In the present paper I do not propose to enter into any considerable account of the history of the Atlantic Telegraph, which is well known, but rather to confine myself to the means employed to carry out the project.
The idea of an Atlantic Telegraph may be said to date from the time that the first telegraph cable was laid across the English Channel. No sooner had the submarine telegraph been completed from Dover to Calais, than it was said—"If we can cross this channel of the sea, cannot we equally conquer the broad Atlantic?" The larger the space to be overcome, the greater was the relative value of the achievement. From England to France but a few hours were saved; while between America and England electricity would accelerate communication by many days.
That this idea was brought to a practical result is due, in a great measure, to the indomitable energy of Mr. Cyrus Field.
When the question of the Atlantic Cable was practically gone into, it took some years to mature the plans, because a great variety of points had to be discussed and dealt with. The first that arose was the possibility of passing the electric current through an insulated wire to so great a distance as two thousand miles without a break, as comparatively but short distances had been previously dealt with in telegraphing; and if signals could be transmitted, whether they could he passed sufficiently quickly in succession to prove remunerative in forwarding messages. Doubts on this point were removed by a series of experiments instituted by Sir Charles Bright, in conjunction with Mr. Whitehouse, upon the long lengths of underground gutta-percha covered wires belonging to the British and Irish Magnetic Telegraph Company, which were so connected on various occasions as to afford a length of upwards of two thousand miles in one continuous circuit. Signals were clearly and satisfactorily transmitted through this vast distance at the rate of two hundred and ten, two hundred and forty-one, and two hundred and seventy per minute. The retardation of the electric current that was found to arise from induction was overcome by using a succession of opposite currents. By this means the latter or retarded portion of each current was blotted out, as it were, by the opposite current immediately following; and thus a series of electric waves could be made to traverse the wire one after the other—several being in the act of passing onward at different points along the conductor at the same time.
It was also necessary to determine the nature of the bottom of the Atlantic, whether it was suitable for electric cables, or whether it was too deep or rugged to be dealt with. Repeated series of soundings proved that the bottom of the Atlantic was a safe bed, consisting of a gently undulating plateau nearly the whole of the distance between Ireland and Newfoundland, at a depth varying gradually from one thousand seven hundred to two thousand three hundred fathoms. These depths, although very great, were insignificant when compared with those further south than the belt of the ocean between these two points. The bottom itself was found to consist principally of a soft sandy deposit—partly formed by the shells of animalculae, so small that when taken up they required a very strong magnifying glass to demonstrate that they were shells at all! These minute creatures live near the surface and their shells have been rained down, so to speak, for ages. When specimens of the soundings brought up are examined, they are found to be similar to the material forming our chalk cliffs, which have no doubt been similarly built ages ago. As these microscopic shells were so fragile that a breath would almost destroy them, they afforded a proof that there were no currents at the bottom moving over the surface of this plateau; for had the shells been rolled to and fro, their delicate organism would have been destroyed.
An idea very generally prevailed that the ocean was practically unfathomable; that is to say, that, owing to the pressure of water, nothing could possibly sink to the bottom, and that sooner or later everything—even a cannon-ball— would find itself in a state of equilibrium and descend no further. Science had, however, shown that owing to the water itself being less compressible than even metals, its specific gravity would not be increased at great depths by the pressure of the column of water above, to so great an extent as the weight used for sounding, of whatever material it was composed. It therefore followed that at any given depth the sounding lead would be relatively heavier as compared with the water around it, than when at the surface; and hence the lower it went the greater would be its tendency to sink.
The sounding apparatus used was of a very ingenious kind, and its arrangement will be best understood by a reference to fig. 1.
