Cooke and Wheatstone fell out spectacularly, just at the time when their electric telegraph was sweeping across Britain, over who deserved most credit. After a quiet start to life, the telegraph had suddenly leapt into the public’s consciousness. The Berkhamsted town surveyor, John Tawell, had been arrested in London after fleeing a murder scene in Slough in 1845. A description had been telegraphed to Paddington, and Tawell was quickly caught and later hanged for his crime.
As the cable spread, it became clear that it was far more than a means of catching fugitives from justice or to run railways. In the United States, a telegraph from Washington to Baltimore in 1844 marked the start of a rapidly developing network. Cables were also appearing across the continent of Europe. It was in central Europe that a remarkable career was built on the sale of information. Julius Reuter, after several false starts with his news agency, took advantage of a public telegraph between Berlin and Aachen which opened in 1849, to deliver news and prices between Berlin, Vienna and Paris. Where there were gaps between the new telegraph systems of France and Belgium, he rushed the messages by pigeon, which was faster than trains. Political and other news was an important commodity, but Reuter’s main business was trade information, prices and rates, where speed and accuracy were of the essence, and which he sold to newspapers and to commerce. He made a huge success of being ahead of the game, and moved his base to London in 1851, on the eve of the opening of the Channel cable.
The Brett brothers saw some other possibilities for international cables. When trying to raise support for their transatlantic telegraph in 1845, they pointed out to the Prime Minister, Sir Robert Peel, the advantages of instantaneous communications with all parts of the Empire. If the government did not then see how the cable could help rule the world, it did so soon afterwards when inland telegraphs proved invaluable in deploying troops and police against the Chartist threat.
The Bretts found fame as promoters of the first international submarine cable, laid between Dover and Cap Gris Nez near Calais, late in August 1850. They had obtained a ten-year concession, or monopoly, on the route. The Gutta Percha Co. supplied twenty-five nautical miles of cable. As the line was short and weighed only five tons, it could be wound around a drum and laid direct from that, using weights. This was done in a day, and messages successfully exchanged between the shores. The following day, though, there was no sign of life in the telegraph, and a French fisherman was blamed for pulling up the cable with his anchor and cutting it to take as a souvenir.
While Julius Reuter, by his pre-emptive move to London, showed faith that the cable would be completed the following year, many others did not. Ominously for the Atlantic projectors, it became clear that wild public enthusiasm could quickly give way to despair and suspicion. But compared to the Atlantic scheme, the Channel project was small fry. It was saved in 1851 by one man, a railway engineer, Thomas Russell Crampton, who raised or invested most of the £30,000 needed and also improved the design of the cable. He set a pattern for later telegraphs in using an outer protective layer of galvanised iron. The cable was successfully laid in the autumn of 1851, and remained in constant operation after that. Confidence was reborn, and, after some setbacks, other submarine lines quickly followed. By the end of 1853 there was a telegraph from Portpatrick in Wigtownshire to Donaghadee in County Down, giving the British government a valuable tool for its rule of Ireland. There were also new connections to the continent – lines from Dover to Ostend, and from Orford Ness in Suffolk to the Netherlands. The longest of these was 100 miles, the deepest 160 fathoms.
The success of these early submarine cables disguised some of their inherent flaws. On a short or shallow line, faults did not necessarily stop the telegraph from working. In the depths of the Atlantic, though, they would be fatal. At the root was the quality of the cable. Wire-drawers, even within the same factory, could not make wire to a consistent gauge or standard. But cable engineers paid little attention to the wire’s purity and electrical performance, for it was assumed that all copper wires behaved the same.
Nor was it easy to apply the gutta percha insulator evenly around the conductor. Gutta percha, an ‘imperishable subaqueous insulating material’, was heralded as the nineteenth-century wonder material. It was not a new discovery, but found a use only after Faraday during the 1840s recognised its excellent insulating properties. Electricians soon found that it worked much better than India rubber or any other compound on marine cables. Derived from the latex of gutta trees found only in the Malay peninsula, gutta percha is a natural plastic which can be shaped when hot and stays flexible as it cools. Once applied as an insulator to submarine cables, it needed to be stored in water to retain its remarkable properties. Its supremacy lasted for a century, until the advent of polyethylene-based synthetics, handing Britain, which had a monopoly on gutta percha, a long-lasting stranglehold on the production of undersea cables.
While the material itself was seen as a godsend, there was still some way to go in improving the way it was applied to the cable. With land telegraphs, most of which were carried on overhead lines, insulation was hardly an issue. The cable was insulated by glass or earthenware holders at points where it met a telegraph pole. For a submarine line, though, the insulation had to be of consistently high quality to prevent any contact between the copper conductor and the water all around.
