Napoleonic Telecommunications: The Chappe Semaphore Telegraph

The telegraph used by France during the Napoleonic Wars was an optical system based on the use of semaphore signals. When the Chappe semaphore telegraph was introduced during the French Revolution, it revolutionized communications by dramatically reducing the length of time it took for messages to travel. Although the semaphore telegraph was costly and could not operate at night or during bad weather, it was used for over 60 years, and paved the way for the introduction of the more efficient electrical telegraph later in the 19th century.

Chappe semaphore telegraph demonstration

A demonstration of the Chappe semaphore telegraph

Chappe’s invention

The Napoleonic telegraph system was invented by Claude Chappe. Chappe, who was born in Brûlon on December 25, 1763, initially embarked on a religious career. When he graduated from college in 1783, he became a commendatory abbot and was given two benefices near Paris. Chappe had a longstanding interest in science (his uncle, astronomer Jean-Baptiste Chappe d’Auteroche, was known for his observations of the Transit of Venus), so he used the funds to set up a laboratory in his home. He conducted physics experiments and wrote papers about the results.

With the crackdown on the church during the French Revolution, Chappe lost his benefices. He returned to Brûlon and turned to science full-time. In early 1790, he began working with his brothers on the development of a long-distance signalling system. Chappe experimented with different designs, trying methods that relied variously on electricity, sound, and smoke. He finally settled on a system in which telescopes were used to observe visual signals that could then be deciphered. Optical signalling systems dated back over two thousand years, in the form of hydraulic telegraphs (used in ancient Greece), torches and smoke signals, but had not been used on a large scale in the modern world.

On March 2, 1791, the Chappes offered the first public demonstration, sending a message between Brûlon and Parcé, some 16 kilometres (10 miles) away. The message was: “Si vous réussissez vous serez bientôt couvert de gloire [If you succeed, you will soon bask in glory].” (1)

More than glory, Chappe needed money. Fortunately, his brother Ignace was soon elected to the new Legislative Assembly in Paris. Ignace arranged for Claude to address the Assembly on March 24, 1792. Among other things, Claude pointed out how useful his system could be in sending orders to the frontiers, something that became particularly relevant when France declared war on Prussia and Austria a month later.

In September 1792, the Legislative Assembly was disbanded and replaced with the National Convention, to which Ignace did not gain election. But by then the Chappes had supporters among the legislators. On August 4, 1793, the Convention approved funds for the construction of a line of stations from Paris to Lille, some 200 km to the north, near the Austrian Netherlands. Chappe was given the title of “Telegraph Engineer” and a salary. He continued to improve on his design.

On August 15, 1794, the first official message was sent along the line to Paris, reporting the recapture of Le Quesnoy: “Austrian garrison of 3,000 slaves has laid down its arms and surrendered at discretion.” (2) The message arrived about an hour after the battle ended. A courier would have taken a further 10 hours to arrive.

In October 1794, the Convention authorized the construction of a second line, connecting Paris to Strasbourg. This was completed in May 1798. Later that year, a telegraph line opened between Paris and Brest.

How the Chappe telegraph worked

Chappe telegraph scale model

Scale model of a Chappe telegraph

Claude Chappe initially called his invention the tachygraphe (from the Greek for “fast writer”), but was persuaded to change the name to telegraph (“far writer”), a name coined by French statesman André François Miot de Mélito.

Telegraph stations were situated roughly 10 to 15 km apart, within sight of each other, either on existing high places, such as belfries, or on towers specially-constructed for the purpose. Each tower was equipped with two telescopes – one pointed toward the nearest station up the line, the other toward the nearest station down the line – and an apparatus that Chappe called a semaphore (from the Greek for “bearing a sign”). The latter consisted of two movable wooden arms (each called an indicator) connected by a long, movable wooden cross-bar (called the regulator). The arms were counterbalanced with iron weights. The regulator and indicators were painted black to increase their contrast against the sky.

The regulator could be positioned vertically or horizontally (when it was in an oblique, or diagonal, position, it was not transmitting a signal). Each indicator could be placed at one of seven angles, each 45 degrees apart (excluding the position in which an indicator was extending the regulator). This resulted in a total of 98 (2 x 7 x 7) unique positions. Six positions were reserved for control signals, leaving 92 positions for coded signals (letters of the alphabet, numbers, frequently-used syllables).