A rod of iron (B) is attached to the sounding-line, at the bottom of which are fixed a few quills with their ends open. This rod is passed through a hole in the centre of a cannonball (A), which can move loosely upon the rod, but is held in its position by a cord passed round it and fastened at each end by loops to two curved arms attached to the sounding-line. On the line reaching the bottom, the weight of the cannon-ball drives the end of the rod into the sand. The curved arms fall down and release the loops holding the cannon-ball. On the line being hauled up, the rod then passes clear, leaving the cannon-ball at the bottom, and carrying to the surface the quills containing some of the sand or ooze from below.
In constructing the first cable, in 1857, it was considered necessary that it should be capable of sustaining five or six miles of its own weight in water, when suspended vertically; so as to allow of laying to, if required, during submersion. At the same time the cable had to be heavy enough to draw itself freely from the hold, somewhat in excess of the ship's speed, and to sink readily; so as to avoid lashing of the waves in rough weather, and to pass without interference through the currents near the surface. After experiments on upwards of sixty kinds of cables, one was selected with a central conducting strand composed of seven small copper wires and coated with three distinct layers of gutta-percha. This core was then surrounded with tarred yarn, and covered over with eighteen strands of iron wire, for an outer protection, as shown in fig. 2.
The object of using a bundle of wires instead of a single solid conductor, was to prevent a flaw in one of the wires, at any point, interfering with the conductivity of the cable; as the electricity could in such case pass along the remaining wires of the strand without interference. In the same way three coatings of gutta percha were applied successively, so that any minute air hole or other defect in one layer would be covered up by the other layers. The chance was excessively small of a defect in manufacture occurring in each of the three layers at precisely the same point! It is well known that this cable when laid in 1858 was worked for a month, and then communication ceased; owing to the gutta percha insulation becoming defective at a fault, which the tests shewed to be about two hundred and seventy miles from Valentia. The electrical leakage through the fault had been augmented by the strong currents used in passing signals.
This failure discouraged further prosecution of the enterprise for some years; but the experience gained by it was of the greatest importance, and really formed the germ of the more permanent success achieved this year. It was seen that with deep sea cables it was advisable to construct them proportionately stronger and specifically lighter than the first Atlantic line, so that they might be recoverable at great depths. It was also obvious that for so long an unbroken circuit the conductor should be larger and the gutta percha insulation more perfect, so as to enable a greater speed of transmission to be attained with a less intense current; in fact, the weaker the electric charge capable of producing an effect at the other end, the less tendency it would have to burst its way through the gutta percha at any defective point, and, therefore, the more likely the cable would be to last.
In 1865 a new Atlantic cable was made, which was a great improvement in many respects upon its predecessor. The outer protecting strands were formed of a combination of iron wires cased with hemp, saturated with a tarry compound as a protection from rust. The copper conducting wire consisted of seven strands as before; but weighed three hundred pounds per mile, or nearly three times that of the 1858 conductor. It was insulated by no less than eight coatings of gutta percha and a viscous insulating compound laid alternately over one another. The wire had thus not only three times the conducting power, but a far better insulation than its predecessor; and was capable of passing seventeen words per minute, while the former cable could only transmit three or four words per minute. The cable as a whole was specifically lighter in water and far stronger. It weighed only fourteen hundredweight in water, while the old cable weighed thirteen hundredweight; but it could withstand the strain of seven tons and a half, while the strength of the 1858 cable was only about half as great. The difference will be better understood by a reference to fig. 3.
As the risk to submarine cables when laid is in a great measure confined to the shallow water near each shore, where there is the chance of damage from anchors, fishing trawls &c, the shore ends of the Atlantic Cable, for a distance of thirty miles out, were made of an exceedingly massive form. Their weight is no less than twenty tons per mile, and they are protected by an outer spiral casing of iron rods; so that, even if accidentally caught by the anchor of a line-of-battle ship, they would probably hold it without suffering injury.
