Submarine telecommunication cable

“ The engineers were fast learning the rigorous conditions of submarine telegraphy; in its essentials the Dover-Calais line continues to be the type of deep-sea cables to-day. The success of the wire laid across the British Channel incited other ventures of the kind. Many of them, through careless construction or unskilful laying, were utter failures. At last, in 1855, a submarine line 171 miles in length gave excellent service, as it united Varna with Constantinople; this was the greatest length of satisfactory cable until the submergence of an Atlantic line. ”

“ According to recent statistics, the North Atlantic Ocean is now crossed by no less than 17 cables, the number of cables all over the world being 2937, with a total length of 291,137 nautical miles.
Before describing the actual working of a submarine cable, a few words on cable-laying may be of interest. Before the cable-ship starts, another vessel is sent over the proposed course to make soundings. Galvanized steel pianoforte wire is used for sounding, and it is wound in lengths of 3 or 4 nautical miles on gun-metal drums. ”

“ Such a cable may work at the regular line voltage, or a transformer station may be established on one side or on each side of the body of water. Even where it is possible to span a body of water with a transmission line, the cost of the span and of its supports may be so great that a submarine cable is more desirable. A moderate increase in the length of a transmission line in order to avoid the use of a submarine cable is almost always advisable, but where rivers are in the path of the line it is generally impossible to avoid crossing them either overhead or underneath. ”

“ Owing to the small currents received and to prevent interference from earth currents it is necessary to use a complete metallic circuit. If an overhead line could be employed no difficulty would be experienced in working a distance of over 1000 miles, but a line of this length is impossible—at least in this country—and if transmission is attempted with any other country, a certain amount of submarine cable is essential. ”

“ Twenty-seven years ago the first submarine cable was laid across the Strait of Dover. This was a single copper wire covered in gutta-percha, which parted next day; and the first practicable submarine cable was laid in 1851, on the same route. Since then the progress of ocean telegraphy has been extraordinary ”

“ Countries far apart, and isolated by oceans, have, by means of deep-sea cables, been brought into intimate relation, and made sharers of one another’s intelligence, enterprise, and civilizing instincts. What the overland telegraph has done toward bringing local states and communities into contact, the submarine cable has done for the remote nations.
In form, an ocean cable differs much from the simple wire which constitutes the conductor of an overland or even underground telegraph. ”

“ In all there are more than 150,000 miles of submarine cable under the waters of the globe, and there is a fleet of forty ships, large and small, fitted out solely for the purpose of laying and repairing submarine cables. Nowadays the laying of an Atlantic cable attracts no attention, and the fishing up of a slender rope less than an inch thick from the floor of the ocean, 12,000 or 15,000 feet down, is a thing done a dozen times a year. ”

“ It was in 1851 that an electric cable was actually laid in the open sea, and worked successfully; and the wire which then connected Dover with Calais was beyond question the first important line of submarine telegraph ever attempted. In the year 1850, Mr. Brett obtained a concession from the French Government for effecting this object,—an object regarded at the time as one purely chimerical, and decried by the press as a gigantic swindle. The cable which was made for the purpose consisted of a solid copper wire, covered with gutta percha. ”

“ There are two forces, in fact, pulling against each other through the gutta-percha as a neutral medium,—that is, the electricity in the wire, and the opposite electricity in the film of water immediately surrounding the cable; and to that extent the power of the current in the enclosed wire is weakened. A submarine cable, when in the water, is virtually a lengthened-out Leyden jar; it transmits signals while being charged and discharged, instead of merely allowing a stream to flow evenly along it: it is a bottle for holding electricity rather than a pipe for carrying it ”

“ Before laying a submarine cable between the proposed places it is extremely important to take soundings and otherwise survey the ocean, so as to determine the exact route the cable should take. A cable is too costly to be flung away anywhere on the sea-bottom, and the sea-bottom is sometimes of a very unfavourable character. ”

“ A light cable or unprotected core must therefore be regarded at best as an experiment, with the chances against the successful laying, and still more against its existing as a permanent property.
I have written enough to illustrate that the present submarine cable is not a haphazard idea, but one which has grown out of many failures and thousands of experiments; all the principles of manufacture and laying down have been established by great anxiety and reflection on the part of the able men who gave their energies to this kind of enterprise prior to 1865. ”

“ It may be well believed that the Directors have not decided upon a matter so all-important to success, without availing themselves of the most eminent talent and experience which could be commanded. The practical history of submarine telegraphs dates from the successful submersion of the cable between Dover and Calais in 1851, and advantage has been taken of whatever instruction this history could furnish or suggest. Of the submarine cables heretofore laid down, without enumerating others, the one between Dover and Calais weighs six tons to the mile ”

“ The receiving instruments for working a submarine cable are different from those used in working land-lines. Inasmuch as the current travels full strength, like a bullet, through a land-line, and in the form of an undulation or wave through a cable, so is it necessary to have different kinds of receiving instruments for each. In a land-line powerful currents can be used with impunity, and these can be made, by means of electro-magnetism, to move comparatively heavy pieces of mechanism in giving signals. ”

“ Submarine Telegraphy.—For working long submarine cables the apparatus ordinarily employed on land lines cannot be used, as the retarding effect of the electrostatic capacity of the cable is so marked that signals fail to be recorded except at a very slow speed of working. The transmitted signals or electric impulses, which on a land line are sharply defined when received, become attenuated and prolonged in the case of a long cable, and are unable to actuate the comparatively heavy moving parts of which the land line instruments are formed. ”

