Optical telegraphy

This article is about the communication system using towers with pivoting shutters. For the now closed railway in Adelaide, Australia, see Semaphore railway line. For other uses, see Semaphore (disambiguation).


A semaphore telegraph, optical telegraph, shutter telegraph chain, Chappe telegraph, or Napoleonic semaphore is a system of conveying information by means of visual signals, using towers with pivoting shutters, also known as blades or paddles. Information is encoded by the position of the mechanical elements; it is read when the shutter is in a fixed position.

The system was invented in 1792 in France by Claude Chappe, and was popular in the late 18th to early 19th century.[1][2][3]

Semaphore lines were a precursor of the electrical telegraph. They were far faster than post riders for bringing a message over long distances, but far more expensive and less private than the electrical telegraph lines which would replace them. The distance that an optical telegraph can bridge is limited by geography and weather; thus, in practical use, most optical telegraphs used lines of relay stations to bridge longer distances.

Modern derivatives of the semaphore system include flag semaphore (a flag relay system) and the heliograph (optical telegraphy using mirror-directed sunlight reflections).

Etymology

The word semaphore was coined in 1801 by the French inventor of the Semaphore line, Claude Chappe, who also coined the word "telegraph".[4]

The word "semaphoric" was first printed in English in 1808: "The newly constructed Semaphoric telegraphs" referring to the destruction of telegraphs in France.[5] The word semaphore was first printed in English in 1816: "The improved Semaphore has been erected on the top of the Admiralty", referring to the installation of a simpler telegraph invented by Sir Home Popham. The word was derived from "sémaphore", coined in French from Greek σῆμα (sêma, "sign") and φωρος (phoros, "bearer").[6]

History


Optical telegraphy dates from ancient times, in the form of hydraulic telegraphs, torches (as used by ancient cultures since the discovery of fire) and smoke signals.

Modern design of semaphores was first foreseen by the British polymath Robert Hooke, who first gave a vivid and comprehensive outline of visual telegraphy to the Royal Society in an 1684 submission in which he outlined many practical details. The system (which was motivated by military concerns, following the recent Battle of Vienna in 1683) was never put into practice.[7][8]

The first achieved optical telegraph arrived in 1792 from the French engineer Claude Chappe and his brothers, who succeeded in covering France with a network of 556 stations stretching a total distance of 4,800 kilometres (3,000 mi). Le systeme Chappe was used for military and national communications until the 1850s.

Many national services adopted signaling systems different from the Chappe system. For example, the UK and Sweden adopted systems of shuttered panels (in contradiction to the Chappe brothers' contention that angled rods are more visible). In Spain, the engineer Agustín de Betancourt developed his own system which was adopted by that state. This system was considered by many experts in Europe better than Chappe's, even in France.

France


During 1790–1795, at the height of the French Revolution, France needed a swift and reliable communication system to thwart the war efforts of its enemies. France was surrounded by the forces of Britain, the Netherlands, Prussia, Austria, and Spain, the cities of Marseille and Lyon were in revolt, and the British Fleet held Toulon. The only advantage France held was the lack of cooperation between the allied forces due to their inadequate lines of communication.

In the summer of 1790, the Chappe brothers set about devising a system of communication that would allow the central government to receive intelligence and to transmit orders in the shortest possible time. On 2 March 1791 at 11am, they sent the message “si vous réussissez, vous serez bientôt couverts de gloire” (If you succeed, you will soon bask in glory) between Brulon and Parce, a distance of 16 kilometres (9.9 mi). The first means used a combination of black and white panels, clocks, telescopes, and codebooks to send their message.

The Chappes carried out experiments during the next two years, and on two occasions their apparatus at Place de l'Étoile, Paris was destroyed by mobs who thought they were communicating with royalist forces. However in the summer of 1792 Claude was appointed Ingénieur-Télégraphiste and charged with establishing a line of stations between Paris and Lille, a distance of 230 kilometres (about 143 miles). It was used to carry dispatches for the war between France and Austria. In 1794, it brought news of a French capture of Condé-sur-l'Escaut from the Austrians less than an hour after it occurred.[9] The first symbol of a message to Lille would pass through 15 stations in only nine minutes. The speed of the line varied with the weather, but the line to Lille typically transferred 36 symbols, a complete message, in about 32 minutes.

Paris to Strasbourg with 50 stations was the next line and others followed soon after. By 1824, the Chappe brothers were promoting the semaphore lines for commercial use, especially to transmit the costs of commodities. Napoleon Bonaparte saw the military advantage in being able to transmit information between locations, and carried a portable semaphore with his headquarters. This allowed him to coordinate forces and logistics over longer distances than any other army of his time. However because stations had to be within sight of each other, and because the efficient operation of the network required well trained and disciplined operators, the costs of administration and wages were a continuous source of financial difficulties. Only when the system was funded by the proceeds of its own lottery did costs come under control.


