To connect the telegraph to anywhere outside Britain, submarine telegraph cables were needed. The lack of a good insulator held back their development.
Rubber was tried but degraded in salt water. The solution came with
gutta-percha, a natural
latex from trees of the genus
Palaquium in the Far East. It sets harder than rubber when exposed to air, but when soaked in hot water it becomes plastic and mouldable. On cooling it rehardens.
William Montgomerie, the head of the medical department in
Singapore, brought the material to the attention of the
Royal Society in 1843 when he sent samples of Gutta-percha to them. Montgomerie thought of using the material, in place of rubber which deteriorated rapidly in damp tropical conditions, to make medical equipment. After testing some samples, Michael Faraday recognised its potential for underwater cables. Wheatstone introduced plans in the
House of Commons for submarine cables as early as 1840. In 1844–1845, he tested (probably short) lengths of cable in
Swansea Bay. He tried various insulations, including gutta-percha, but he could not find a suitable way of applying it to long runs of cable.
Cable manufacturing companies The
Gutta Percha Company was founded in 1845 to exploit the new material. They initially made bottle stoppers, but soon expanded to a wide range of products. In 1848, on hearing of its potential use for telegraph cables, the firm modified a machine for extruding gutta-percha tubing into one capable of continuously applying gutta-percha to a copper conductor. Up to 1865, the Gutta Percha Company, which had a monopoly on the supply of the material, made nearly all the cores for submarine cables in the UK.
S. W. Silver and Co. in
Silvertown, London, made waterproof clothing using rubber and gutta-percha. In 1864, an offshoot of Silver and Co., the
India Rubber, Gutta Percha and Telegraph Works Company, was founded as a rival cable manufacturer. Some early submarine cables were laid with just their insulation for protection. This was often unsuccessful. The cables were easily damaged and some attempts to lay them failed because they would not sink. The configuration found to work well was to twist the cable cores together, bind them with tarred
hemp, wind a tarred cord around the whole group of cores, and then protect the assembled cores with iron wires twisted around them. The Gutta Percha Company never made completed cables of this sort, sending them to another company for finishing instead. These companies were specialists in the manufacturing of wire rope.
R.S. Newall and Company in
Tyne and Wear,
Glass, Elliot & Company, and
W. T. Henley in London. were the principal companies involved in this early work. In 1864, the Gutta Percha Company merged with Glass, Elliot to form the
Telegraph Construction and Maintenance Company (Telcon).
John Pender instigated this becoming chairman. Pender, with a consortium including
Thomas Brassey and
Daniel Gooch, bought the
SS Great Eastern, a huge, failing passenger ship built by
Isambard Kingdom Brunel. They converted it into a
cable layer. Telcon chartered the ship using it on some of the major cable installations around the world. By 1880, cable production was centred on the banks of the
Thames in
East London. Telcon was the major supplier, with some work subcontracted to W. T. Henley at
North Woolwich, a major manufacturer of electrical equipment with a site. Gutta-percha production was near-monopolised by the India Rubber, Gutta Percha and Telegraph Works Company, by then a subsidiary of Telcon, at their site in Silvertown. The company operated several cable ships, of which the
Silvertown was the largest in the world.
Siemens also had a cable manufacturing facility at
Woolwich. Exports were a large part of the business totalling well over £2 million in 1873—one per cent of total British manufactured exports.
Ocean cable companies The world's first ocean cable was laid across the
English Channel.
