It is now nearly, three years since it was our agreeable task to lay before our readers a description of the laying of the Atlantic Cable of 1866, and the recovery and completion of the lost cable of 1865. Since that time a great many telegraph cables have been laid; but none have been of so much importance, or possessed so many features of interest, as that just successfully completed between France and the United States. In the first place, it is interesting as being longer by about fifteen hundred miles, and laid in deeper water by five hundred fathoms, than any direct submarine line yet in existence ; then its track Iks through a part of the Atlantis which until very recently haa been unexplored, and the nature of the bottom comparatively unknown; ;and thirdly, we look upon it with interest, because it shows that the importance of submarine telegraphic communication is commending , itself to other countries besides our own. Hitherto, nearly all the more important submarine lines have been the direct offspring, and have remained in possession of English companies; but the present cable, although manufactured and laid by an English firm, is the result entirely of French enterprise, and to a large extent owes its existence to French capital. The vital part of the longer section of the cable—or tech- nicaUy the “core “—is a copper conductor of seven wires twisted together, insulated by four concentric coatings of gutta-percha, separated from each other by an equal number of coatings, ot the material known as “Chatterton's compound “—exactly after the pattern of the cores in the last Atlantic cables—the only difference between them being in the weight of the conductor, which in the present case is four hundred pounds per mile, instead of three hundred pounds. This increase is to compensate for the additional length of the cable. Experiments have shown that the speed of signaling through submarine cables varies inversely according to their length, and directly as the weight of the conductor; so that, by adding to the weight in due proportion to the increased length, the speed obtained is the same as through a shorter cable. The core is surrounded with a serving of yarn, called the “ wet serving,” allowing of the ready access of the water to the core. Until comparatively recently, this serving was saturated with tar, but experience showed that, should a slight defect occur in the gutta-percha, the tar from the serving being in itself an insulator would sufficiently stop it up to prevent its being discovered by the electrical tests, until perhaps it was too late to remedy it. The present wet serving, however, containing no insulating fluid, permits of the instant detection of a fault. Around the serving are twisted spirally ten homogeneous iron wires galvanized, each of them embedded in five strands of Manila hemp. The cable thus completed is of a diameter of about one and a quarter inches, weighing about thirty-six hundredweight to the nautical mile, and capable of bearing a strain of seven tuns. The core of the shorter section—St Pierre to Boston— is of the same description as that of the Brest to St Pierre section; but owing to its much shorter length, the weights of the copper conductor and insulator are only one hundred and seven pounds and one hundred and fifty pounds per mile respectively. This core is also covered with a wet serving, and then surrounded with about a dozen iron wires galvanized—the outside covering consisting of a silicated material, known as “Clark's compound;” the whole forming a cable of about one inch in diameter, weighing about two and three quarter tuns to the mile. The Brest to St Pierre section was manufactured at the Telegraph Construction Company's Works at Greenwich, and transmitted piece by piece in old hulks to the Great .Eastern steamship, lying off Sheerness. This section is of three kinds, namely: 1. The heavy shore-ends for protection against ships' anchors, tides, etc., weighing 360 hundredweight per mile. 2. The “ intermediate,” of a size between the shore-end and the deep-sea portion, 127 hundredweight per mile. 3. The deep-sea portion already described. The whole of the above, 2788 knots in length, with the exception of 15t miles of shore-end, and twenty miles of intermediate, was taken to the Great Eastern. We calculate that if the various component parts of it were laid end to end, they would make a chain of over 192,000 miles in extent, or nearly eight times the circumference of the globe. The whole of the work, including the manufacture ofihe two sections, and the fitting out of the Great Eastern, occupied little more than eight months. For the accommodation of the cable on board the Great Eastern, three gigantic tanks were constructed, situated in the center, stern, and fore part of the ship, and known as the main, after, and fore tanks, respectively. Their diameters were as follows : Fore, 51 feet 6 inches diameter, by 20 feet 6 inches deep; main, 75 feet diameter, by 16 feet 6 inches deep; after, 58 feet diameter, by 20 feet 6 inches deep; with a total capacity of 169,760 cubic feet—being 27,750 feet greater than the capacity of the tanks in 1866. These immense structures were fixed to the sides of the ship, and supported by about 30,000 cubic feet of timber. The weight contained in them was about 5520 tuns, distributed as follows : Fore, 1270 tuns; main, 2580 tuns ; aft, 1670 tuns; total, 5520 tuns. The cable paying-out apparatus, consisting of an elaborate series of break-wheels and stoppers, with the measuring-machine, and the “ dynamometer,” a machine for constant.lv recorrU ing the strain on the cable, contained all the improvements that science and experience have suggested. The dynamometer especially claims our notice, as being, to our mind, 0i1.