The insulation problem turned out to be much more than a matter of waterproofing. Even when the quality of the cable was excellent, and the insulation perfectly sound, undersea cables simply did not function as expected. Messages would not pass down the line at anything like an acceptable speed without breaking down into a chaotic jumble. This electrical phenomenon came to be called ‘retardation of the signals’, sometimes known as ‘induction’. Retardation was at the root of problems with long cables, and until it could be understood and its effects overcome, the Atlantic cable could never work.
The contrast with land telegraphs was striking. By the early 1850s, overland telegraphy had achieved a measure of sophistication. Signals could be transmitted more or less automatically and at relatively high speeds. Experienced clerks understood the sound of the incoming signal almost as a language and could read off a message just by listening. Once printing receivers were introduced, the clerk no longer had to be there constantly to note down the message. Little attention needed to be given to what was happening in the conductors themselves or in the insulating envelopes. If it proved difficult to transmit intelligible signals, electrical relays could easily be inserted to boost them. This meant there was no limit to how far a telegraph line could be extended. Morse had suggested, as early as 1837, the use of relays:
Suppose that in experimenting on twenty miles of wire we should find that the power of magnetism is so feeble that it will but move a lever with certainty a hair’s breadth; that would be insufficient, it may be, to write or print, yet it would be sufficient to close and break another or a second circuit twenty miles further, and this second circuit could be made in the same manner to break and close a third circuit twenty miles further on, and so round the globe.
For most electricians, any problem of signalling came down to ‘strength of the electricity’, in other words, current. It was believed that if enough current were transmitted through the wires, there could be no difficulty in operating a receiver.
Retardation showed itself very quickly on the first submarine lines. The difficulty lay not in the speed of electrical currents in the cables, which was known to be very rapid indeed, but with the rate at which letters and words could be transmitted. During laying, the first Channel cable in 1850 was tested only for electrical continuity. When it was complete, and the time came for signals to be received from Dover, it was assumed that something was amiss with the operator:
Letters came, but they were so mixed that it was in many cases impossible to make any sense out of them … The more the operator tried to control the letters the more erratic they became. At last it was suggested that the succes
s attending the laying of the wire had caused the champagne to circulate so freely that the persons in the shore station at Dover did not know what they were doing.
It was not alcohol, but the retardation phenomenon, which was causing the problem. It was quickly confirmed that messages were being correctly sent, yet only unintelligible, chaotic signals could be received. The immediate solution was to restrict the rate at which operators worked, but this limited traffic so much that it threatened the line’s commercial viability. The electrician Willoughby Smith lamented many years later that the phenomenon of electrical induction had not been understood sooner. Looking back at the earliest undersea cables, Smith could see that the blame for their poor performance fell upon failures in scientific understanding as well as inadequate testing and quality control.
Faraday had discovered a general phenomenon called ‘the capacitance effect’ in 1838, and was able to explain how this worked to hold up underwater signals on a telegraph line. The problem had become evident again on the Channel line of 1851, and then in the cables, 100 miles in length, connecting Orford Ness with Holland in 1853. Faraday realised that a submarine cable, made from a central copper conductor surrounded by an insulating envelope of gutta percha, armoured on the outside with iron wire rope, formed an electrical capacitor. A capacitor is a device that can store electrical charge, the first practical example of which was the Leyden jar. So, when a pulse of electricity was sent into a telegraph cable, there were two processes at work: an electrical current through the core, and an accumulation of charge in the capacitor. The net effect was that it took some time before the results of a pulse applied to the input end of the cable became evident at the output. If successive pulses were too close together, confusion would result. It soon became plain that the problem of retardation was much more profound than previously understood, and that stronger currents would not solve it.
Edward Bright measured the effect in the early 1850s, clocking the speed of subterranean and submarine currents at less than 1,000 miles per second on a length of cable which was about 500 miles long. As the problem evidently intensified as the cable lengthened, electricians began to fear that it might prove to be physically impossible to send a message across the distance of the Atlantic. William Thomson wrote in 1854 that, while he had no doubt about the feasibility of successfully making and laying an Atlantic cable, a rapid rate of signalling may never be achieved. On the eve of the first transatlantic cable in 1857, scientists could attempt to describe the phenomenon but were no closer to a solution:
When the wires are enclosed in a compact sheath of insulating substance, such as gutta percha, and are placed in a moist medium, or in a metallic envelope, the influence of induction comes into play as a retarding power to a very sensible extent. So soon as the insulated central wire is electrically excited, that electrical excitement operates upon the near-at-hand layer of moisture or of metal, and calls up in it an electrical force of an opposite kind. These two different kinds of electricity then pull at each other … through the intervening layer of impenetrable insulator, and each disguises an equivalent portion of the other, that is, holds it fast locked in its own attraction and so renders it valueless as an agent of extraneous power. The inner electricity keeps the outer induced force stationary upon the external surface of the insulating sheath. The outer induced electricity keeps a certain portion of the inner, excited influence, on the interior surface of the insulating sheath as a charge, and so prevents it from moving freely onward on its journey as it otherwise would. The submarine cable is virtually a lengthened out Leyden jar … a bottle for the electricity, rather than a simple channel or pipe open freely at both ends.