“ Instantly a thousand hearts were tortured with fear, lest their loved ones had gone to the bottom of the sea, when the cable reported that the delay was due simply to an accident to her machinery, that would keep her back for a day or two, but that the good ship was safe with all on board. What arithmetic can compute the value of a single message that relieves so much anguish? Thus the submarine telegraph stretched out its long arms under the sea, [Pg 394] to lay a friendly hand on two peoples, and give assurance to both. ”

“ In the French Atlantic cable no current can be detected by the most delicate galvanoscope at America for the first tenth of a second after it has been put on at Brest; and it takes about half a second for the received current to reach its maximum value. This is owing to the phenomenon of induction, very important in submarine cables, but almost entirely absent in land lines. In submarine cables, as is well known, the copper wire which conveys the current is insulated from the sea-water by an envelope, usually of gutta-percha. ”

“ Wires, or stays, as they are called, fore and aft are used to brace and hold the periscope and signal stanchion firm against the force of the water which presses on them when the craft is submerged and under way. The tops of the signal stanchion and the periscope are also braced by a signal halyard, which is simply a wire, or cable, stretched taut between them.
On all modern submarines a wireless aerial is attached to a mast which can be folded down flat on the deck when the submarine is getting ready to make a dive. ”

“ The practical working of a submarine cable differs in many respects from that of a land telegraph line. The currents used in submarine telegraphy are extremely small, contrary to the popular impression. An insulated cable acts like a Leyden jar, in the sense that it accumulates electricity and does not quickly part with it, as does a bare overhead wire. In the case of a very long cable, such as one across the Atlantic, a current continues to flow from it for some time after the battery is disconnected. ”

“ In reply to your inquiries, we beg to state that we should not be willing to manufacture and lay a Submarine Telegraph Cable across the Atlantic, from Ireland to Newfoundland, assuming the entire risk, as we consider that would be too great a responsibility for any single firm to undertake; but we are so confident that these points can be connected by a good and durable cable, that we are willing to contract to do the work, and stake a large sum upon its successful laying and working. ”

“ For six months the guardians of the light are isolated from the world at large, although they have a slender link of communication in the submarine cable. But the storms and stress of winter often rupture this line, and, as the wireless installation is closed down when navigation ceases, the keepers and their families settle down to a silent, weary vigil, knowing nothing of the rest of the world, and all but forgotten by civilization, because an interruption in the cable cannot be repaired until the ice disappears. ”

“ EVENTS FOLLOWING THE CIVIL WAR.
THE ATLANTIC CABLE.
Original
ARLY [318] in October, 1851, the first effort at laying a cable for a submarine telegraph was begun by the United States brig Dolphin, which carried a line of soundings across the Atlantic. At that time there were but eighty-seven nautical miles of submarine cable laid, while now there are nearly 200,000 statute miles. Some of these cables merely connect islands with the main shore, others are thousands of miles long. A cable is laid so far below the surface that neither storms, tides or currents can disturb it. ”

“ The cable was automatically ranged in a compartment between the inner and outer skins, the space being always filled with water. The inboard end of the cable was not shackled; but to prevent its being able to take charge and run out, an indicator was placed on the bulkhead nearest to the cable tier. The amount of chain let go was regulated by a compressor, which was actuated from within the hull by means of levers and cranks, watertight glands being provided to prevent any leakage into the interior of the submarine. ”

“ If it becomes absolutely necessary to reverse the propellers when paying out cable, men paying it out must haul it in taut and keep it above the wheel and clear of it. The planting vessel should not pass nearer than 25 feet to the distribution box boat when cable is leading out from the latter, nor should it pass over any cable, if it can be avoided, if the depth is less than 16 feet. ”

“ Submarine cables have multiplied recently, and almost every ocean flows over the mysterious wires which flash intelligence beneath the rolling waters from point to point of the civilized world. By a telegraph-cable, which is partly submarine, the India Office in Westminster is united with the Governor-General and his Council at Calcutta. ”

“ Other Early Cables.—The success of Crampton’s line gave considerable impetus to submarine telegraphy. Similar enterprises sprung up on all sides; but many failures occurred before these operations came to be regarded as ordinary industrial undertakings. In the course of the following year (1852) three unsuccessful attempts were made to establish telegraphic communication between England and Ireland. In the first—between Holyhead and Howth—the cable was not heavy enough to contend with the rough bottom, and strong currents and disturbances from anchors experienced in these waters ”

“ We have many reasons to confirm the belief that a submarine cable, manufactured and laid with strict attention to all known principles, may be regarded as a substantial property, likely to last for any length of time; for there is no evidence whatever upon record which shows any decay of the insulating medium or copper conductor of a well-manufactured cable, i. e., there is no decay inherent in the nature of a cable; all deterioration is external ”

“ Reports have been published that German submarines have been fitted up with a wire and cable cutting appliance which would make it possible for them to break through nets at will, supposing, of course, that they had been caught by the nets in such a way that no vital parts of the underwater craft had been seriously damaged. A sketch of this wire cutting device was made by the captain of a merchantman, who, while in a small boat after his ship had been torpedoed, had come close enough to the attacking submarine to make the necessary observations. ”