upon contact with the battery-pole, the copper wire becomes charged statically, with that electricity which the pole can supply, [8] and acts, through the gutta percha, by induction, without which induction it cannot itself become charged, [9] producing the contrary state of electricity in that film of water surrounding the gutta percha.

There being no outer coating to the suspended wires, representing the earth, or the water in the case of a submerged wire, these effects cannot take place. A slight momentary charge might, possibly, be detected upon a long, well insulated, suspended wire, owing to the fact of its being opposed throughout its distance to the surface of the earth; but from the distance between the inductric and inducteous surfaces, it would certainly be infinitesimally small.

A much more important difference exists, with regard to time, in the conducting powers of submerged and suspended wires.

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Professor Wheatstone, who was the first to measure the velocity of an electric current, stated, in , that it travelled through a copper wire, suspended in a room, at the rate of , miles in a second. Thus, if the ends of a conducting wire be connected with the inside and the outside coatings of a Leyden battery, and be so employed to discharge a jar, it will be noticed, that the striking point will be considerably shorter than when the wire is used alone.

This is caused by the tension of the electricity being lowered by the lateral induction. In the submerged wires, also, the induction consequent upon charge, lowers the intensity of the current, and consequently the discharge, or conduction, requires a longer time. The following is a table of the measured velocities of electricity upon metallic conductors, given by several scientific men.

It will be understood from what has been previously said, that notwithstanding the great difference in the results, it is perfectly possible, that the figures given for each experiment may be correct; the disparities being due to the difference of tension, or intensity of the current, occasioned by lateral induction, battery power, or, perhaps, to other causes.

Latimer Clark states, that he experimented with great care on one thousand miles of submerged wire, with different battery powers, varying from one to one hundred pairs of plates; and that he found the velocity of the current in every instance to be identical, - about one thousand miles per second. The wires experimented upon in the last case were eight in number, and each was about two hundred miles in length; they formed the underground line of telegraph between London and Manchester, belonging to the Electric Telegraph Company.

It will be seen, that when the wires were looped together in couples at Manchester, a series of distances of four hundred, eight hundred, twelve hundred, and sixteen hundred miles could be combined in the London office. A galvanometer was placed at each junction of the several loops, so that the passage of an electric wave at that particular point might be noted.

A similar galvanometer was also placed between the battery and the wire, or what is termed on short circuit. Upon establishing contact with the battery, the needle of the first instrument, separated from it by only a few feet of wire, was instantly deflected; after an appreciable space of time the second was affected; then the third; and so on, each in succession, to the last, distant sixteen hundred miles from the battery, in which the deflection took place about two seconds later than in the first. So long as the current was continued, a constant deflection was shown by all the galvanometers, varying according to the leakage upon the line.

When the battery was disconnected, the first instrument immediately fell to zero, the others following in succession, but the farthest did not resume its vertical position until upwards of four seconds after the first: thus showing a current flowing out at one end of the wire, while none was flowing in at the other end. It was found, that by a short connection of the battery, the passage of a wave could be traced along the wire, each needle, in turn, deflecting, and resuming its neutral position, before the succeeding one was influenced.

Again, if after establishing contact with the battery, and then breaking it, the end was connected with the earth, a portion of the electricity in it rushed back again, and deflected the nearest needles in the reverse direction. This resulted from the wire discharging itself at both ends into the earth. In this manner also, by rapidly making and breaking the battery contact, and then connecting with the earth, a current could be sent along the wire through one, or more instruments, and then be recalled, before it reached the other coils; showing how signals may be sent by a perfectly insulated wire, which although good and legible at one end, never arrive at the other.

None of these effects, as to time, are visible upon a suspended wire of similar length, the signals in the first and last instruments appearing to be simultaneous. A theoretic, although inappreciable, period, does undoubtedly elapse, in the passage of a current, but it cannot be measured by the eye with the above apparatus, and no charge can be noticed. In another experiment, made with the same wires, three of the galvanometers were replaced by steel points, and the current was made to pass through a strip of paper, soaked in ferro-prussiate of potassa, and thus to trace its passage in lines of prussian blue.

A seconds clock also, connected with an independent battery, was arranged to make a dot upon the paper at every vibration of the pendulum. Four rows, or lines, of marks were thus produced, one under the other, the first representing seconds of time, and the others showing the presence of electricity at points upon the wire distant four hundred, eight hundred, arid sixteen hundred miles respectively from the battery.

A current was sent along the wire during five seconds.

The result is shown in Fig. This difference of velocity upon the same wire is due, as before stated, to the lateral induction. In the last-mentioned distance, sixteen hundred miles , the Leyden arrangement was of the enormous extent of , square feet internal, and , square feet external coating; represented respectively by the surfaces of copper wire, and of the film of moisture surrounding the gutta percha.

The small difference observable in the time of discharge of the wire eight hundred miles in length, and that of sixteen hundred miles in length, is probably due to the fact, that the last eight hundred miles was not so well insulated as the first, and that, consequently, the current had an easier mode of escape into the earth. A current upon a long submerged wire, when recorded by the decomposing process, shows first, a mere point, which gradually increasing to a maximum thickness, remains unaltered until the battery is cut off, when it gradually diminishes to nothing.