While doubts persisted, submarine cables received a great boost from a national emergency, the Crimean War, which supplied the impetus and the funding for an ambitious scheme. The Crimea has been called the first modern war, and it was the telegraph that made it so. The Royal Engineers set up a circuit of twenty-one miles of cable and eight telegraph offices on the Crimean peninsula, but this was of limited use without a submarine line to link to the outside world. The cable was an instrument of war, a means of managing the conflict, but it was also to be the medium through which news of carnage and incompetence found its way back to the public of France and Britain.
The Crimean cable was in two sections, laid by Robert Stirling Newall, who had made his name as main contractor on the 1851 Channel cable and become the most prominent cable-maker and layer of the time. The main cable connected Varna in Bulgaria with Balaklava on the Crimea, a distance of 270 nautical miles and to a depth of 950 fathoms. A shorter line brought Balaklava into communication with Eupatoria, north of Sebastopol. Both these lines, commissioned by the British government and rapidly installed without armouring in 1855, were considered temporary, although they performed well until the war ended the following year. Newall also laid a line for the Ottoman government from Varna to Kilia, in the mouth of the Danube in south-west Ukraine, 150 nautical miles long and up to 500 fathoms deep, which soon failed.
Up to this point, there had only been one successful cable laid in a depth of more than 150 fathoms (about 300m). This was between La Spezia in northern Italy and Corsica, a distance of seventy nautical miles and to a depth of 325 fathoms, completed in 1854 by the Brett brothers and others for the Mediterranean Telegraph Co. This line worked without interruption for ten years. In 1855, the Bretts tried to complete the 130-mile link from Europe to North Africa with a cable from Sardinia to Algeria. The depth turned out to be more than double the estimate of 800 fathoms. After two failures, the expedition ran short of cable a few miles from Galite Island, off the Tunisian coast, and the campaign was abandoned. Newall and his partner Charles Liddell, their reputations enhanced by their work in the Crimea, were employed by the Mediterranean Telegraph Co. in 1857 for another attempt on the line in the autumn of that year, and this time were successful.
So, by late 1856, as Field and his associates prepared their assault upon the Atlantic, any lessons to be gleaned from their own and others’ experiences of deep-sea cables were far from clear. In total thirty-eight submarine telegraphs had been laid, and many of those were working well. But the ones which performed best were short and shallow. Although the Mediterranean cables were beginning to experience some success, the Italy-Corsica line was still the only one working at more than a quarter of a mile in depth. Furthermore, the retardation question remained unresolved.
It was not in Field’s nature to give up, and a great deal had already been committed to the Atlantic scheme. The Atlantic directors had to rely on assurances from their technical advisors, the electricians, who were naturally also inclined towards optimism. This was the first generation of telegraph engineers, a small group of mainly very young men who laid the foundations of what would become known as electrical engineering. Some had come out of the telegraph industry, others had academic backgrounds. As with any new technology, experience was necessarily very limited, and they struggled to understand the electrical questions which long-distance cables threw up. There was only so much that could be achieved by experiment in the factory or laboratory, so the young electricians relished any chance to carry out research on the biggest stage of all, out at sea.
For a time, though, electrical problems took a back seat. The immediate issues which needed resolving, and the ones which most fascinated the general public, were mechanical ones. It was easy to understand the challenge of handling and laying the monster cable across a vast ocean. The plan in 1857 was to start putting down the telegraph from mid-Atlantic, where the two sections would be spliced and the ships steam in opposite directions. This meant that the line could not be too heavy, for when laying started there would be a length of up to five or six miles of cable between the ships, a huge mass not immediately supported by the ocean bottom. This vast floating weight endangered the cable, and perhaps the ships themselves. Then again, the cable must not be too insubstantial, for it had to sink to the bottom under its own weigh
t. Friction, as well as the line’s own buoyancy, would act as a brake, up to a point. A line that was too light would reach the bottom, but it would not be laid straight, as currents would move it from its direct route and introduce damaging kinks.
Once the ideal weight had been established, neither too heavy nor too light, there was a question of how to deal with the cable’s bulk. How was 2,500 miles of armoured telegraph cable to be stowed and handled? It was suggested as early as 1857 that ‘Mr Scott Russell’s leviathan ship, the Great Eastern’ would be ideal for the job. Brunel’s mighty ship, an eighth of a mile in length, was under construction in John Scott Russell’s yard at Millwall on the Isle of Dogs. Unfortunately, though, the Great Eastern was incomplete – she was floated only in 1858, and finished in 1859 – so untested. ‘It must have proved its own armour, before it can be discreet to ask it to undertake a campaign for an ally.’ Two gigantic and costly experiments, the cable and the leviathan, could not be risked together.
The Cable Page 4
