The Undersea Cables

Cyrus West Field (1819–1892), American entrepreneur and telegraph promoter, obsessed with spanning the Atlantic. Field mortgaged his fortune, endured four failed transatlantic cable attempts (1857–1858), and finally succeeded in 1858, creating the first permanent telegraph link between North America and Europe. His vision outlasted ridicule, financial ruin, and technical catastrophe.

Transatlantic cables were engineered as concentric cylinders: a copper conductor (1/16 to 1/8 inch diameter) at the core, wrapped in gutta-percha insulation (1/4 inch thick), then jute or hemp yarn, then iron or steel wire armor (nine strands, each 1/16 inch). The 1858 cable weighed ~300 tons total and measured 2,000 nautical miles. Laying required specialized cable ships with massive spools and dynamometers to control tension; the SS Great Eastern (1858–1865), the largest ship afloat, became the primary cable-laying vessel. Signal attenuation over distance demanded relay stations and, later, repeater amplifiers (vacuum tubes, 1920s onward) to regenerate weakening pulses.

The first transatlantic telegraph cable was laid in 1858 after Cyrus Field's consortium raised £350,000 (approximately $1.75 million USD at the time). The initial cable failed after three weeks of operation, but a second attempt in 1865–1866 succeeded and remained operational for decades. By 1900, over 200,000 nautical miles of submarine cable crisscrossed the globe, connecting Europe, Asia, Africa, and the Americas. Telegraph cables were superseded by telephone cables (first transatlantic telephone cable, TAT-1, laid 1956), which in turn gave way to fiber-optic cables (first transatlantic fiber-optic cable, TAT-8, 1988). Undersea cables remain the backbone of global internet traffic; as of 2024, approximately 450 submarine cable systems carry ~99% of intercontinental data.

Before undersea cables, international communication relied on ships carrying mail and dispatches—a journey of 10–14 days across the Atlantic. This delay crippled commerce, diplomacy, and news dissemination. The telegraph, invented by Samuel Morse (1844), demonstrated that electrical signals could traverse land wires instantaneously. Entrepreneurs and governments recognized that submarine cables could compress global communication from weeks to seconds, enabling real-time stock trading, diplomatic negotiation, and news reporting. The cable also served imperial and commercial interests: Britain, the dominant naval and financial power, invested heavily in cables to bind its colonies and trading partners into a unified information network. By 1902, the British-controlled Imperial Wireless Chain and cable network gave London unprecedented geopolitical leverage.

Telegraph operators at shore stations received messages in Morse code, transcribed them by hand, and dispatched them via messenger. A typical transatlantic message in 1870 cost £1 per word (roughly £100 in 2024 currency) and took 1–2 minutes to transmit. Newspaper editors, stock brokers, and diplomats were the primary users. Operators worked in shifts, monitoring the cable 24 hours daily for breaks or signal degradation. The cable house—a small brick or stone building near the shore—housed the telegraph instruments, batteries, and a logbook recording every message. Maintenance crews periodically inspected the cable for corrosion, and if a break occurred, a cable ship was dispatched to grapple for the severed end, haul it aboard, splice it, and re-lay it. This process could take weeks.

Cable manufacture was a specialized industrial process. Copper wire was drawn to precise diameter at rolling mills (e.g., Siemens Brothers in London, or the Submarine Telegraph Company in New York). Gutta-percha—harvested from trees in Malaysia and Indonesia—was softened by heat and wrapped around the copper core in a continuous spiral. The insulated core was then wrapped in jute yarn and wound with steel wire armor on specialized machinery. The entire process required precision: any irregularity in diameter or insulation thickness could cause signal loss or failure. The 1858 transatlantic cable was manufactured by Glass, Elliot & Company in Greenwich, London, and took six months to produce. Laying was equally complex: the cable ship had to maintain precise speed (typically 6–8 knots) while paying out cable, accounting for water depth, currents, and the weight of the cable itself. Dynamometers measured tension continuously; if tension exceeded safe limits, the operation halted to prevent breakage.

Sections of the 1858 transatlantic cable, recovered during repair operations, are housed at the Smithsonian Institution (Washington, D.C.) and the National Museum of Ireland (Dublin). The cable exhibits the characteristic concentric layers: copper core, gutta-percha insulation, jute wrapping, and steel wire armor. Corrosion and mineral encrustation are visible on the armor. In 2010, a section of the 1865–1866 cable was recovered during maintenance and donated to the Smithsonian. Underwater archaeology has also documented cable routes on the seabed using sonar and submersible surveys; the cables themselves are largely inaccessible at depths of 10,000–16,000 feet, but their impact on the seafloor—including the trenches dug to bury them in shallow water—is visible in high-resolution bathymetric maps. No intact wreck of a cable-laying ship has been thoroughly excavated, though the SS Great Eastern was broken up for scrap in 1889.