This proves, that power is consumed in exerting the lateral induction; then notifies the equal tension of the battery and induced currents, and finally shows the gradual discharge of the wire. Although a pretty and valuable experiment to the philosopher, this is a great obstruction in the working of telegraphs: what is sent as a dot, is produced at the other end of the line in the form of a double wedge Figs. It will be observed, that the discharge invariably occupies a longer time than the charge; and since no subsequent signal can be made perceptible, until the wire is free, it follows that, in signalling, this time must be allowed to elapse between each wave and the next, deducting such lesser time as the following wave will require to reach its destination.

In other words, the greatest speed, with which successive intermittent waves, in the same direction, can be received upon a submerged wire, is the time of discharge, less the time of charge, for a submerged wire of that particular length. For instance, from the above tables, intermittent signals along a submerged wire, could not be distinguished at a distance of eight hundred miles, unless a period of discharge 4.

In actual practice this speed is very considerably increased, by employing an instrument, first invented by the Author, and afterwards patented and improved by Mr.

Underground Transmission Lines

Cromwell Varley, which reverses the current with every signal sent, and so enables the wire to discharge itself quicker. The difference in the working of electric telegraphs upon suspended and submarine wires, will now be evident.

leondumoulin.nl: Design and Construction of the IRT: Electrical Engineering (Kimmelman)

All electric telegraphs in actual use, depend for their signals upon a quick succession of waves. Others, such as needle instruments, depend upon the number and their respective direction. Time, therefore, is an important element in all, though less so in needle instruments, than with others. There appears to be no practical limit to the speed of the transmission of intermittent waves, upon a suspended wire.

Upon submerged wires, on the other hand, as has been previously shown, the transmission is rigorously restricted as to time, according to the length of the line; and upon submarine and subterraneous wires, as at present constructed, a certain maximum of work only can be done, in a certain time; and by no mechanical contrivance at present known, can this limit be passed, so long as the condition of the wires remains unaltered.

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It is very possible, that upon a submarine line between Ireland and America, one word with another, including the constant repetition of illegible signals that would be necessary, would occupy upwards of a minute in transmission, and consequently that each despatch of twenty-five words, with the code signals, would need about half an hour: [14] thus making forty-eight despatches of twenty words each per diem, the limit for each wire.

However, since writing the above, the Author has been informed, that it has been proved by experiment, that reverse currents may travel, like a wave, through a wire, one after another; so that the American wire might hold two, or more, complete signals in it at the same instant, and thus augment the speed of working twice, or thrice, as compared with the rate of any one given wave. It is not until a line is prolonged to six, or eight hundred miles, that the effects of the charge begin to be seriously inconvenient. Upon all the submarine lines in existence, it is very evident;but even upon the longest yet constructed, it is not sufficient to be of great annoyance.

Messages are sent direct from London to the Hague, a distance of two hundred and thirty miles, including one hundred and twenty miles of cable submerged in the Northern ocean, and twenty miles of subterranean wires beyond Ipswich, at the usual rate of twenty words per minute. It is probable, that the speed of transmitting intelligence upon long submarine lines, will be increased by the ingenuity and invention which characterise the present day; but it is evident, that there will always be some limit of possibility, so long as lateral induction can occur. The Paper is illustrated by a series of Diagrams, from which the woodcuts Figs.

The discussion upon the Paper, No. Window, occupied both evenings, to the exclusion of any other subject. Window said, he had only referred, in the Paper, to the two kinds of submarine cables at present employed, — the simple cable, composed of one wire in each non-conducting envelope, a certain number of them being laid down side by side, so that in case of a casualty occurring to one wire the others might be made use of;—and the compound cable, wherein several wires were covered by one envelope of iron wire. He had alluded to the advantages offered by the simple cable, and this opinion, which was written some months back, had been confirmed by the recent casualties in the Channel.


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During the late gales, the Calais cable, which was of the compound kind, being torn asunder by the anchor of a vessel, there had ensued considerable inconvenience, until the transit of the messages could be arranged by another route; whereas the simple cables, although partially injured, had never ceased to be capable of conveying messages. He did not mean to say, that the simple cable would be the best for the connecting link between the west point of Ireland and the United States;but the case was worth consideration, at the outset of so important an undertaking.

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It had not been his object to disparage the attempt to convey telegraphic messages to America, nor did he mean to say, that the speed would be so slow as to be a bar to profit; but he had given his impressions, derived from experiment, chiefly with the view of eliciting information, from those who had better opportunities of investigating the subject. Charles Bright remarked, that some additions were necessary to render the Paper a complete report of the progress of submarine telegraphy up to the present time. The proportionate strength and weight of the different cables, and their construction; the depth and character of the bottom at the various sites, and the manner of paying out, as also some information as to the power used in the experiments recorded in the tables, should have been given.

The proportions between the power of the current and the different lengths and kinds of wire should, likewise, have been examined. The chief point suggested for discussion, was the difficulty of working, at such a rate as should be commercially successful, through such a length of cable as that now being constructed to connect Europe with America. There was reason to believe, that the effects of the phenomena of induction and retardation were exaggerated. The electrical conditions of an underground wire coincided with those of a submarine wire. It was true, that electric currents, employed in the usual way, with the common needle and recording instruments, were so retarded, that if worked quickly the signals were confused, or blended together; but this could be effectually dealt with.