The weight and bulk of the cable being so enormous, when multiplied by the length to be made (twenty-three hundred miles) it was determined to engage the Great Eastern, which was then seeking employment almost in vain. By this arrangement the whole of the cable could be stowed in one ship, while without her aid four ships of the largest size would have scarcely sufficed; and, as in 1858, the cable would have had to be much smaller in size. Even with present experience it would be a most dangerous experiment to attempt to lay a cable piecemeal across the Atlantic from a series of vessels; for rough weather might at any time prevent the ends being successively joined, as each ship finished its portion of the task.
The mission of this vast ship was at last discovered, and she was speedily prepared for the work. Huge tanks were built within her to receive the cable, and keep it continually saturated with water; so that in case the slightest fault occurred prior to the insulated cord passing into the sea, it would be at once detected.
I now come to the machinery devised by Messrs. Canning and Clifford for laying the cables of 1865-6.
The object of the paying out machinery is simply to check the speed at which the cable would otherwise run out of the hold, so as to regulate its delivery into the sea at a rate slightly exceeding that of the vessel itself. Without such a restraint, four or five thousand miles of cable might be paid out in traversing the eighteen hundred and eighty-six miles between Ireland and Newfoundland; but by aid of the gentle check put on, only from ten to fifteen per cent. of slack was actually used. Apart from the cost of any excessive length used, there would also have arisen the difficulty of stowing it away, and the electrical objection to any increase in length of a telegraphic circuit already so great.
The paying out apparatus will be best explained by a reference to the diagram fig. 4.
The cable on coming up from the tank in the hold, passes along a conducting trough to the first of six leading V wheels of the machine. It does not take a turn round this wheel, but merely passes over the top of it and the five other wheels consecutively, being pressed down into their grooved rims by small weighted wheels or jockey pulleys, around the circumference of which there is a band of indiarubber so as to produce a retarding effect upon the cable when necessary. Each jockey pulley turns upon an axle at the end of an arm centered at (A), and the weights on the jockey pulleys can be released at once by turning a hand-wheel (B). After leaving the last of these wheels, the cable takes several turns round a large drum (6'), the axle of which is connected to a break arrangement; by means of which the speed of the drum with a given strain is checked or accelerated, according to the increase or reduction of a series of hand-weights that can be attached or taken off as required.
Between the stern of the vessel and the machine the cable was bent somewhat out of the straight line by being led under the grooved wheel of a dynamometer D. This wheel had a weight attached to it, and could be moved up or down in an iron frame. If the strain upon the cable was small, the wheel would bend the cable downwards, and its index would show a low degree of pressure; but whenever the strain increased, the cable in straightening itself would at once lift the dynamometer wheel with the indicator attached to it, which showed the pressure in hundredweights and tons. The principle is similar to the ordinary spring letter weighing machine. The amount of strain, with a given weight upon the wheel, was determined by experiments; and a hand-wheel in connection with the levers of the paying-out machine was placed immediately opposite the dynamometer, so that directly the indicator showed strain increasing, the person in charge could at once, by turning the hand-wheel, lift up the weights that tightened the friction straps, and so let the cable run freely through the paying-out machine. Although, therefore, the strain could be reduced in a moment, it could not be increased by the man at the wheel.
Provision was also made for picking up the cable in case of accident. As ships will not steer stern foremost, in operations of this nature the head of the ship has to be kept to the cable as it comes up from the sea. An auxiliary steam engine was fitted up in the bows of the Great Eastern, geared to a pair of picking-up drums, round which several turns of the grapnel rope would be laid. Another dynamometer (or pressure measurer) was placed between these drums and the bow sheave, to indicate the strain upon the grapnel rope; and thus show when the cable was hooked, or when the pressure was becoming so great during the hauling-in process as to imperil either the grapnel or the cable.
The Great Eastern was commanded by Captain Anderson, and the arrangements for laying the cable were under the control of Messrs. Canning and Clifford.