In 1795, a 92-page code book was introduced, along with a two-step signalling system. The first signal indicated the page of the code book; the second indicated the line (individual words, abbreviations, sentences, etc., numbered from 1 to 92) on that page. This meant that 8464 (92 x 92) codes could be transmitted. Later refinements eventually resulted in 40,000 codes.

Each station was staffed by two operators. A control mechanism, designed and built by clockmaker Abraham-Louis Breguet, allowed an operator to adjust the regulator and indicators from inside the building, via a scale model of the semaphore, using pulleys and ropes.

An operator moved the arms through a sequence of positions, spelling out a message in code. The operator in the next tower read the message through a telescope, and then replicated it, passing it along to the next tower. Operators had to verify that the next station was correctly reproducing each signal, thus reducing the risk of transmission errors. Coding and decoding happened only at the end station and at divisional stations (every 10th to 15th station). At the in-between stations, the operators simply repeated the signal without knowing the code. The ability to code and decode at divisional stations meant that when weather conditions obscured the line of sight, a messenger could carry the message to a divisional station that was experiencing better weather and have the message re-transmitted from there. Special signals were used to indicate the priority of the message, which was helpful in situations where there were messages travelling in opposite directions. In cases where messages had equivalent priority, those from Paris were transmitted first.

In good weather, the duration of a transmission was 20-30 seconds per symbol per station. In 1823, a newspaper reported:

News can be received at Paris in three minutes from Calais by means of thirty-three telegraphs; in two minutes from Lisle, by twenty-two telegraphs; in six minutes and an half from Strasbourg, by forty four telegraphs; in twenty minutes from Toulon by 100 telegraphs; and in eight minutes from Brest, by sixty four telegraphs. (3)

This was compared to the average speed of a mail coach of around 10 km/hour.

The telegraph under Napoleon

Claude Chappe

Claude Chappe

In 1799, Napoleon Bonaparte seized power through a coup d’état. Chappe met with Napoleon to propose commercial use of the telegraph system. He suggested using it to relay daily commodity prices and national news, but Napoleon agreed to only one civilian use: the weekly transmission of results from the state-run lottery.

Napoleon regarded the telegraph as more useful for military and administrative purposes. He ordered an extension of the network, including a line to Boulogne in preparation for his planned invasion of England. In 1801, he asked Claude Chappe’s brother Abraham to design a station capable of transmitting a signal across the English Channel. Chappe built and tested a prototype (with an extra-large semaphore) between Belleville and Saint-Martin-du-Terre, approximating the shortest distance across the Channel. A large station was installed in Boulogne, but Napoleon’s invasion never happened.

Under Napoleon, the Paris-Lille line was extended to Brussels in 1802, and to Antwerp in 1809. In 1804, Napoleon ordered the construction of a line from Paris to Milan via Lyon. Other European countries, including Sweden, Britain, Denmark and Portugal, were spurred into developing their own telegraph systems, or adopting variations of Chappe’s design.

Meanwhile, Claude Chappe was growing increasingly depressed as rivals claimed to have invented better forms of the telegraph, or to have invented it before him. Even Breguet insisted he contributed more to Chappe’s design than he was given credit for. On January 23, 1805, Chappe killed himself by jumping into a well outside the Telegraph Administration building in Paris. He was 41 years old. His tombstone, at Père Lachaise cemetery in Paris, features a lead replica of a telegraph tower with the arms positioned in the signal for “at rest.”

During the 1809 campaign, Napoleon tried to use the telegraph to command his army from a distance. He sent his Chief of Staff, Louis-Alexandre Berthier, to set up Imperial headquarters at Strasbourg. On April 10, Napoleon sent orders to Berthier telling him to go to Augsburg, and if the Austrians attacked before April 15, to concentrate the troops at Augsburg and Donauworth, make them ready to march, and send Napoleon’s guard and horses to Stuttgart. Unfortunately, the message was delayed by fog and did not reach Berthier until April 16. Napoleon was also communicating with Berthier via courier, which led to further confusion as messages would arrive out of sequence, depending on the form of transmission. Berthier finally told Napoleon that he needed to join the army in person.