<) of the most ingenious and useful contrivances connected with the apparatus. It is placed between 'the stern of the ship and the paying-out breaks, and consists of a vertical frame-work of iron, in the center of which is fitted a grooved wheel, for the cable to pass under as it runs out over the stern of the ship. The wheel is made to sli.lo up and down the frame as the strain on the cable varies, OJ , in other words, as the cable becomes tighter between the sLin and the breaks. At the side of the machine is a scale, with the calculated strams in hundredweights marked upon it ; and a hand fixed to the sliding-wheel traverses this scale, and indicates at any moment the strain on the cable. From the indicated strain, of course, the depth of water may be judged, and the breaks arranged accordingly; but the dynamometer is of most service in cases of hauling back the cable. The ship was also fitted with a powerful set , of picking-up machines and tackle, together with buoys, buoy-ropes, mushroom anchors, and everything requisite for picking up the cable in case of a breakage, as in 1865. We must not forget to mention that the ship was also fitted with a complete set of “Wier's Pneumatic Signals,” such as we believe are in use on several of the Cunard steamers. The uses to which this excellent apparatus is put are as numerous as they are effectual. The apparatus is rather complicated in its details, but simple enough in the principle on which it works. By pressing down a lever on a series of chambers of compressed air, the air from the latter is forced along a very small leaden pipe, producing instantaneously at the distant end some mechanical effect-either ringing a bell, or moving a hand, or lifting up a small flap, under which is written the signal meant to be observed. On the Great Eastern there were—1. An apparatus at both ends of the ship for communicating various messages to both screw and paddle engines; 2. An apparatus at each of the three cable tanks for signaling to screw and paddle to stop and reverse, in case of a hitch or foul-flake in the tank; 3. An apparatus connected, by means of cams, with the shafts of the screw and paddle engines, registering the revolutions of the same on a clock placed in the engineer's office ; and 4. A communication was placed between the bows and the steering-wheel, to be used in case picking up should become necessary. Connected with some of the apparatus was also a tell-tale, which by an automatic action would indicate whether the order sent had been obeyed or not. We have given so lengthy a description of this pneumatic 274 Jdtitifit %mtmm. [OCTOBER 30, 1869. apparatus, because we believe it to be one of the most useful inventions in the signaling department yet made. If pro-1 perly fixed, it is almost impossible for it to get out of order. With reference to the ship itself: so much has been said about the Great Eastern, that we do not wish to trespass upon our readers' patience with any long discourse upon the subject; but still the ship remains one of the wonders of the world, and we cannot pass on without some slight reference to its astonishing size and capabilities. The increased size of the cable tanks has taken away considerably from the convenience and appearance of the cabin and saloon accommodation, but still the cabins more resemble rooms in a hotel than what we usually understand by ships' berths ; and the saloons,especially the grand saloon, are still far beyond our ideas as to the size of any rooms to be found on board a ship. In fact, the ship more resembles a floating town than anything else we can think of. On what other ship can one find full-sized premises for butchers, bakers, plumbers, carpenters, blacksmiths, and fitters, with saw-mills, roperies, farm-yards, sheep-pens, pig sties, and store-rooms big enough to contain stores for a small army ? It cannot be doubted that for anything else besides cable-laying, the Great Eastern is too big. The expenses of keeping her in trim, and her daily expenses while at sea, are such that no ordinary number of passengers would, at the usual fares, make hcr pay. Sat for cable-laying, she is the ship par excellence; and we doubt very much whether either of the present Atlantic cables would have been laid 1)ut for her size and general adapt ability to the purpose. In the first place, no other ship could have taken the entire cable on board, thus obviating all t he risks attcndant upon changing from one ship to another in mid-ocean, as was done with so much danger with the first cable, in 1858. In the second pl ace, her behavior at sea fits her better than any other ship in existence for cable-laying. She rolls to perfection when she has a heavy “ swell” to encounter, but all her movements are of so regular and easy a character, that, in even heavy gales, the operation of cable-laying can proceed without any interruption whatever.
This article was originally published with the title "The French Atlantic Telegraph"