If you were to glance up from the foot of the hill of 19th century Montmartre, you might notice that the the windmills weren’t the only things that once danced across the sky. Perched high on its summit stood another wooden structure, a silent sentinel of pulleys and gears. From a distance, its arms seemed to wave erratically, like an automaton testing its joints against the wind. Long before electrical wires and digital signals, these curious contraptions formed part of a state-of-the-art optical telegraph system, beaming coded messages from well-placed towers on the roof of the Louvre palace to Parisian hilltops and beyond, crossing the country at speeds unimaginable to the horse-drawn couriers trudging the muddy roads below. A crucial node in one of Europe’s most audacious communication networks, the optical telegraph is little more than a historical footnote today, yet their influence can still be felt in the modern world of instant messaging and global connectivity.
Long before the wry hum of telegraph wires or the staccato clang of Morse keys, a Frenchman named Claude Chappe and his brothers conjured a system that could outpace any rider on horseback. They called it the sémaphore, from the ancient Greek words for “sign” and “to carry.” This was the high-speed Internet of its day, if an Internet were constructed from hewn wooden arms instead of silicon chips, and reliant not on Wi-Fi or satellites but on clear skies and sharp-eyed operators.
Chappe’s optical telegraph was a hushed miracle of mechanical choreography. Looking almost like a modern transmission tower (you might even call them an eyesore), each tall tower carried a mast crowned with two large articulated arms and a central crossbar. The arms could be positioned in different angles — like some eerie marionette raised against the horizon — each corresponding to a coded letter, number, or word.
Stations were spaced anywhere from five to ten miles apart, always in line of sight, so that a semaphore signal from one station could be read through a telescope at the next. The operator there would faithfully replicate the position of the arms on his own tower, relaying the message down the line, station by station.
With a handful of well-placed towers, a message could sprint from Paris to Lille—over a hundred miles—in a fraction of the time a messenger would need on horseback. By 1794, the French Revolutionary government proudly received battlefield reports in just hours instead of days. Napoleon, ever the opportunist, expanded this “mechanical Internet,” building a vast web of nearly five hundred semaphore towers stretching throughout France and beyond. For a moment in history, the future seemed to hang on these rotating arms.
Today, of course, it’s easy to dismiss the optical telegraph as a quaint anachronism—something more at home in an H.G. Wells fantasy than in the bustle of modern Paris. But it’s worth remembering how radical the idea was in its own time. Optical telegraphs had many features now commonplace in modern networks, such as:
- control characters (extra symbols that are not part of the message itself, but still convey useful information such as a character signalling “end of message”)
- routing (choosing a path for how to send a message)
- error control (correcting errors made during transmission)
- flow control (limiting how quickly a message is sent so the recipient can keep up)
- message priority (symbols or notifiers that indicate a more important message should be sent first)
- symbol rate control (standard pace for how many letters/symbols are sent at a time).
This was a communication revolution without electricity. Speed, once the Achilles heel of all distant communication, became not only feasible but expected. You might question how a wooden apparatus on a roof could possibly have shifted the fate of nations, yet the Chappe telegraph heralded a shift in our collective mindset: suddenly, decisions could be made swiftly based on near real-time information, tightening the rhythms of governance, finance, and warfare.
Chappe tried to bring his invention mainstream, by proposing it for industry use, as well as in the financial sector, and for newspapers, but the the government only approved one proposal – the transmission of results from the state-run lottery (the lottery had been abused for years by fraudsters who knew the results, selling tickets in provincial towns after the announcement in Paris, but before the news had reached those towns). The optical telegraph made waves in several countries however, Sweden being the second country after France to it, and later, the British Empire caught on, with semaphore towers popping up in Canada and India, as well as the Prussian Empire.
Each station required alert operators with keen eyesight, trained to distinguish fine angles of arms at a distance through a telescope. So many variables—weather, daylight hours, architectural obstructions, or even a well-placed tree—could block a message. And since there was no universal dictionary of codes, operators needed large reference books filled with each signal’s meaning.
If you visit the Musée des Arts et Métiers in the Marais, you’ll find a small exhibit dedicated to the Chappe telegraph featuring a scale model of one of those semaphore towers: a slender wooden frame with articulated arms, easily as tall as a two-story house. Though the real towers were all but dismantled by the late 19th century, if you’re sharp-eyed and a bit lucky, Paris still offers a few modest hints of its forgotten telegraph era.
In Montmartre, where one prominent station once stood, holds a small plaque near the Musée de Montmartre commemorating the telegraph’s presence. It’s not much more than a marker — just enough to prompt a fleeting reflection on how this hill once carried urgent dispatches across the wind.
At the bottom of the butte, near Sacré-Cœur, you’ll find Rue Chappe, named for the brilliant inventor himself. It’s a small, cobbled street that reveals how casually Paris can nod at its history — honoring an essential figure in the global trajectory of communication with a single road sign. Elsewhere, drifting through the 6th arrondissement, you might note rooftops that, in another century, could have held semaphore arms. Some older structures such as the famous Saint-Sulpice church and the Palais du Louvre housed telegraph stations on their roofs.
By the mid-19th century, however, the optical telegraph was overshadowed by the electric telegraph, which could be used at any hour and in all weather conditions, so long as the lines held up. The mechanical arms were dismantled and forgotten, relegated to dusty references in arcane libraries. The ephemeral illusions of speed conjured by semaphore soon paled in comparison to the crackle of wires stretching across nations—and, eventually, oceans.
Yet the principle behind Chappe’s invention—the encoding, transmission, and decoding of messages over distance—remains embedded in the digital networks that now define our era. The semaphore arms may be gone, but their echoes remain in every conversation that moves at the speed of sight.
