Sunday, November 25, 2007

Semaphore as Information Network

Claude Chappe had tried it out with his brothers and believed - no, knew it could work. He had a vision of quick national communication - much faster than a messenger could ride, much more communicative than a signal fire.

Messengers and signal fires had been around for thousands of years, and had served armies and governments relatively well. With the re-invention of the telescope in the early 1600s (and it subsequent popularity for naval and astronomical observation), technology had changed, allowing for more freedom of the seas and the land. By the late 1700s, the atmosphere of Europe was rife with invention, and people began to look to every technology and how it could be used for new (or old) applications.

Claude Chappe, who came from a well-to-do family and who had been an abbe with a secure income, had always been interested in physics, particularly optics. His uncle Abbé Jean Baptiste Chappe d'Auteroche (1722-1769), who was also in the clergy, as well as being a famous cartographer and astronomer, had traveled to Siberia in 1761 to observe the passage of Venus in front of the sun and published a well-known book about it, Voyage en Siberie. This same uncle had died of yellow fever in California while there to observe another celestial event. A eulogy was held in Paris to honor him, and his westerly observations were published posthumously.

Claude was well on his way to following in his uncle's footsteps, but the French Revolution intervened, and he and all his brothers were left unemployed. Despite the atmosphere of paranoia, where people were being beheaded for slight deviations in behavior, Claude decided to pursue an idea that had been put about, both as a reasonable scheme and as various harebrained ones: the idea of a telegraph, where signals would be passed along a line of stations, each one manned by someone trained to read the signal and reproduce it for the next station. After a few experiments, Claude came to the correct conclusion that the telegraph system should be optical - using telescopes to read the signals - because the distance between stations could then be lengthened quite a bit.

Here is an account of someone else who had experienced good results with an optical telegraph:

"One of the more practical proposals came from De Courrejolles, a captain in the French navy.[Note 12] In February 1783, De Courrejolles was engaged in battle with the English fleet, at what is described as the Turkish or Ionic Isles...He found himself surrounded by an English squadron commanded by Admiral Hood. De Courrejolles had a simple optical telegraph erected at a mountain top on the coast of one of the islands, and used it to monitor the enemy's movements. Every change in position was reported by the telegraph. Using this information De Courrejolles was able to overrun a squadron commanded by the then Captain (later Admiral) Nelson, and force the English fleet to retreat. Inspired by this success, De Courrejolles submitted a proposal to the French Minister of War to have the army adopt optical telegraphs for signaling purposes. Though De Courrejolles was unsuccessful at that time, he may well have paved the way for Chappe."

At a symposium in Sweden on the optical telegraph in 2004, a history of the Chappe network was presented in beautiful, researched detail. Unfortunately, this seems to have been taken down, but I found it via the Wayback Machine, and you can read it for yourself, if you like. Here's a quote about Claude casting about for methods to make his dream succeed:

"Abraham Chappe later wrote that Claude performed many experiments to find a good alternative, including the use of electrical signals traveling through conducting wires. He records that an optical method was only chosen. . . after having tried, unsuccessfully, electricity, various acoustical methods, the use of smoke produced by different types of combustible materials, etc. The idea to use an electrical signal had to be abandoned when no adequate insulators could be found for the wires."

So close! There were numbers of people thinking about electricity for telegraphic communication in those days, including one man in Spain who tried electrical sparks to illuminate tin-foil letters; but none of them were quite able to make it happen.

Chappe experimented and eventually adopted a design using weighted arms, which swiveled to create a large array of shapes, in effect a semaphore. Ignace is noted as saying, "Some time later [we] established with certainty that elongated objects were better visible than the sliding panels adopted before." It's interesting to note that semaphore was not used in the way we know it now, i.e., a flag-waving activity used to communicate between ships or between ships and shore, until the early 1800s.

By 1793, despite the beheading of Louis XVI and the beginning of the reign of terror, and despite the destruction of two of his signal towers by mobs who thought he was communicating with Royalist forces, Claude and his brothers had set up a telegraph line which ran between two locations near Paris, approximately 26 km apart. Having several allies within the new government, they received permission to test the line. The messages took approximately 10 minutes to transmit, an unheard-of speed at that time - and government people were there to see it happen.

