Communicating Underwater

Michal Meyer

In his 1869 futuristic novel, Twenty Thousand Leagues under the Sea, Jules Verne imagined a marvelous electric-powered submarine that explored the mysterious underwater world and its inhabitants. Late in the book the main protagonist, Pierre Aronnax, rhapsodizes over a particular undersea marvel—an electric cable lying on the bottom of the North Atlantic Ocean. Unlike the fictional submarine, the Nautilus, the cable actually existed in the nonfictional world. It was the first major link in what was to be a 19th-century ocean-spanning global communications network that Victorians predicted would prevent misunderstandings between nations, banishing war forever. This physical network, along with less benign attempts at empire building, owed its existence to the coagulated latex of a tree native to Southeast Asia.

All efforts to insulate these wires proved unsuccessful until 1847, when Siemens and a collaborator developed a method to permanently insulate wires by pressure-coating them with gutta percha.

In the early 19th century several ways existed to communicate over large distances: homing pigeons, messengers on foot or horse, and even signals using flags or lights. But within 20 years of Alessandro Volta’s invention of the battery in 1800, speculation flowed on how to use electric current to communicate over distances by stopping and starting current in a wire. After William Cooke and Charles Wheatstone built the first railway telegraph in Britain in 1837, the new technology (modified by Samuel Morse) spread quickly throughout Britain, France, Germany, and the eastern United States. Yet Britain, a commercial empire, faced a seemingly insurmountable problem: as an island it could not electrically connect itself to the continent.

Early attempts at insulating wire against water with tarred hemp or India rubber failed. Hope arrived in the form of the milk-colored sap of a Malaysian Palaquium gutta tree. The sap, called gutta percha, is a naturally occurring structural isomer of polyisoprene, also known as “natural rubber” or isoprene rubber, with enough flexibility to bend with a wire when heated and retain its shape when cooled. Gutta percha is also tough, easily absorbing stress at the temperatures found on land or at the bottom of the sea. And equally as important, it is a remarkable electrical insulator.

In 1843 William Montgomerie, a British surgeon in Asia, sent samples of gutta percha to England. The sap came to the attention of William Siemens, a London-based German who forwarded the substance to his brother, Werner, who realized its electrical potential. A Prussian artillery officer with a scientific bent, Werner Siemens was involved in the military’s switch from optical to electric telegraphy. In Prussia engineers laid wires underground, where they were subject to rats’ teeth and damp soil. All efforts to insulate these wires proved unsuccessful until 1847, when Siemens and a collaborator developed a method to permanently insulate wires by pressure-coating them with gutta percha. During the 1848 revolution, to protect against Danish naval incursions, Siemens laid submarine mines connected via gutta percha–insulated wires to a detonator in Kiel Harbor. Though never used to blow up ships, this first underwater use of gutta percha foreshadowed its later military roles.

In 1850 British enthusiasts laid the first submarine cable between England and France. The cable, a 25-nautical-mile strand of copper wire surrounded by gutta percha, transmitted a message to the future French emperor Napoleon III but failed within a few hours after a fisherman hauled up the wire accidentally and broke it. The next year an armored cable was successfully laid between the two countries and proved both popular and profitable. News of events—of arriving and departing ships and their cargoes, and of prices for goods—sped across the English Channel on this cable faster than the wings of carrier pigeons. (The cable worked for 37 years, in spite of such early testing methods as using an engineer’s tongue to measure current.)

Despite its German origins in Kiel Harbor and Siemens’s undoubted talents, undersea cables became almost a solely British industry, thanks to Britain’s lock on gutta-percha supplies and its growing need to keep its world-spanning empire connected. By 1900 the British Secretary of the Treasury described the ocean-crossing cables as the “true nerves of the Empire.”