In 1810, the telegraph system was extended to Venice and Amsterdam, and in 1813 to Mainz. In 1811, the telegraph was used to announce the birth of Napoleon’s son. In 1812, Napoleon asked Abraham Chappe to design a mobile telegraph he could take with him on the Russian campaign, but this proved unviable.

Unfortunately, there was no telegraph line between Paris and Toulouse, in the south of France. This meant that on April 10, 1814, four days after Napoleon abdicated the French throne, some 1,000 people were killed and over 7,000 were injured in a battle at Toulouse between French forces under Marshal Soult and a coalition of British, Spanish and Portuguese troops under the Duke of Wellington. A French colonel and an English colonel left Paris on April 7 with the news that the war was over, but they did not reach Toulouse until April 12.

The telegraph after Napoleon

Although the French telegraph lines in Italy, Belgium, Germany and Holland disappeared after Napoleon’s fall, new telegraph lines continued to be constructed until 1846. The network grew to 556 stations covering approximately 5,000 km (3,000 miles) of lines, most of them in France. Small telegraph lines were installed in the French colonies of Algeria and Morocco.

In 1846, the French government decided to replace the optical telegraph with an electric one. England had been using the electric telegraph since 1837. This did not mark the last French use of the optical telegraph, however. During the Crimean War (1853-56), specially designed mobile Chappe stations could be built in 20 minutes, faster than long-distance electric telegraph lines. The last news reportedly transmitted by a Chappe telegraph was the fall of Sebastopol in 1855.

The optical telegraph was expensive to operate, limited to government use (a French bill passed in 1837 banned private networks), unable to operate at night (attaching lanterns to the ends of the indicators did not help) or in bad weather (fog, rain, snow), and susceptible to operator misbehavior. In 1836, some telegraph operators were found to have been introducing a specific pattern of errors into messages, to relay information about the stock market to Bordeaux. Nonetheless, the Chappe telegraph was a revolution in communications at the time, and paved the way for future developments by proving that simple signs could be used to rapidly send complex messages over long distances.

In Alexandre Dumas’ novel, The Count of Monte Cristo, the count says:

Yes, a telegraph! I had often seen one placed at the end of a road on a hillock, and in the light of the sun its black arms, bending in every direction, always reminded one of the claws of an immense beetle; and I assure you it was never without emotion that I gazed on it, for I could not help thinking how wonderful it was that these various signs should be made to cleave the air with such precision as to convey to the distance of some 300 leagues the ideas and wishes of a man sitting at a table at one end of the line to another man similarly placed at the opposite extremity, and all this effected by the simple act of volition on the part of the individual communicating the intelligence. I began to think of genii, sylphs, gnomes, in short, of all the ministers of the occult sciences until I laughed aloud at the freaks of my own imagination. Now, it never occurred to me to wish for a nearer inspection of these large insects with their long black claws, for I always feared to find under their stone wings some little human genius fagged to death with cabals, factions, and government intrigues. But one fine day I learned that the mover of this telegraph was only a poor wretch hired for 1200 francs a year, and employed all the day, not in studying the heavens like an astronomer, nor in gazing on the water like an angler, nor even enjoying the privilege of observing the country around him; but all his monotonous life was passed in watching his fellow-insect, who was placed four or five leagues distant from him. (4)

The telegraph is how news of Napoleon’s (fictional) escape from St. Helena reaches Paris in Napoleon in America.

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  1. Ignace Chappe, Histoire de la télégraphie (Paris, 1824), p. 239.
  2. C.B. Rogers, Napoleon’s Army (Barnsley, South Yorkshire, 2005), p. 90.
  3. Niles Weekly Register (Baltimore, MD), May 17, 1823.
  4. Alexandre Dumas, The Count of Monte Cristo, Vol. II (London, 1846), p. 55.

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I had often seen one placed at the end of a road on a hillock, and in the light of the sun its black arms, bending in every direction, always reminded one of the claws of an immense beetle.

Alexandre Dumas