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 lies through a part of the Atlantic which until very recently had 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 technically 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 of 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 illustration shows the three weights
of cable used. All had an identical core of 7 copper strands. On
the left is the shore-end cable, heavily armoured to resist damage
from rocks and ships’ anchors. On the right is the intermediate
cable, used to run from the shallows near shore out to deeper water.
In the center is the deep-sea cable, the main length of the run,
and having the lightest armouring. The diagrams are to scale; the
deep-sea cable is about 1” diameter. |
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 15½ 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 of the two sections, and the fitting out of the Great Eastern, occupied little more than eight months.
The Departure From Sheerness, June 13, 1869
|
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 tune; 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 constantly recording 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, one 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 slide up and down the frame as the strain on the cable varies, or, in other words, as the cable becomes tighter between the stern and the breaks. At the side of the machine is a scale, with the calculated strains 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 apparatus, because we believe it to be one of the moat useful inventions in the signaling department yet made. If properly 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 her pay. But 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 but for her size and general adaptability to the purpose. In the first place, no other ship could have taken the entire cable on board, thus obviating all the risks attendant 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 place, 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.
When the Great Eastern left Portland for Brest, after taking in her supply of coal, she had on board about four hundred and fifty persons, including the members of the electrical and engineering staffs, the cable hands, and the crew; and one would think, looking at the list of stores that the whole of London had been ransacked for the sustentation and inner edification of this miniature army during the voyage to Newfoundland and back. Leaving out a thousand items of but little consequence, we need only refer to the 100,000 pounds of meat and poultry, 30 tuns of vegetables, 35 tuns of bread and flour, 15,000 eggs, and over 2,000 dozen of liquors of various kinds, to give our readers some idea of the provision necessary to be made for a six weeks’ trip.
We have made a rough calculation of the cargo of the ship, including her engines and boilers, when she left Portland, and believe the following to be a very near approximation—it is certainly not over the mark: Cable, 5,520 tuns; cable-tanks and water, 400 tuns; timber shorings for tanks, 500 tuns; paying-out and picking-up machinery, 120 tuns; ship’s stores, 250 tuns; coals, 6,400 tuns; engines and boilers, 3,500 tuns; total, 10,690 tuns. Her draft at starting was about 34 feet aft, and 28 feet forward. This, of course, decreased as the cable was paid out, until, at the end of the voyage, it was only about 25 feet aft, and 23 forward.
Before proceeding with a narrative of the laying of the cable, we wish to describe the arrangements made for the electrical testing of it during submersion. These were, with one or two slight exceptions, identically the same as in 1866. Their most interesting feature is the keeping up of a constant test on ship and shore for insulation, by a plan devised by Mr Willoughby Smith in 1865, at the same time allowing of tests for the continuity of the conductor, and free communication between ship and shore to be kept up without in any way interfering with the insulation test. By this means, should a “fault” pass overboard into the sea, it is detected at once, and the paying-out may he stopped before any considerable length of the cable has been allowed to run nut. The advantage of this system over the old is apparent from the fact, that formerly it was possible for three or four miles of cable to run out between the occurrence of the fault and its detection; whereas now, except under very peculiar circumstances, within two or three minutes after a “fault” passes overboard, it can be detected, and the signal given to stop the ship.
In conclusion, nothing that could in the least possible way facilitate the execution of the great work was left undone. All the arrangements were of the most complete character, and were placed in charge of men who are unrivaled for their practical knowledge of submarine telegraphy.
The expedition started from Brest on Monday, the 21st of June, and the American end of the cable was safely landed at Duxbury, near Boston, on Friday, the 23d July. The five weeks which elapsed between those two dates were enlivened with incidents of the most interesting nature, and it is to these we shall now refer.
For the first three days all went well. The weather was very fine; the paying out of the cable proceeded without a hitch, and all were beginning to indulge hopes that, as in 1868, the voyage would be made without the occurrence of those unfortunate “faults” which cause such delay and trouble. But our hopes were soon upset, for on the fourth day, the 24th June, shortly after daybreak, we were struck with consternation by the intelligence that there existed an electrical fault in the cable. The intelligence was conveyed all over the ship by means of a powerful gong, which was planted outside the electrical room, ready to be hammered upon as soon as anything of a suspicious nature was indicated on the testing instruments. In obedience to the gong, the ship was speedily stopped, and the engines reversed, The tests showed the fault to exist very near the ship; so, without any more ado, the picking-up engines were set to work, and hauling back commenced. At every three hundred or four hundred yards of cable hauled back, a fresh test was made, until, in about a couple of hours, it was found that the faulty place had come on board. Other two hours were sufficient to make a fresh splice between the cable paid out and that remaining on the ship, and then operations were resumed as if nothing had happened. Fortunately, the weather was very fine and the sea calm, and the hauling back was .in consequence attended with but little danger. The occurrence of the fault was perhaps advantageous, inasmuch as it served more fully to impress the staff with the importance of having everything in c mplete readiness for an accident.
