Transatlantic Telegraph Cable Laid

In July 1866, the steamship Great Eastern completed the laying of a durable telegraph cable across the floor of the North Atlantic, linking Ireland and Newfoundland. It was not the first attempt to connect the two continents, but it was the first to deliver lasting service. Messages that had once taken ten days or more to cross the ocean by ship could now travel in minutes, transforming news, finance, diplomacy and the general sense of how far apart the Old World and the New really were.

The project was driven largely by the American businessman Cyrus Field, who organized the Atlantic Telegraph Company in the 1850s with British and American backers. Overland and short undersea telegraph lines already existed, and the idea of spanning the ocean drew on the work of engineers, electricians and scientists such as William Thomson, later Lord Kelvin, who helped refine the understanding of signals traveling along long submarine cables. Early efforts were plagued by broken lines, poor insulation and the sheer difficulty of paying out thousands of kilometers of heavy cable from ships in open water.

A cable was completed in 1858, and Queen Victoria and President James Buchanan exchanged congratulatory messages over it. Celebrations followed, but the line failed within weeks. Historians generally attribute this to a combination of weak construction and the use of excessive voltage in attempts to force signals through. The American Civil War and the need for better technology delayed further attempts until the mid-1860s. A try in 1865 using the Great Eastern, then the largest ship in the world, ended when the cable snapped and was lost in deep water.

In 1866 the expedition tried again with a improved cable and refined procedures. The Great Eastern laid a new line from Valentia Island in Ireland to Heart's Content in Newfoundland, finishing in late July. Crews then returned to the site of the 1865 failure, and over the following weeks they located and recovered the lost cable from the ocean floor, spliced it, and completed a second working link. Both lines operated, a notable feat of seamanship and engineering.

The consequences were swift. Transatlantic messages were expensive, often priced by the word, so early use focused on commerce, government and press agencies. Even so, markets in London and New York became more closely coordinated, and news from one continent could appear in the other's papers within a day. More cables followed, forming a global network that by the end of the century connected most of the world's inhabited regions. The 1866 cable is often seen as an early step toward the modern interconnected world, and its route still anticipates the undersea fiber-optic lines that carry internet traffic today.