Jacob and John Watkins Brett had been planning such a cable since 1847. In 1849, the
South Eastern Railway Company conducted a trial of of cable made by the Gutta Percha Company from the ship
Princess Clementine anchored off
Folkestone. The ship could send telegraph messages directly to London via a connection to the South Eastern's overhead telegraph line. After several failed attempts, the Bretts' company, the Submarine Telegraph Company (STC), succeeded in connecting to France in 1851. The company went on to lay many other cables to European countries. The Magnetic had a close relationship with the STC. From about 1857, the two companies had an agreement that all STC submarine cables were to be used only with the Magnetic's landlines. The Magnetic also controlled the first cable to Ireland. This control of international traffic gave them a significant advantage in the domestic market. Both Newall and Glass, Elliot laid cables as subcontractors to the inland telegraph companies. Newall was prone to fall out with his customers and was often involved in litigation resulting in the company slowly moving away from the telegraph cable business. The British government took a strong interest in the provision of international telegraph connections. Government assistance to telegraph projects included the provision of
Royal Navy ships to assist with cable laying and monetary guarantees. Two major failures gave them cause for concern—the first
transatlantic telegraph cable, laid in 1858 by the
Atlantic Telegraph Company, and the
Red Sea to India cable in 1859 laid by the Red Sea & India Company. The transatlantic cable's insulation failed after a few weeks. The cable to India (manufactured and laid by Newall) was too thin and laid taut over underwater peaks which soon broke it in multiple places. The guarantees provided by the government for these two ventures led to a financial loss. In response, a government committee was formed in 1859 to investigate the issue. In their final report in 1861, the committee concluded that future failures of this kind were avoidable now that the technology was better understood. They recommended specifications for future cable construction, installation, and maintenance. After the Red Sea failure, the government no longer provided subsidies or guarantees and left it to private companies to assume the risk of new ventures entirely. Getting a telegraph connection to India was a priority for the government after the
Indian Mutiny of 1857; the urgent telegram requesting assistance had taken forty days to reach London. The telegraph went only as far as the coast of India and from there the message travelled by ship. The failure of the first cable was a significant blow. A connection to India was finally achieved in 1864 after the
Indian government had laid a new cable made by W. T. Henley from
Karachi to
Fao, Iraq, and the using overland routes. This ocean route was a shorter distance than the Red Sea route and in shallower water, but still . Many times longer than any other submarine cables, this was the first extremely long submarine cable to be a permanent success. The British government believed the telegraph would provide the means for much greater central control of overseas possessions. Colonial officials necessarily had a great deal of latitude for independent action due to the communication delay. The telegraph greatly restricted their independence, although it took some time for embedded attitudes to change. Pender's motivation in creating Telcon from the merger of Glass, Elliot and the Gutta Percha companies was to create a company that could make and maintain the second transatlantic telegraph cable for the Atlantic Telegraph Company. It was also his motivation for buying
Great Eastern, the only ship capable of holding all the required cable. With great difficulty, the transatlantic connection was achieved by 1866, creating a truly worldwide telegraph network. London could now communicate with most other telegraph offices in the world. In 1862, a new submarine cable had been laid from
Queenstown in southern Ireland to
St David's Head in Wales. When this was connected to the transatlantic landing point at Valentia Bay (opposite
Valentia Island), it dramatically reduced the distance transatlantic messages had to travel from Ireland to London from to . The success of the transatlantic cable triggered the formation of many new companies to lay more submarine cables around the world. Pender founded most of these companies. His first project was to lay a new cable to India that covered most of the distance in international waters. This put it fully under British control, avoiding the political and other risks associated with an overland route. Telcon manufactured the cable and used the
Great Eastern to lay it. To limit the risk, Pender founded three companies, each tasked with laying one section of the cable. The Anglo-Mediterranean Company (founded 1868) laid a cable from
Malta to
Alexandria in Egypt. From there, a short overland cable via
Cairo connected to
Suez. The Falmouth, Gibraltar and Malta Telegraph Company (founded 1869) connected Malta to
Porthcurno, Cornwall, with landings at
Gibraltar and
Carcavelos, Portugal. The company was so named because
Falmouth was originally intended as the landing site in England. The tiny village of Porthcurno became the largest submarine cable station in the world after numerous other cables were landed there. In 1870, the British-Indian Submarine Company (founded 1869) provided the final link from Suez via
Aden to
Bombay. Once the connection was complete, the three companies were merged as the
Eastern Telegraph Company in 1872.