During the laying of the cable in 1865, several faults were successfully discovered after they had passed overboard. In the two first cases the cable was drawn back, and the faults were found to have arisen from a small piece of the iron wire covering the cable having by some means been driven through the gutta percha, so as to touch the conducting wire, and thus producing complete electrical leakage. On the third occasion, when drawing back the cable, the drifting of the Great Eastern brought the cable across one of the projecting hawse pipes at her bow; and before the injured part could be secured on board, it broke. They were then in soundings of about two thousand fathoms, at a distance of ten hundred and fifty miles from Ireland. After making repeated efforts to recover the lost cable with grapnels, they had to return to England unsuccessful, as the grappling ropes were not strong enough to raise it to the surface.
Further capital was at once raised, and another cable made similar to that of 1865 in all respects, except as regards the tarry composition coating the outside hempen strands, which was found to interfere with the speedy detection of faults, by preventing ready penetration of the water in case of injury. The tests for faults during the expedition of 1865 were periodical, intervals being allowed between each for passing messages between ship and shore; but by an ingenious modification it was arranged that the connections of the cable of 1866 should be so made as to keep it under a continuous test for insulation, and yet allow communications to continue between those engaged at each end of the cable. This mode of testing is shewn in diagram fig. 5.
Suppose the leakage through the resistance R, connected with the shore end of the cable, to equal that through the gutta percha of four miles of the cable, this amount of leakage would flow through the galvanometers G on shore and G on board ship to earth, and thus a constant deflection would be observed, so long as the cable was kept charged at a uniform tension. But should the tension be altered, either by the occurrence of a fault in the cable, or when signalling by reversing the current on board ship or pressing down the key (K) in connection with a smaller resistance r on shore, a change in the deflection of both galvanometers then becomes at once observable. By this means constant communication can be maintained with shore, and any injury to the cable at once detected.
The expedition of 1866 was favoured by fine weather, and everything went smoothly till the 18th July, when the cable became entangled in the hold, through one flake fouling another. The paying-out part of the coil caught three turns of the cable immediately under it, and drew the bights into the eye of the coil in a confused tangle. The Great Eastern was fortunately brought up in time to prevent the huge knot of cable entering the machinery; and in the course of a few hours the confused mass was unravelled by Messrs. Canning and Clifford, and the work proceeded.
No further interruption occurred, and the American end of the cable was successfully landed at Heart's Content Bay, Newfoundland, on the 27th July, in perfect order.
The search was now to commence for the lost end of the cable of 1865, lying at the bottom of the ocean, at a depth of two miles from the surface.
The difficulty of the undertaking may be readily conceived when we consider that a submarine cable when laid forms nearly a straight line upon the bottom; but in raising a bight of it to the surface, a considerable length beyond that upon the bottom is required to form the two curved sides, subtending the angle brought up. This will be more clearly seen from the following diagram fig. 6, where K shows the line of a cable on the bottom of the sea forming the base of the triangle, and L L' or M M' the two sides to be formed in bringing the cable upward.
In laying the cables, ten to fifteen per cent, of slack had been paid out, and this surplusage would of course assist in forming the two sides of the bight. In such depths as the Atlantic, this excess would not, however, be sufficient; and it was therefore arranged to lift the cable partially at several points near to one another at the same time, by the co-operation of the three ships. If this could be accomplished, and the outermost vessel then broke the cable by putting on an additional strain, a length would be left free to form the outer side of the bight, and the cable would come up readily.
Let us now look at the arrangement of tackle which was destined to recover from ocean depths of more than two miles the value of half-a-million sterling.
The line devised for this wonderful bottom fishing consisted of a combination of steel wire and hemp strands spun together. The grappling rope complete measured two inches and a half in diameter and was built up of seven smaller ropes (six laid round one), each composed of seven wires served with tarred hemp. The rope complete, therefore, consisted of no less than forty-nine wires, each insulated from its neighbour by the yarn covering it. The aggregate strength of this bundle of steel fibres was sufficient to bear a strain amounting to thirty tons. The hemp reduced greatly the specific gravity of this huge rope in water, while giving increased strength and elasticity; so that, though weighing about eight tons per mile in air, it was but three tons when submerged; and thus only put a strain of about eight tons upon the picking up machine when two and a half miles, with the grapnel attached, were hanging down in the ocean.