This caused such excitement that within two weeks a decision had been made to establish a national telegraph system, and Claude Chappe was named Ingénieur Télégraphe (Telegraph Engineer), working for the government. Money was appropriated for the construction of a line of fifteen stations from Paris to Lille, at the frontier with the Austrian Empire; this line, when it was complete, could transmit a message in a little over half an hour, a key tool in the war between France and the Empire, as it meant the Capital could keep up on events as they happened.

If you look at this point in time, France was in a tricky position:

"France was surrounded by the allied forces of England, The Netherlands, Prussia, Austria, and Spain. The cities of Marseilles and Lyon were in revolt, and the English Fleet held Toulon. In this situation the only advantage France held was the lack of cooperation between the allied forces due to their inadequate lines of communications."[wiki]

As a result, with the success of the Lille line, optical telegraph lines were built over the entirety of France over the next twenty years or so. Napoleon loved the system, having his own portable station built which he carried with him on campaign. He also poured money into building more of the network. It wasn't cheap, because each station had to be manned by a highly-trained person, who observed the signal from other towers and knew how to pass it on. But the French system of fast communication was one of the key ingredients in France's success during the Napoleonic War, and so they hung onto it as long as they could. Claude Chappe himself remained in his position as the head of the system for over 30 years, until there was an administration change.

The Optical Telegraph system at its height covered most of the borders

By that time, however, people were finally starting to take the electric telegraph more seriously, and by 1844 America had begun work on a system of electric telegraphs which ultimately outmoded the semaphore system.

Even today you can find the towers with semaphore arms scattered all across France, sometimes with their arms drooping or missing. Some of the stations are still in working order, and you can go see them operated. It's one of those examples of a liminal moment, a place between two eras. I love things like that, things that changed the face of, say, communication while using only peoples' eyes and ears for the new technology rather than looking so far as circuits and fuses; and yet, ultimately, these systems become abandoned relatively quickly because, ultimately, someone is bound to work out the circuits and fuses...leaving behind artifacts and traces of something we couldn't possibly imagine for ourselves.


A site all about semaphores

A History of Information Highways and Byways, from NYU

Wikipedia's interesting page on the Chasqui, a network of Inca messengers who made for fast communication all over the Inca Empire.

Source for my images.


Kat said...

Ben Rubin - San Jose Semaphore

Anonymous said...

My god, it's the clacks! Terry Pratchett must have known about this before he added the semaphore network to Discworld.

Ed Lamb said...

Terry Pratchett, in his Discworld novel _Going Postal_, describes a continent-spanning semaphore system very much like the one France set up in the Napoleanic era. In the novel, the system is called "the clacks."

Some details here:

Ed Lamb said...

Oops. Here's a better link:

D said...

Love these images, very iconic shapes. The map is interesting, also the mobile semaphore...of course Napoleon put it to good use.

(Them Pratchettian clacks starts several books earlier in the series - my fav chewing-gum-for-the-brain.)

Agree that it's interesting with in-between tech. Have you read Neal Stephenson? Either Cryptonomicon or that (rather far too long) trilogy starting with Quicksilver. The former deals with analogue turning into digital (among other things) and the latter about natural science emerging from alchemy (again, along with a ton of other themes, these four books are very well written). Not too much obviously about anachronisms but very much about things changing. Fun reads. I'd love if he'd start digging into early use of steam power or electricity.

Heather McDougal said...

I have been much intimidated by Neal Stephenson's later work, but I do love Quicksilver (haven't got to the rest of the trilogy yet; my life is not slow-paced enough). The descriptions of the Royal Society, and Hook's horrific experiments, and Newton's weird brilliance, are marvelous.

Anonymous said...

A little known novel from around 1840 or so, by the great French writer Stendhal, Lucien Lieuwen refers extensively to the semaphore system (called the "telegraph" system) and reflects on the possible impact of rapid communications technology on politics. In the last section of the book, the young protagonist, sent out from Paris on a political mission by the government, uses the semaphore system to try to get his bosses to make a shift in electoral strategy in response to local conditions before it's too late. His messages get through but are ignored.