James Anderson, the captain of the
Great Eastern, was made managing director. The British-Indian Submarine Extension Company laid a cable going east from India in 1871. This ran from
Madras, which was connected overland to Bombay, to
Singapore via
Penang and
Malacca. This met a cable in Singapore laid by the China Submarine Telegraph Company (founded 1869) running to
Hong Kong. The British-Australian Telegraph Company (founded 1870) then connected Hong Kong to
Port Darwin, Australia, via
Java. This was the end point of the
Australian Overland Telegraph Line, running to
Port Augusta in
South Australia. The three companies were merged as the Eastern Extension, Australasia and China Telegraph Company in 1873. This company connected Australia to New Zealand in 1876. Other Pender companies included: the Western and Brazilian Telegraph Company (1873), the Brazilian Submarine Telegraph Company (1873), Marseilles, Algiers and Malta Telegraph Company (1870), Eastern & South African Telegraph Company (1879), and the African Direct Telegraph Company (1885). These companies were all merged into the Eastern Telegraph Company, which became the Eastern and Associated Cable Company—the largest multinational of the 19th century. The development of the undersea telegraph cable network began in the late nineteenth century. In October 1902, a worldwide network of cables and relay stations—including some 100,000 miles of undersea cables—was inaugurated. Called the
All Red Line, because at that time British territories and colonies were usually coloured red or pink on maps, it carried long-distance telecommunications to all parts of the British Empire. The idea was to create a network that did not pass through any non-British territory to avoid security and political risks. In 1928, British submarine cables still dominated world telecommunications, but they were increasingly under threat from
radiotelegraphy. A particular concern was
RCA in the US, but they were also losing business because of the
Imperial Wireless Chain set up by the British government to connect the empire. The
Marconi Wireless Telegraph Company, which was also a competitor outside the Empire, supplied the transmitters for the Imperial Chain. The Electra House Group, an informal alliance of British telecommunication companies, decided that they could best compete worldwide by merging their cable and radio companies into a single entity. Thus, the Eastern Telegraph Company and the Marconi Wireless Company were merged into Imperial and International Communications Ltd, which changed its name to
Cable & Wireless Ltd in 1934. The Porthcurno station remained open for exactly one hundred years, closing in 1970 when the last cable was taken out of service. Submarine
coaxial cables with
repeaters, which carried multiple telephone channels using
frequency division multiplexing, had been in use for some time. By then, there was no real need for distinct telegraph cables. Telegraph was declining, and multiple telegraph channels could be multiplexed into a single telephone channel since the 1920s. The Porthcurno Cable Hut where cables were landed is now the
Porthcurno Telegraph Museum and the historic archive of Cable & Wireless.
Maintenance and technical problems Maintenance costs of submarine cables were high. Ships' anchors frequently damaged them, and their insulation deteriorated over time. They were most at risk in shallow water near the coast, but very deep water was avoided because it was difficult to retrieve cables for repair. In 1868, the expected life of a cable was fifteen years, and most laid to that date had not lasted that long. A similar problem with deteriorating insulation plagued buried inland cables, the Magnetic suffering the most from this. A recurring problem with buried cables, and most especially submarine cables, was the phenomenon of
dispersion, which produces the effect called
retardation. Dispersion, as it relates to
transmission lines, is different
frequency components of a signal travelling along a line at different speeds. Early telegraph engineers did not understand frequency analysis of this sort. The effect of dispersion on a telegraph pulse is to spread it out in time. This is because a rectangular pulse (as used in telegraphy) has multiple frequency components. At the receiving end it appears as if part of the pulse has been retarded, hence the term. The problem this causes for telegraphy is that adjacent pulses smear into each other, an effect called
intersymbol interference by modern engineers, and if severe enough the message cannot be read. It forces the operator to slow the speed of sending so that there is again separation between the pulses. The problem was so bad on the first transatlantic cable in 1858 that transmission speeds were in minutes per word rather than words per minute. Thinking he could solve the problem by using a higher voltage, telegraph engineer
Wildman Whitehouse only succeeded in permanently damaging the cable, making it unusable. This failure represented a loss of nearly £2 million (£ million in )) for the Atlantic Telegraph Company. Retardation is worse in insulated cables because the
electromagnetic wave is travelling mostly in the insulation material. Uninsulated wires on overhead poles, the most common system on overland routes, are largely unaffected, even over long distances. This solution is not open to submarine cables and the very long distances maximise the problem. The problem of retardation was not fully solved until the introduction of long-distance telephony made it essential to do so. However, various mitigating actions were taken. The Magnetic, operating a large number of buried cables, had an instrument that sent a delayed pulse of opposite polarity to the main pulse, cancelling the worst of the retarded signal. The
mirror galvanometer designed by
Lord Kelvin made it easier to read weak signals, and larger cables with thicker insulation had less retardation. In 1854, Kelvin produced a
mathematical description of retardation by analogy with heat flow after the fiasco with the first transatlantic cable. In 1881,
Oliver Heaviside gave the
full analysis of transmission lines which described how the problem arose and suggested how it could be resolved n 1887. Heaviside believed that adding the right amount of
inductance to the line would completely remove the dispersion effect. He tried to persuade the
General Post Office (the Post Office) to take up the idea, but as an outsider—and considered a maverick—he was ignored, largely because of his long-running dispute with
William Preece, the Post Office chief electrician (chief engineer). It was left to
George Ashley Campbell in the US to implement the idea when he added
loading coils to a telephone line for the first time in 1900. == Employment of women ==