In 1821 Norwich Duff, a young British Naval officer, visiting Clermont-en-Argonne, walked up to the telegraph station there and engaged the signalman in conversation. Here is his note of the man's information:

The pay is twenty five sous per day and he [the signalman] is obliged to be there from day light till dark, at present from half past three till half past eight; there are only two of them and for every minute a signal is left without being answered they pay five sous: this is a part of the branch which communicates with Strasburg and a message arrives there from Paris in six minutes it is here in four.

Description


The Chappe brothers determined by experiment that it was easier to see the angle of a rod than to see the presence or absence of a panel. Their semaphore was composed of black movable wooden arms, the position of which indicated alphabetic letters. With counterweights (named forks) on the arms, the Chappe system was controlled by only two handles and was mechanically simple and reasonably robust. Each of the two 2-metre-long arms showed seven positions, and the 4.6-metre-long cross bar connecting the two arms had four different angles, for a total of 196 symbols (7x7x4). Night operation with lamps on the arms was unsuccessful.

To speed up transmission and to provide some semblance of security a code book was developed for use with semaphore lines. The Chappes' corporation used a code that took 92 of the basic symbols two at a time to yield 8,464 coded words and phrases.

From 1803 on, the French also used the 3-arm Depillon semaphore at coastal locations to provide warning of British incursions.[1]

Sweden


At the same time as Chappe, the Swedish inventor Abraham Niclas Edelcrantz experimented with the optical telegraph in Sweden. In 1794 he inaugurated his telegraph with a poem dedicated to the Swedish King on his birthday. The message went from the Palace in Stockholm to the King at Drottningholm.

Edelcrantz eventually developed his own system which was quite different from its French counterpart and nearly twice as fast. The system was based on ten collapsible iron shutters. The various positions of the shutters formed combinations of numbers which were translated into letters, words or phrases via codebooks. The telegraph network consisted of telegraph stations positioned at about 10 kilometres (6.2 mi) from one another.

Soon telegraph circuits linking castles and fortresses in the neighbourhood of Stockholm were set up and the system was extended to Grisslehamn and Åland. Subsequently telegraph circuits were introduced between Gothenburg and Marstrand, at Helsingborg and between Karlskrona and its fortresses. Sweden was the second country in the world, after France, to introduce an optical telegraph network. The Swedish optical telegraph network was restricted to the archipelagoes of Stockholm, Gothenburg and Karlskrona. Like its French counterpart, it was mainly used for military purposes.

U.K.


Lord George Murray, stimulated by reports of the Chappe semaphore, proposed a system of visual telegraphy to the British Admiralty in 1795.[3] He employed rectangular framework towers with six, five feet high octagonal shutters on horizontal axes that flipped between horizontal and vertical positions to signal. [10] The Rev. Mr Gamble also proposed two distinct five element systems in 1795: one using five shutters, and one using five ten foot poles.[3] The British Admiralty accepted Murray's system in September 1795, and the first system was the 15 site chain from London to Deal.[11] Messages passed from London to Deal in about sixty seconds, and sixty-five sites were in use by 1808.[11]

Chains of Murray's shutter telegraph stations were built along these routes:

Liverpool—Holyhead

Liverpool, Bidston, Hilbre Island, Voel Nant, Foryd, Llysfaen, Puffin Island, Point Lynas, Carreglwyd, Cefn Du, Holyhead[12]

London—Deal and Sheerness

Admiralty (London), West Square Southwark, New Cross, Shooter's Hill, Swanscombe, Gad's Hill, Callum Hill, Beacon Hill (Faversham, branch point), Shottenden, Barham Downs, Betteshanger, Deal.

(branch) Beacon Hill (Faversham), Tonge, Barrow Hill, Sheerness.

London—Great Yarmouth

Admiralty (London), Hampstead Heath (Telegraph Hill), Woodcock Hill, St Albans, Dunstable Downs, Lilley Hoo, Baldock, Royston, Gog Magog Hills, Newmarket (Side Hill), Icklingham, Barnham, East Harling, Carleton Rode, Wreningham, Norwich, Strumpshaw, Great Yarmouth.

London—Portsmouth and Plymouth

Admiralty (London), Chelsea Royal Hospital, Putney Heath, Cabbage Hill, Netley Heath, Hascombe, Blackdown, Beacon Hill (branch point), Portsdown Hill, Portsmouth (Southsea Common).