For fish-hooks a number of five-pronged grapnels, of the shape shown in fig. 6, were on board, weighing from two and a half to four hundred-weight each. Projecting springs were so attached to the grapnel shank as to prevent the cable leaping up when once secured in the tenacious grasp of the flukes. The picking up machine consisted of a pair of large drums at the bow of the vessel as already described, geared to a powerful "donkey" engine by which they could be made to revolve in either direction as required, like the winch of a fishing rod. To complete the similitude:—Between these drums and the how sheave the grappling rope passed under the wheel of a dynamometer, the duty of which was precisely analogous to that of a fishing-float—to give warning of any "nibble." A "bite" in this case was indicated by a tug on the line to the extent of an additional three tons when the bight of the cable had been hooked! The strain then ran up from the seven and a half or eight tons due to the pendant grappling rope, to ten and a half or eleven tons when the prize was caught. My readers can fancy the excitement on board, upon a nibble being shown by a "bob" of the dynamometer index!
The observations taken, principally by Captain Moriarty, R.N., last year formed the sole clue as to the point in mid-ocean where the cable slumbered. The skill of Captain Moriarty soon set the first doubt at rest, by unerringly guiding the expedition to the spot where it had been lost. The Albany, grappling ship, with H.M.S. Terrible, made their way first to the rendezvous, in longitude 38° 50' W., and commenced the search for the tiny rope in a depth of fourteen thousand feet of water, or nearly the height of the peak of Mont Blanc. The Albany soon hooked the cable, and on the 10th August lifted it some distance and attached a buoy. In the night, however, while a heavy sea was running, the buoy chain parted and the cable went to the bottom again.
This was the commencement of a most exciting hunt. On the 12th the Great Eastern and Medway arrived; the great ship drew the rope more than half a mile on the 15th, but in the act of buoying, the rope slipped. Two days after she again got hold of the cable, and this time raised the bight above the surface to the bow sheave. A hearty cheer greeted its appearance, but had scarcely died away when the cable was once more lost;—the weather being too rough for the boats to co-operate in securing it, the cable parted before it could be brought on board, The different ships of the squadron repeatedly grappled it, but through boisterous weather they failed to secure the prize. In one instance, when the cable broke away, a man was caught by the grapnel rope flying back, and hurled many feet from the forecastle framing down to the deck below.
As the cable at the bottom, where they had been so long working in the neighbourhood of longitude 38° 40' W., was by this time greatly fouled and encumbered with various grapnels and ropes which had given way in the many efforts to raise it; and as the depth of water was somewhat less at the point where the previous day's observations had been taken by Captain Moriarty (during the expedition of 1865), it was resolved to proceed to that point and try again. The exact spot was again indicated by his great nautical skill; and on the 1st September operations were re-commenced at longitude 36° 7' W., in about eleven thousand feet of water and, fortunately, in calm weather. The cable was soon caught by the Great Eastern, lifted one and a quarter mile from the bottom and buoyed. She then shifted ground a few miles to the westward, and at night again hooked it. The Medway at the same time grappled the cable two miles further west, and was signalled by flashes of light to haul up quickly, so as to break it, and thus to take the strain off the portion the great ship had hold of. She did so; and the bight then came in readily but slowly, as if reluctant to leave the soft ocean bed upon which it had been so long reposing. With a strain of eleven tons upon it, the tough unyielding fishing-line came over the bows as rigid as a bar of iron; and as "slow but sure" is an axiom in cable fishing, so, slowly but surely, coil after coil of the huge grappling rope was drawn on board by the picking up machine; until at last, amid breathless silence, the long-lost cable for the third time made its appearance above the water.
In a few minutes suspense was relieved by the tests showing the cable to be in good order; and immediately afterwards the answering signals arrived from the telegraph office at Valentia.