The fault was afterwards found to consist of a minute hole penetrating the coatings of gutta-percha; whether caused accidentally or purposely it is impossible to say. It may be asked why it could not have been discovered before it left the tank. The answer probably is, that it was of too minute a nature to indicate its existence on the testing instruments, until, by passing through the paying out machines, and then undergoing the pressure of the sea, it became more fully developed.
To give our readers some idea as to how a fault is detected, we may (for this purpose only) compare the cable to a long pipe, sealed up at one end into which water is being forced. As long as the pipe remains perfect, only a certain amount of water can be put into it, according to its capacity, and once filled, there is no flow of water; but if, when the pipe is full, a small hole be made in it, the water will of course rush out at once, indicating the existence of the hole by causing a fresh flow of water into the pipe. Now, the cable is always kept charged with electricity up to its full capacity—or, in other words, till it can take no more—and as long as it remains perfect, there is practically no current flowing from the battery into it; but immediately on the development of a fault, or communication between the conductor of the cable and the earth, a portion of the charge escaping through the fault causes a fresh supply of electricity to flow from the battery. By having a delicate instrument fixed between the battery and the cable, this increased flow is at once made apparent.
Another similar fault occurred on the 26th, fortunately unattended with any more serious consequences than in the first case.
On the 29th June, the weather, which had up to that time been so fine, suddenly changed,
A strong breeze sprung up towards evening, which, by the morning of the 30th, had increased to a heavy gale. The sea was very rough indeed; and the frequent violent lurches of the ship began to cause some apprehensions as to the safety of the cable. Everybody devoutly hoped that we might get through the gale without having to stop and haul back on account of a fault; but our hopes were frustrated, for just in the very hight of the gale, the dismal notes of the gong announced that another fault had indicated its existence on the testing instruments. The engines were reversed, and hauling back commenced, amid the greatest excitement. At every lurch of the ship, the strain indicated on the dynamometer rose to an alarming extent, and as the hauling in proceeded, it seemed continually as if nothing could prevent the breakage of the cable. Still the testing showed the fault to be outside the ship, and still the strain on the cable kept increasing, until at last, in one tremendous lurch of the ship, a whiz was heard, sending a thrill of horror into the bosom of every one on deck. The cable had parted; but by the greatest good fortune the rupture occurred inside the ship, and by a most admirable promptness, the breaks were successfully put on before the broken end could run out over the stern.
The gale was still far too heavy to risk hauling in any longer, so, with not a moment’s delay, the end of the cable was secured to a huge buoy, and sent adrift, to be picked up again as soon as the weather became more moderate. The remainder of that day and the whole of the next were spent in steaming about in the vicinity of the buoy, keeping as near to it as possible—the great ship continually rolling in a most ungainly fashion.
At the Stern of the “Great Eastern”
Shipping a Heavy Sea
About to Cut and Buoy the Cable |
On Friday, the 2d of July, the weather was sufficiently fine to enable us to pick up the buoy to which the cable was attached, and a very few hours sufficed to get the end of the cable on board. After hauling in about a quarter of a mile of cable, the faulty place, which had been the original cause of the stoppage, was brought on board, and very speedily the ship resumed her course.
These three faults well illustrated the advantages of the system of testing employed; for in each case, the existence or the fault must have manifested itself within three minutes after it left the ship—in fact, as soon as the pressure of the sea could force the water into the flaw. After stopping the engines, of course the “way” of the ship would carry her seven or eight hundred yards before the paying out could come to a dead stop, and this, added to perhaps a quarter of a mile run out previous to the detection of the fault, would account for the three fourths of a mile, more or less, which in each case had to be hauled in before the fault was secured. Practically, however, we may say that each of the faults was discovered immediately on its leaving the ship—and this is the great advantage of Smith’s system. Neither of the faults was bad enough to prevent the most perfect communication taking place between ship and shore while the tests for localizing the fault were being made, so that the ship could give any instructions whatsoever to the shore which were considered necessary.
On the 5th July, we experienced another heavy gale; but as the testing of the cable remained perfect, the paying out was not interrupted at all. In fact, after the 2d July, nothing occurred to interfere with the progress of the work. The St. Pierre shore end had been laid in readiness for our arrival by the William Cory, and the work of the Great Eastern was completed on the 13th July.