(branch) Beacon Hill, Chalton, Wickham, Town Hill, Toot Hill, Bramshaw, Pistle Down, Chalbury, Blandford racecourse, Belchalwell, Nettlecombe Tout, High Stoy, Toller Down, Lamberts Castle, Dalwood Common, St Cyrus, Rockbeare, Gt Haldon, South Knighton, Marley, Lee, Saltram, Plymouth.

The shutter stations were temporary wooden huts, and at the conclusion of the Napoleonic wars they were no longer necessary, and were closed down by the Admiralty in March 1816.[13]

A replacement system was sought, and of the many ideas and devices put forward the Admiralty chose the simpler semaphore system invented by Sir Home Popham.[2][3] A Popham semaphore was a single fixed vertical 30 foot pole, with two movable 8 foot arms attached to the pole by horizontal pivots at their ends, one arm at the top of the pole, and the other arm at the middle of the pole.[1][2] The signals of the Popham semaphore were found to be much more visible than those of the Murray semaphore.[1] Popham's 2-arm semaphore was modeled after the 3-arm Depillon French semaphore.[1] An experimental semaphore line between the Admiralty and Chatham was installed in July 1816, and its success helped to confirm the choice.[13]

Subsequently the Admiralty decided to establish a permanent link to Portsmouth and built a chain of semaphore stations. Work started in December 1820[13] and the line was operational from 1822 until 1847, when the railway and electric telegraph provided a better means of communication. The semaphore line did not use the same locations as the shutter chain, but followed almost the same route with 15 stations:

Admiralty (London), Chelsea Royal Hospital, Putney Heath, Coombe Warren, Coopers Hill, Chatley Heath, Pewley Hill, Bannicle Hill, Haste Hill (Haslemere), Holder Hill, (Midhurst), Beacon Hill, Compton Down, Camp Down, Lumps Fort (Southsea) and Portsmouth Dockyard. The semaphore tower at Chatley Heath, which replaced the Netley Heath station of the shutter telegraph, has been restored by Surrey County Council and is open to the public.

A semaphore-based successor for the London to Plymouth shutter telegraph chain, branching much closer to London, at Chatley Heath in Surrey, was started but abandoned before completion.

Many of the prominences on which the towers were built are known as 'Telegraph Hill' to this day. As in France the network required lavish amounts of money and manpower to operate and could only be justified as a defence need.

Other countries


Once it had proved its success, the optical telegraph was imitated in many other countries, especially after it was used by Napoleon to coordinate his empire and army. In most of these countries, the postal authorities operated the semaphore lines.

In Portugal, the British forces fighting Napoleon in Portugal soon found that the Portuguese Army had already a very capable semaphore terrestrial system working since 1806, giving the Duke of Wellington a decisive advantage in intelligence. The innovative Portuguese telegraphs, designed by Francisco Ciera, a mathematician, were of 3 types: 3 shutters, 3 balloons and 1 pointer/moveable arm (the first for longer distances, the other two for short) and with the advantage of all having only 6 significant positions. He also wrote the code book "Táboas Telegráphicas", with 6.666 entrances (1 to 6, 11 to 16,... 61 to 66, 111 to 116,... etc.), the same for the 3 systems. Since early 1810 the network was operated by "Corpo Telegráfico", the first Portuguese military Signal Corps.

In Canada, Prince Edward, Duke of Kent established the first semaphore line in North America. In operation by 1800, it ran between the city of Halifax and the town of Annapolis in Nova Scotia, and across the Bay of Fundy to Saint John and Fredericton in New Brunswick. In addition to providing information on approaching ships, the Duke used the system to relay military commands, especially as they related to troop discipline. The Duke had envisioned the line reaching as far as the British garrison at Quebec City. However, the many hills and coastal fog meant the towers needed to be placed relatively close together to ensure visibility. The required labour to build and continually man so many stations taxed the already stretched-thin British military and there is doubt the New Brunswick line was ever in operation. With the exception of the towers around Halifax harbour, the system was abandoned shortly after the Duke's departure in August 1800.[14][15]


In 1801, the Danish post office installed a semaphore line across the Great Belt strait, Storebæltstelegrafen, between islands Funen and Zealand with stations at Nyborg on Funen, on the small island Sprogø in the middle of the strait, and at Korsør on Zealand. It was in use until 1865.[16]

The Kingdom of Prussia began with a line 750 kilometres (470 mi) long between Berlin and Coblenz in 1833, and in Russia, Tsar Nicolas I inaugurated a line between Moscow and Warsaw of 1,200 kilometres (750 mi) length in 1833; it needed 220 stations manned by 1,320 operators.

In the United States the first optical telegraph was built by Jonathan Grout. It was a 104 kilometres (65 mi) line connecting Martha's Vineyard with Boston, and its purpose was to transmit news about shipping. One of the principal hills in San Francisco, California is also named "Telegraph Hill", after the semaphore telegraph which was established there in 1849 to signal the arrival of ships into San Francisco Bay.