The cable when brought up was parti-coloured like a snake, half grey with the ooze of microscopic shells on which it had rested, and half black: showing that it had not thoroughly sunk into the material forming the bottom of the Atlantic, but had rested undisturbed and only half covered.
After splicing the end to the spare cable on board, the rest was laid successfully, without hitch or difficulty, to Newfoundland, on the 8th September—forming a second line of communication with America.
This cable tested on completion even better than that of 1866, owing to the gutta percha of the twelve hundred miles laid in 1865 having become gradually consolidated by the continued pressure of the enormous weight of water, and to the uniformly low temperature (about 39° Fahr.) of the bottom of the sea in those great depths.
The manner in which this final and successful attempt was carried out will be better understood by a reference to the diagram (fig. 7), in which the relative positions of the ships engaged in the operation are shown, and also the arrangements by which sufficient "slack" was gathered in to form the bight lifted to the surface.
I will now describe the telegraph instrument devised by Professor Thomson for working the Atlantic cables—the object of which is to produce a full and visible signal from an extremely minute movement of the magnetic needle.
The apparatus consists of a small and exceedingly light steel magnet, with a tiny reflector or mirror fixed to it—both together weighing but a single grain or thereabouts. This delicate magnet is suspended from its centre by a filament of silk, and surrounded by a coil of the thinnest copper wire, silk covered. When electricity passes through this surrounding coil of wire, the magnet and mirror take up a position of equilibrium between the elastic force of the silk, and the deflecting force of the current from the cable circulating through the coil. A very weak current is sufficient to produce a slight, though nearly imperceptible, movement of the suspended magnet. A fine ray of light from a shaded lamp behind a screen at a distance is directed through the open centre of the coils upon the minor, and reflected back to a graduated scale upon that side of the screen which is turned towards the coil. An exceedingly slight angle of motion of the magnet is thus made to magnify the movement of the spot of light upon the scale, and to render it so considerable as to be readily noted by the eye of the operator. The ray is brought to a focus by passing through a lens. By combinations of these movements of the speck of light (in length and duration) upon the index, an alphabet is readily formed.
The magnet is brought back to zero after each signal by the magnetic action of the earth, or else by the use of a small adjusting magnet.
The plan usually adopted for re-inforcing the effect of a current on ordinary lines of telegraph is to let the magnet deflected (or soft iron attracted) make contact with a metallic stud, and thus bring into play a local battery to produce a more marked signal. With the two thousand miles circuit of the Atlantic cable, however, it was desirable to use currents of such small power, that the signal produced would not suffice for the firm contact requisite to turn on the local battery. The introduction of the mirror system rendered this unnecessary, through multiplying and magnifying the Atlantic signal by the agency of imponderable light!
This plan was put in practice with the Atlantic cable of 1858; and the messages then transmitted were read by the receiving clerk holding down the key of a recording instrument, whenever the ray of light began to move from zero upon the scale; as soon as it commenced returning to zero the clerk released the key. Thus marks and blanks were produced upon the riband of the recording apparatus, corresponding with the movement of the light; and letters were formed by these combinations of conventional marks.
This example of the paper tape used in 1858 was not part of Bright’s article, but is included here to illustrate his description of how the messages were recorded.
Image courtesy of National Museums Scotland
The manner in which the ray of light is reflected back upon the screen from the slightly moving magnet will be better understood by a reference to the diagram, fig. 8, where A represents the position of the small mirror attached to the magnet, and B the screen at a distance upon which the ray is thrown back at an angle.
A description of the method devised by my brother and myself, many years since, for determining the exact distance of a fault in a submarine cable or telegraph wire from the testing point may, I think, prove interesting, especially as by its means the exact position of any injury or defect in the Atlantic cables, prior to or during their submersion, has been from time to time detected.
