From experiments to a network
The 1830s did not give the world a global telegraph. They gave it working prototypes, which is a different thing. The decade saw experimental systems built in Russia by Pavel Schilling, in Göttingen by the scientists Carl Friedrich Gauss and Wilhelm Weber, and in Britain and the United States by the people who would later be credited with practical commercial telegraphs. In 1837 William Cooke and Charles Wheatstone patented a system in Britain, and Samuel Morse was developing his own in the United States.
A global network took another three decades. The path was gradual: first short lines beside railways, then national networks, then links under rivers and straits, and finally lines across the open ocean.
Land lines first
In Britain, early telegraph wires ran alongside railway lines in the late 1830s, and by the 1840s public telegraph companies were opening offices in towns. In the United States, a line between Washington and Baltimore opened in 1844, and private companies quickly built others. Cities, ports and railway junctions were joined by the early 1850s, and a transcontinental line across the United States was completed in 1861.
Elsewhere, governments often took the lead. Telegraphs were laid across much of continental Europe, and in India a system was developed in the 1850s under British administration. The telegraph reached remote places faster than any earlier technology, although people could still be many hours or days from the nearest telegraph office.
The problem of water
Rivers and seas were an obstacle. Overhead wires could span narrow rivers, but wide water required cables laid on the bottom. The difficulty was insulation: a copper wire in salt water would leak its signal to the surroundings.
The material that made submarine cables practical was gutta-percha, a natural latex from trees in Southeast Asia, which could be softened by heat, molded around a wire, and hardened again. It was introduced to Europe in the 1840s and quickly adopted as cable insulation. It resisted water well, although it was far from perfect.
A short cable between Dover and Calais was laid in 1850 and worked briefly before failing. A stronger version with armor wires was laid in 1851, and it lasted. By the middle of the 1850s, a patchwork of cables crossed the Channel, the Irish Sea, the North Sea and other narrow waters.
The Atlantic cables
The great challenge was the Atlantic. The American businessman Cyrus Field led efforts to raise money and organize a cable, with engineers and scientists in Britain and the United States contributing. Laying cable from ships across a 2,000-mile stretch of ocean meant handling hundreds of tons of cable in rough weather, with ships that were mostly powered by sail or modest steam engines.
Several attempts failed when the cable snapped or when the signal was lost. A cable completed in 1858 carried messages, including ceremonial exchanges between Queen Victoria and President James Buchanan, but it deteriorated after a few weeks and then stopped working. Reports agree that transmitting the opening message took many hours.
Another attempt in 1865 failed when the cable broke during laying. In 1866 the ship Great Eastern, a huge vessel built for the purpose of such tasks, completed a new cable and then went back to recover and finish the broken cable from the year before. The 1866 cable worked, and it was a lasting success. Transatlantic messages that once needed roughly ten days by steamship could now arrive in minutes.
Signals through a long cable
Transmission through a long submarine cable was more difficult than through an overland wire. Signals became blurred and slow, which limited how many messages the line could carry. Better receiving instruments, including sensitive galvanometer-based devices developed by William Thomson, later Lord Kelvin, helped operators read weak signals. Larger copper conductors improved performance too.
The batteries used at the sending end were descendants of the voltaic pile, and the power needed was modest, but the receiving end had to detect very small currents.
Connecting continents
After 1866, cables multiplied. By the early 1870s a chain of lines linked Britain with India, and then Australia. Messages that once took weeks or months by sailing ships, fast clipper ships and steamers now moved in hours. Prices stayed high, so businesses, governments and news agencies were the main users.
The telegraph map also shaped geopolitics. Governments cared about who owned cables, where they landed, and whether they could be cut in a war. Britain gained a particular advantage from its extensive cable network, a point that mattered in later conflicts.
What the cables meant
Within about thirty years of Morse and Wheatstone, a message could cross the world in a day or so, passing through several operators. The effect on news, trade and diplomacy was large. The idea of a single worldwide communication system took hold, and later technologies, including fibre optic communications that carry most of today’s international traffic along similar sea routes, built directly on the cable engineering developed in this period.