Great Wall smoke signals could warn of armies but never spell a word
Chinese signallers on the Great Wall threw wolf dung onto fires to make dark smoke by day, and by the Tang dynasty a warning could travel 1,100 kilometres in a single day. Impressive, but it was not a telegraph in the strict sense. Every signal meant something agreed in advance; nobody could send a new sentence.
That distinction is the heart of telegraphy: sending arbitrary text over long distances using a code both ends understand, rather than carrying a physical note. Flag semaphore qualifies; a pigeon with a letter does not. Ancient systems, however elaborate, fell short. Chinese flags of different colours could indicate how strong an enemy force was, yet the menu of messages stayed fixed. In the fourth century BC Aeneas Tacticus proposed matching water pots at two stations, drained in step after a torch signal, with a floating scale showing which preset message was meant.
One ancient idea did pass the test. The Greek historian Polybius suggested arranging the alphabet in a grid and raising two groups of torches, the number in each giving the letter's row and column. Nobody knows for sure whether it was ever used, though some scholars read a passage of Livy as describing it in 207 BC. After that, little comparable appeared until 1616, when Franz Kessler described a lamp in a barrel with a moving shutter, read from afar with the new telescope.
The first true telegraph in wide service was Claude Chappe's optical system of towers with movable arms, which ran from Paris to Lille and carried news of a French victory over the Austrians in 1794 less than an hour after it happened. Chappe coined both telegraph and semaphore. Such lines depended on clear weather and daylight and could pass only about two words a minute.
Electricity was slow to win official favour. In 1816 an inventor named Ronalds offered the British Admiralty a working electric telegraph and was told it was unnecessary, since the optical line to Portsmouth seemed good enough. The Morse system later became the international standard in 1865, and the telegraph declined from 1920 once telephones removed its speed advantage.
Source: Telegraphy