The semaphores were successful enough that Samuel Morse failed to sell the electrical telegraph to the French government. However, France finally committed to replace semaphores with electric telegraphs in 1846. Note that electric telegraphs are both more private and almost completely unaffected by weather; they also work at night. Many contemporaries predicted the failure of electric telegraphs because "they are so easy to cut."[17] The last stationary semaphore link in regular service was in Sweden, connecting an island with a mainland telegraph line. It went out of service in 1880.


In Ireland, Richard Lovell Edgeworth (1744–1817) proposed a telegraph there when a French invasion was anticipated in 1794, and again in 1796; however, the proposal was not implemented.

The Chappe telegraph in the literature

  • In "Mister Pencil" (1831), comic strip by Rodolphe Töpffer, a dog fallen on a Chappe telegraph's arm and its master attempting to help provoke an international crisis by involuntarily transmitting disturbing messages.
  • In "Lucien Leuwen" (1834), Stendhal pictures a power struggle between Lucien Leuwen and the prefect M. de Séranville with the telegraph's director M. Lamorte.
  • In Chapter 60 ("The Telegraph") of Alexandre Dumas' The Count of Monte Cristo (1844), the title character describes with fascination the semaphore line's moving arms. "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 me of the claws of an immense beetle..." He later bribes a semaphore operator to relay a false message in order to manipulate the French financial market. Dumas also describes in details the functioning of a Chappe telegraph line.
  • In the Hector Malot's novel Romain Kalbris (1869), one of the characters—a girl named Dielette, describes her home in Paris as "...next to a church near which there was a clock tower. On top of the tower there were two large black arms, moving all day this way and that. [I was told later] that this was Saint-Eustache church and that these large black arms were a telegraph."
  • In chapter 10 of C. S. Forester's Hornblower and the Hotspur (1962), the destruction of a French semaphore tower and a shore battery is a key plot point. A similar event is also the focus of the seventh episode of the A&E Horatio Hornblower series.
  • In the young adult fiction book Death Cloud by Andy Lane (2010), Mycroft Holmes tells 14-year-old Sherlock Holmes about semaphore stations, commenting about his school beforehand, saying "All the Latin a boy can cram into his skull, but nothing of practical use."

Fictional semaphores in the literature

  • In the alternative history novel, Lest Darkness Fall (1939), by L. Sprague de Camp, the protagonist, a 20th Century man who falls into Dark Age Rome, develops a semaphore system to warn of invasion. To make it practical he also invents the telescope.
  • Pavane (1968), an alternate history novel by Keith Roberts, features a society where long distance communication is by a network of semaphores operated by the powerful Guild of Signallers.
  • Terry Pratchett's Discworld novels (1983) describe a system of 8-shutter semaphore towers, known as Clacks. In the alternate universe of the Discworld, the semaphore system occupies a similar role to that of the Internet on Roundworld. Using advanced clacks coding it is possible not only to send very fast telegrams, but also to encode pictures and send them long-distance. Shopping and banking via the clacks is also mentioned, in a similar fashion to online shopping.
  • In David Weber's Safehold series (2007), a world-wide Semaphore system is used by the Church to help them maintain their dominion over the world.
  • In Alastair Reynolds' Terminal World (2010), the distant-future terrain is criss-crossed with semaphore lines relaying information between the one remaining city, Spearpoint, outlying communities and the airborne community Swarm.

See also

References

Citations
Bibliography
  • Crowley, David and Heyer, Paul (ed) (2003) 'Chapter 17: The optical telegraph' Communication in History: Technology, Culture and Society (Fourth Edition) Allyn and Bacon, Boston pp. 123–125

Further reading

  • The Old Telegraphs, Geoffrey Wilson, Phillimore & Co Ltd 1976 ISBN 0-900592-79-6
  • Faster Than The Wind, The Liverpool to Holyhead Telegraph, Frank Large, an avid publication ISBN 0-9521020-9-9
  • The early history of data networks, Gerard Holzmann and Bjorn Pehrson, Wiley Publ., 2003, ISBN 0-8186-6782-6
  • Semaphore Signaling, Chapter 2 of: Communications: an international history of the formative years, R.W. Burns, Institution of Electrical Engineers, 2004 ISBN 978-0-86341-327-8

External links

  • Chappe's semaphore (an illustrated history of optical telegraphy)
  • Webpage including a map of England's telegraph chains
  • Diagrams and maps of Murray's U.K. semaphore stations
  • Photo and diagrams of Popham's U.K. semaphore stations
  • Map of visual telegraph (semaphore) and electrical telegraph lines in Italy, 1860 (in Italian)
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.