Transatlantic telegraph cables are undersea cables running under the Atlantic Ocean which were used for telegraph communications.
The Atlantic Telegraph Company led by Cyrus West Field constructed the first transatlantic telegraph cable. The project began in 1854 with the first cable laid from Valentia Island off the west coast of Ireland to Bay of Bulls, Trinity Bay, Newfoundland. The first communications occurred on August 16, 1858, but the line speed was poor. The first official telegram to pass between two continents that day was a letter of congratulations from Queen Victoria of the United Kingdom to President of the United States James Buchanan. Signal quality declined rapidly, slowing transmission to an almost unusable speed. The cable was destroyed after three weeks when Wildman Whitehouse applied excessive voltage to it while trying to achieve faster operation. It has been argued that the cable's faulty manufacture, storage and handling would have caused its premature failure in any case. Its short life undermined public and investor confidence and delayed efforts to restore a connection.
The second cable was laid in 1865 with improved material. It was laid from the ship SS Great Eastern, built by John Scott Russell and Isambard Kingdom Brunel and skippered by Sir James Anderson. More than halfway across, the cable broke, and after many rescue attempts, it was abandoned. In July 1866 a third cable was laid from The Anglo-American Cable house on the Telegraph Field, Foilhommerum. On July 13, Great Eastern steamed westward to Heart's Content, Newfoundland, and on July 27 the successful connection was put into service. The 1865 cable was also retrieved and spliced, so two cables were in service. These cables proved more durable. Line speed was very good, and the slogan "Two weeks to two minutes" was coined to emphasize the great improvement over ship-borne dispatches. The cables altered the personal, commercial and political relations between people across the Atlantic. Since 1866, there has been a permanent cable connection between the continents.
In the 1870s, duplex and quadruplex transmission and receiving systems were set up that could relay multiple messages over the cable. Before the first transatlantic cable, communications between Europe and the Americas had occurred only by ship and could be delayed for weeks by severe winter storms. By contrast, the transatlantic cable made possible a message and response on the same day.
In the 1840s and 1850s several people proposed or advocated construction of a telegraph cable across the Atlantic, including Edward Thornton and Alonzo Jackman.
As early as 1840 Samuel F. B. Morse proclaimed his faith in the idea of a submarine line across the Atlantic Ocean. By 1850 a cable was run between England and France. That year, Bishop John T. Mullock, head of the Catholic Church in Newfoundland, proposed a telegraph line through the forest from St. John's to Cape Ray and cables across the Gulf of St. Lawrence from Cape Ray to Nova Scotia across the Cabot Strait.
Around the same time, a similar plan occurred to Frederic Newton Gisborne, a telegraph engineer in Nova Scotia. In the spring of 1851 he procured a grant from the Newfoundland legislature and, having formed a company, began building the landline.
In 1854, businessman and financier Cyrus West Field and Gisborne discussed the project. Afterward, Field considered the idea that the cable to Newfoundland could be extended across the Atlantic Ocean.
Field was ignorant of submarine cables and the deep sea. He consulted Morse and Lieutenant Matthew Maury, an authority on oceanography. The charts Maury constructed from soundings in the logs of multiple ships indicated that there was a feasible route across the Atlantic. It seemed so ideal for cable laying that Maury named it Telegraph Plateau. Maury's charts also indicated that a route directly to the US was too rugged to be tenable and considerably longer. Field adopted Gisborne's scheme as a preliminary step to the bigger undertaking and promoted the New York, Newfoundland and London Telegraph Company to establish a telegraph line between America and Europe.
The first step was to finish the line between St. John's and Nova Scotia, which was undertaken by Gisborne and Field's brother, Matthew. In 1855 an attempt was made to lay a cable across the Cabot Strait in the Gulf of Saint Lawrence. It was laid out from a barque in tow of a steamer. When half the cable was laid, a gale rose, and the line was cut to keep the barque from sinking. In 1856 a steamboat was fitted out for the purpose, and the link from Cape Ray, Newfoundland to Aspy Bay, Nova Scotia was successfully laid. The project's final cost exceeded $1 million, and the transatlantic segment would cost much more.
In 1855, Field crossed the Atlantic, the first of 56 crossings in the course of the project, to consult with John Watkins Brett, the greatest authority on submarine cables at the time. Brett's Submarine Telegraph Company laid the first ocean cable in 1850 across the English Channel, and his English and Irish Magnetic Telegraph Company had laid a cable to Ireland in 1853, the deepest cable to that date. Further reasons for the trip were that all the commercial manufacturers of submarine cable were in Britain, and Field had failed to raise significant funds for the project in New York.
Field pushed the project ahead with tremendous energy and speed. Even before forming a company to carry it out, he ordered 2,500 nautical miles (4,600 km; 2,900 mi) of cable from the Gutta Percha Company. The Atlantic Telegraph Company was formed in October 1856, with Brett as president and Field as vice president. Charles Tilston Bright, who already worked for Brett, was made chief engineer, and Wildman Whitehouse, a medical doctor self-educated in electrical engineering, was appointed chief electrician. Field provided a quarter of the capital himself. After the remaining shares were sold, largely to existing investors in Brett's company, an unpaid board of directors was formed, which included William Thomson (the future Lord Kelvin), a respected scientist. Thomson also acted as a scientific advisor. Morse, a shareholder in the Nova Scotia project and acting as the electrical advisor, was also on the board.
The main ocean section of the cable consisted of a seven-strand copper core, covered by four layers of gutta-percha, wrapped in tarred hemp, and protected by ten steel wires wrapped in impregnated hemp. Thomson modeled the submerged cable as a very long wire conductor along the axis of a cylinder of perfect electrical insulation, forming two concentric conducting cylinders as in a coaxial cable. The inner conductor was the telegraph line while the outer conductor consisted of the insulator and seawater interface. In 1854, Thomson introduced electrostatical capacity, and resistance, per unit length to derive an equation defining voltage at time t and distance x along the cable. His analysis resulted in his law of squares and the dispersive nature of the cable. In 1876, Heaviside introduced inductance per unit length to Thomson's work, leading to the insight needed to mitigate the phase-distortion problem.
The wires, each weighing 26 kg/km (107 pounds per nautical mile), were covered with gutta-percha as suggested by Jonathan Nash Hearder), weighing 64 kg/km (261 pounds per nautical mile). The overall cable weighed nearly 550 kg/km (1.1 tons per nautical mile), was relatively flexible, and could withstand tension of several tens of kilonewtons (several tons).
The cable from the Gutta Percha Company was armoured separately by wire-rope manufacturers, the standard practice at the time. In the rush to proceed, only four months were allowed for the cable's completion. As no wire-rope maker had the capacity to make so much cable in such a short period, the task was shared by two English firms: Glass, Elliot & Co. of Greenwich and R.S. Newall and Company of Birkenhead. Late in manufacturing, it was discovered that the two batches had been made with strands twisted in opposite directions. This meant that they could not be directly spliced wire-to-wire, as the iron wire on both cables would unwind when it was put under tension during laying. The problem was solved by splicing through an improvised wooden bracket to hold the wires in place, but the mistake created negative publicity for the project.