The electric telegraph

In 1831 Joseph Henry rang a bell over a mile of copper wire for his classes at the Albany Academy. In 1832 he relayed messages from his laboratory to his home.

Samuel Morse was once a portrait painter who turned to inventing. His interest in the telegraph began in 1832, and he demonstrated his equipment in 1837.

In February 1838 Morse gave Congress its first public demonstration of the telegraph.

Morse's US patent No. 1,647 for the telegraph dates from 1840.

After about five years of searching for money, Morse was granted $30,000 by Congress for a trial line between Washington, DC, and Baltimore, Maryland.

On 24 May 1844 Morse tapped out 'What hath God wrought' from the Supreme Court Chamber in the Capitol to his partner Alfred Vail in Baltimore.

By about 1861 telegraph lines stretched from coast to coast, mostly alongside railways, and the first transcontinental line was built that year.

Alfred Vail, Morse's assistant, redesigned Morse code around 1840. His version proved more reliable than rival systems and came to dominate telegraphy.

The code uses dots, dashes and spaces. A dash lasts about as long as three dots, and the length of a space shows whether the next signal belongs to the same symbol or starts a new one.

Electrical switches produced the dots and dashes, much as a computer uses ones and zeros. Receivers turned the pulses into sound, and messages were sometimes recorded on paper tape.

An experienced operator could send about 20 words a minute with a telegraph key.

Morse code stayed in use for military and long-distance radio until the 1990s.

Before the cable, no message could travel faster than the fastest steamships, which needed at least 10 days to cross between America and Europe.

By 1858 many shorter submarine cables already worked in gulfs, harbours and lakes. The Atlantic cable was unusual mainly for its length.

An attempt in August 1857 failed when the cable snapped after about 400 miles.

In 1858 the cable ships reached port on 4 and 5 August, and the line was officially opened on 16 August. It failed within a few weeks of opening.

Queen Victoria's 98-word message to President Buchanan, congratulating him on the cable's completion, took about 16 hours to send.

In 1866 the Great Eastern left Valentia, Ireland, on 13 July and landed the cable at Heart's Content, Newfoundland, on 27 July. By 8 September 1866 two lines were operating.

Western Union was formed in April 1856 to use the telegraph for cross-country messages that arrived in under a day.

Telegrams were most popular in the 1920s and 1930s, when sending one cost less than a long-distance phone call. Senders wrote 'stop' instead of a full stop because punctuation cost extra.

By 2005 only about 20,000 telegrams were sent, at roughly $10 each.

Effective 27 January 2006, Western Union discontinued all telegram and commercial messaging services. India's state-run telegram service lasted until 2013.