The rate of paying out the cable was from five and a half to six knots per hour, the ship running five to five and a half knots. Very likely this speed might have been increased without incurring danger; but, considering the immense size and weight of the ship, and the difficulty of stopping her in case of accident, it was no doubt best to keep the speed within narrow limits.
As to the track of the cable, it seems from the soundings taken that the bottom is composed, the greater part of the distance, of the fine mud usually called “ooze” consisting of very minute shells—so minute that without a microscope the shape is not discernible. This “ooze” constitutes the very best bed for a submarine cable. In fact, judging from the experience of 1866, the cable lies in it as securely and free from harm as when coiled in the tanks at the manufactory; and if picking up should become necessary, the softness of the “ooze” renders the grappling of the cable comparatively easy.
The position of the present cable has one advantage over that of the English cables—namely, that it has been kept carefully off the Newfoundland Banks, and will therefore not be liable to the breakage by icebergs which have already caused such expense and trouble to the English company. The cable is conducted several miles to the south of the “Great Newfoundland Bank,” and then proceeds in a northwesterly direction to the western side of St. Pierre Island, passing along a deep gully between the “Green Bank” and the “St. Pierre Bank.” The length of the course selected is about 2,330 knots, and the amount of cable paid out 2,580 knots--making about ten per cent allowance for “slack,” or spare cable paid out to cover the inequalities of the bottom, and to allow of picking up, should such become necessary Without taking notice of the 300 knots from the Brest shore, and the 500 knots from Newfoundland, where the water is shallow, the depth varies from 1,700 to 2,700 fathoms. the deepest part being situated in about 45° north, and longitude 43° west.
Two days after the completion of the Brest and St. Pierre section, the laying of the section from St. Pierre to Boston was commenced. The cable was divided into three pieces, coiled respectively in the William Cory, the Scanderia, and the Chiltern.
The course of this cable runs through shallow water nearly the whole distance, and therefore the paying out of it was not attended with that excitement which existed during the voyage from Brest to Newfoundland. It was felt that if even the cable should break, and be for a time lost, it would be a perfectly easy matter to grapple for it and pick it; so that when, on the 20th July—through a “foul-flake” or tangle in the tank of the Scanderia-the cable did actually snap, a very few hours sufficed to drop the grappling-iron, haul up the cable, make a fresh splice, and resume operations in the usual way. The foul-flake was about the only thing that caused any considerable delay in the paying out of the cable, which was completed on Friday, the 23d July, in the presence of a large number of spectators, including about a hundred representatives of the American press, who came down en masse, each of them struggling to obtain the earliest information.
The landing place of the cable was at Duxbury, a few miles from Plymouth, celebrated as the spot whereon the Pilgrim Fathers first landed—a coincidence which the Americans did not fail to make the most of in the speechifying which followed the completion of the work.
1885 map of Duxbury showing the cable
station
and the cable laid across the marsh |
The length of this shorter section of the cable was 750 knots; adding which to the 2,580 knots from Brost to St Pierre, we have continuous submarine communication for 3,330 knots. The signals through the whole of this immense length are as distinct and readable as between any two points on an English land line, and can be sent at a much greater speed than the business of the line is likely to require. The signals at present consist of the oscillations of a spot of light on a screen, reflected from the mirror of a “Thomson’s Reflecting Galvanometer,” as in the English cables; but we believe this is likely to be superseded by a very delicate printing instrument, also, if we are rightly informed, the invention of Sir W. Thomson.
Thus is completed the first direct line of submarine communication between Europe and the United States. No doubt there will be found plenty of room for it, without injuring, in any material degree, the interests of the English companies. We notice that the latter have already reduced their tariff, in order to keep up with the French company. This, of course, will be a great boon to a large section of the commercial fraternity, to whom the high tariff hitherto existing has been an insuperable barrier to frequent communication with America.
But, setting aside the interests of private companies, which are of comparatively little consequence, we believe that the present cable will serve still more strongly to unite in sympathy the Old World to the New, and to make it more apparent that the interests of the two worlds are bound up together. We would fain hope that by the increase of traffic, induced by a decreased tariff, there will be found room for still another cable across the Atlantic.
We confess to a slight feeling of pride that this great work has been accomplished by Englishmen; but waiving this, we rejoice that the three greatest nations of the world—England, France, and the United States—have joined in the execution of a work which cannot fail to help forward in a high degree the progress of civilization.
