The Atlantic Cable of 1866: Making Transoceanic Communication a Daily Service

An Atlantic cable connected Ireland and Newfoundland in 1858, but communication soon failed. In 1865, Great Eastern again lost a cable during laying. By 1866, the question was no longer simply whether electricity could cross the ocean, but whether manufacturing, laying, repair, and paid operation could become a reliable business.

Cyrus Field continued raising money on both sides of the Atlantic, while the Anglo-American Telegraph Company organized and financed the new undertaking. Britain's Telegraph Construction and Maintenance Company manufactured and laid the cable. Managers, crews, electrical specialists, and investors had interlocking responsibilities: factories had to supply sound cable, ships had to pay it out safely, and shore stations had to connect the submarine line to existing land networks.

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The cable's central copper conductor carried signals, surrounding gutta-percha excluded seawater, and fiber and iron wire provided protection. The cables used in 1865–1866 had conductors made of multiple copper wires, covered with insulation, hemp bedding, and galvanized iron wire. Electrical performance and mechanical strength both had to meet requirements; a cable functioning electrically in the factory could still be bent, strained, or punctured by foreign objects aboard ship.

Manufacture and loading were therefore not merely preliminaries. Joints between lengths had to preserve electrical continuity and insulation, and testing continued after loading into Great Eastern's large cable tanks. Workers also had to watch for tangles as cable paid out. Thicker conductors, more substantial insulation, and more sensitive testing than in 1858 were all improvements learned from failure.

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In July 1866, the line set out from Foilhommerum Bay near Ireland's Valentia Island, bound for Heart's Content in Newfoundland's Trinity Bay. Great Eastern could carry a large quantity of cable, reducing the difficulties of joining lines from two vessels in mid-ocean. Captain James Anderson managed navigation and engineer Samuel Canning the laying operation. Ship speed, braking equipment, and cable tension had to be coordinated; the process was not simply dropping a line into the sea.

Cable paid out over the stern while electricians monitored continuity and insulation. Shore stations sent messages through the cable still connected to the ship, making testing a rehearsal of actual communication. When anomalies appeared, personnel had to decide whether to stop, recover cable, or splice in a repair. Excessive tension could break the line, while paying out too much wasted material and increased risk. On July 27, the new cable reached Newfoundland, and the shore connection restored transatlantic communication.

Testing organized by electrician Willoughby Smith integrated ship and shore into one procedure. Onshore personnel changed circuit conditions at scheduled times while those aboard observed instrument responses to check conductor continuity. Insulation tests helped identify current leaking into seawater. Detecting abnormalities before faults grew was more valuable than waiting to inspect the entire line after completion.

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After completing the new cable, the fleet returned to the area where the 1865 line had broken. Deep-sea recovery relied on position records, towed grapnels, steel ropes, and buoys. Hooking the cable did not guarantee success, because it might break and fall again while being raised. After repeated attempts, crews brought the recovered end to the testing room, confirmed communication with Ireland, spliced on fresh cable, and laid it toward Newfoundland.

In September, the recovered cable also became a working connection. The achievement of 1866 was therefore more than one fortunate laying operation: it included successful recovery from failure. For operators, another usable cable strengthened service security; for engineers, submarine lines began changing from expensive objects whose survival depended on hope into facilities that could be repaired.

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William Thomson's mirror galvanometer made weak currents visible through the movement of a spot of light. After a successful connection, telegraphists still had to recognize signals, transcribe words, check messages, and forward them to cities over landlines. The ocean cable shortened transmission time but did not remove constraints caused by broken shore connections, manual relays, or tariffs.

Merchants, newspapers, and governments gradually gained the ability to exchange transatlantic news within the same day, without waiting for a steamship voyage for every price inquiry or reply. Early cable communication was expensive and initially served chiefly business willing to pay high rates. The crucial change in 1866 was a continuously operating channel: financing, materials, instruments, ships, and shore-station personnel sustained it together, rather than a technical demonstration ending with a celebration.

On the day the new cable arrived, another link between Newfoundland and the American mainland remained interrupted, so the news did not spread immediately throughout the United States. This episode shows that even after the longest submarine segment was complete, onward connections beyond its endpoints still determined whether users actually received telegrams.

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