Technology & Medicine › Industrial revolution › Electric telegraph
Transatlantic telegraph cable
1858 (failed after weeks); lasting from 1866· Invention or discovery· Communication & computing
Well documentedSolid records, physical evidence or scientific consensus.
A telegraph cable laid across the Atlantic seabed, cutting message times between Europe and North America from days to minutes.
See it on the Technology & Medicine map →How it works
Backed by American businessman Cyrus Field, the first cable, from Valentia Island, Ireland, to Newfoundland, opened in August 1858. Queen Victoria's 98-word greeting took about 16 hours to send, and the line failed within a month. After an 1865 attempt snapped, the giant steamship Great Eastern laid a lasting cable in July 1866. Physicist William Thomson, later Lord Kelvin, supplied the theory and sensitive receivers. Early speeds were about eight words a minute.
Why it mattered
It joined European and American markets, newspapers and governments in near real time, the first link in today's global undersea network.
How we know
Company records, newspaper coverage, Thomson's scientific papers and surviving cable samples; Tiffany & Co. sold souvenir pieces of the 1858 cable.
Connections (3)
▸Steamships laid the Transatlantic telegraph cableWell documented
The connection
Laying about 2,000 miles of heavy cable needed big, steady ships. In 1858 two steam-assisted warships spliced their cable halves mid-ocean. In 1866 Brunel's Great Eastern, the only ship big enough to carry a whole cable, laid the lasting line, then grappled up and finished the lost 1865 cable.
When and how
1857–58: HMS Agamemnon and USS Niagara; 1865–66: the Great Eastern, from Valentia Island, Ireland, to Heart's Content, Newfoundland.
How we know
Ships' logs, newspaper reports and engravings of the expeditions; the Great Eastern went on to lay several more ocean cables.
Debates and open questions
Historians debate whether the Great Eastern was essential or merely convenient, since two ships splicing mid-ocean had already laid the 1858 cable.
▸Electric telegraph spanned the ocean with the Transatlantic telegraph cableWell documented
The connection
Land telegraphs already linked cities in minutes, but news between Europe and America still took about ten days by ship. An ocean cable needed gutta-percha, a tree latex, for insulation, plus William Thomson's theory of signal delay and his sensitive mirror galvanometer to read faint, smeared pulses.
When and how
Cyrus Field's Atlantic Telegraph Company, 1856; William Thomson, later Lord Kelvin, in Glasgow; the first lasting undersea cable crossed the English Channel in 1851.
How we know
Thomson's published papers on signal delay, company records, and the 1858 exchange between Queen Victoria and President Buchanan.
Debates and open questions
Whether the 1858 cable failed mainly because electrician Wildman Whitehouse applied excessive voltage, or from poor manufacture and storage, is still argued.
▸Transatlantic telegraph cable pioneered the undersea cables of The Internet (TCP/IP)Well documented
The connection
The 1866 cable began a worldwide web of undersea cables; by 1900 they linked every inhabited continent. Fiber-optic cable replaced copper from 1988. Today roughly 99% of intercontinental internet traffic travels through several hundred undersea cables, laid by specialist ships much as the Great Eastern did.
When and how
Atlantic, 1866; first transatlantic fiber cable, TAT-8, 1988; today's cables are owned by telecom groups and tech firms such as Google and Meta.
How we know
Industry maps such as TeleGeography's count over 500 active and planned cables; the 99% figure is a widely cited industry estimate.
Debates and open questions
How vulnerable these cables are to accidents and sabotage, after several cuts in the Baltic and Red Sea since 2023, is debated.