Electricity always selects the shortest and easiest route to pass by. A thin wire offers more resistance than a thick wire of the same metal, exactly in the ratio of the sectional area of one to the other. Thus a yard of very thin copper wire will offer fifty times as much resistance to the current as a yard of copper wire fifty times its sectional area and weight, therefore one yard of the thin wire will be an electrical measure of fifty yards of the thicker wire and so on.
Lengths of very fine wire, wrapped with silk or cotton (so as to insulate it and prevent the lateral escape of the current) are rolled upon a series of bobbins (like spools of cotton used for needlework.) Considerable lengths of fine wire are thus comprised in a very small bulk, representing, in their resistance to electricity, a given number of miles of the thicker cable wire. The equivalent lengths are ascertained beforehand by experiment. Suppose, then, a series of bobbins provided, which in this sense represent various lengths of cable from one mile to fifty, or more, each; and let means be provided of placing them in metallic connection in a convenient case. By such an arrangement we can have in a small box the electrical equivalent of any given length of cable.
Now let us suppose that the shore end of a faulty length of the cable be taken, and that a galvanic battery be connected with one pole to earth, and the other pole be joined to the faulty cable wire and the series of resistance coils as shewn in fig. 9.
The needle of a galvanometer, A or B, placed in each circuit will then be equally deflected, provided the resistance of the coils equals the distance to the fault, as half the electricity will pass by each route. But if the length of the cable wire to the fault be less or greater than the coil resistance interposed, its galvanometer needle will be more or less deflected by it than the other is by the bobbin wire, according as its length is less or greater. By varying the number of resistance coils and consequently their representative mileage, until they balance the resistance of the cable to the point of leakage, the distance of the fault can thus be determined.
To shew how thoroughly perfect the insulation is of both cables, the extremities of the two conducting wires which now stretch across the Atlantic were joined together in Newfoundland, so as to form au immense unbroken loop-line of three thousand seven hundred miles. Some acid was then put in a lady's silver thimble with a small piece of zinc and another of copper, and by this simple agency signals were passed the entire length of both cables in little more than a second of time. Of course the success of an experiment like this was possible only with a conductor as large and as wonderfully perfect in insulation as that of the Atlantic cables. The feat, however, forms a strange contrast to the enormous electrical power used in working the cable of 1858, when at first the intense secondary currents derived from the inductive action of fifty cells of a very large battery were employed; and afterwards a power equal to five hundred cells, producing a current almost akin in its effects to lightning! There is no doubt that with the comparatively small conductor and poor insulation of the 1858 cable, an unusually high power was requisite to drive the signals through in tolerably quick succession to form messages; but this energetic force soon wrought destruction to the very channel through which it passed, much as its prototype lightning blasts and destroys the conducting fibres of the tree by which it is conveyed to the earth.
Subsequently the Superintendent at Newfoundland actually passed distinct signals with a battery composed of a copper percussion cap and a small strip of zinc, which were excited by a single drop of acidulated water.
In the concluding remarks the lecturer stated that the Atlantic telegraph would have uses scarcely anticipated. As an illustration he mentioned that, immediately after the cable was laid, a message was sent announcing a birth in America to be advertised in the London Times, and it was published the day following. One of the most expensive messages sent was a report of 800 words from the London correspondent of the New York Herald, descriptive of the fight for the championship between Mace and Goss! Another message of a somewhat similar length recorded the King of Prussia's speech at the opening of the Chambers after the Austrian war; but by far the most expensive message of all was one sent in cypher by the authorities at Washington to the American ambassador at Paris—a message costing £4000.
The charge for transmission was at first restrictive, the Company being fearful of blocking up the cables. For three months the tariff was £20 for a message of twenty words; but notwithstanding this almost prohibitory rate of £l per word, a large number of messages were transmitted, including the long dispatches referred to. The tariff was reduced on the 1st November to £10 per twenty words.
To further illustrate the techniques used in the recovery of the 1865 cable, this broadside published in England in 1866 provides a more detailed view of the scene described by Edward Bright in the paper above.