Today, instant global communication is made possible by copper and fibre-optic cables carrying data under the ocean between countries.
These cables make the global Internet possible, but in fact we have relied on submarine cables for long-distance communication for over 150 years, since the first transatlantic telegraph cable allowed messages to be sent between the USA and Britain.
How was a feat like this first achieved, and what did it mean for how we communicate?
Why was a transatlantic telegraph cable needed?
By the early 1850s, telegraph networks had connected most population centres on either side of the Atlantic, including a cable beneath the English Channel to link British and French networks. Businesses eagerly anticipated a transatlantic connection.
In 1858, a new transatlantic telegraph cable shrank the world further—suddenly, messages could be sent between Europe and North America in minutes rather than days.
Queen Victoria and the President of the United States of America, James Buchanan, became the first heads of state to exchange greetings via the new transatlantic submarine cable. But disappointment soon followed—within weeks the cable failed and the connection was lost.
By that time, however, its backers had demonstrated that transatlantic telegraphy could reduce the time taken to communicate between Europe and the USA from a few weeks to less than a day. The implications for business were profound.
Who was behind the ambitious project?
Cyrus West Field, a New York paper manufacturer who had retired at the age of only 33 with $250,000 in the bank, had the energy and vision to undertake this challenge.
Laying a cable across the Atlantic would be costly and technically difficult. The shortest sea route, between the southwest coast of Ireland and Newfoundland, Canada, covered over 2000 nautical miles. By 1856 Field had set up the Atlantic Telegraph Company, with investors including both businessmen and the US and British governments.
Among the supporters was the British scientist William Thomson, later Lord Kelvin.
Thomson had developed in instrument called a mirror galvanometer that was sensitive enough to detect and display the weak signals that emerged from undersea cables.
Field promised investors that the company would lay the cable by the end of 1857. The plan was to load half of the cable onto each of two ships—Agamemnon and USS Niagara—and join the two lengths together while at sea.
The first attempt ended in failure.
The cable broke within a day of leaving Ireland, and there was not enough left to try again.
The manufacturers made more cable over the winter, and in 1858 Agamemnon and Niagara sailed to the middle of the Atlantic. There they joined the cables and each set off for their home shores, paying out the cable as they went.
At the second attempt, Agamemnon successfully reached Ireland on 5 August and USS Niagara arrived in Newfoundland later the same day. Everyone held their breath as engineers made the first test, but the cable worked as expected and they successfully sent and received signals both ways.
The formal exchange between the President and the Queen went ahead as planned, and journalists excitedly reported the technological feat:
The Old and New Worlds are brought into instantaneous communication.
Saturday Review (7 August, 1858)
Despite the success of laying the cable, it was far from ready to handle the traffic the business community was so eager to send. Even using Thomson’s sensitive mirror galvanometer, each letter took a painfully long time to send and receive.
When the company’s chief electrician, the British surgeon Wildman Whitehouse, tried to improve the signal by increasing the voltage, the cable’s insulation failed and it ceased to transmit.
How was the cable improved?
Field did not give up. He set up a new company in 1864, chaired by the engineer Daniel Gooch of the Great Western Railway, and raised the money to manufacture an improved cable.
The company bought Isambard Kingdom Brunel’s steamship Great Eastern, then the largest ship afloat, and converted it to lay cables.
By May 1865, 2,600 miles of new cable were ready.
The Great Eastern sailed from Ireland westwards, carrying the full length of cable.
But more than halfway through the journey, the cable snapped and was lost on the ocean floor.
When was the cable finally successful?
Undeterred, the team led by engineer Samuel Canning tried once more.
The Great Eastern set sail again on 13 July 1866, and reached Heart’s Content, Newfoundland, on 27 July. This time the cable’s insulation held out, and the transatlantic link was established.
On 9 August the steamship set sail again for the point in the Atlantic where the cable had broken the previous year, which the crew had marked with a buoy. After over two weeks of trying, at the end of August they managed to hook the end of the cable successfully and bring it aboard.
Early on Sunday 2 September they took it to the instrument room. Silence fell as the electricians attempted to call Ireland. Gooch recorded in his diary,
I think my heart ceased to beat during those few minutes.
At last an answering signal arrived from Ireland and the crew celebrated their amazing feat. The engineers spliced new cable to the end, and the Great Eastern steamed back to Heart’s Content.
What was the significance of transatlantic telegraphy?
The 1866 expedition saved the investment in the 1865 cable, as well as doubling the capacity for signal traffic across the Atlantic.
In a matter of years, long-distance submarine cables linked continents and islands—and in 1902, a telegraph cable from Canada to New Zealand completed a network that encircled the globe.
Instantaneous global communication had finally arrived.
And although technology has moved on unimaginably, the undersea cables carrying our bytes of data are laid in much the same way as the first Victorian telegraph cables.
The difference is that they can now transmit billions of words per second, allowing a speed of communication that Field, Thomson and their colleagues could only have dreamed of.