Engines of Our Ingenuity

No. 757:
SEMAPHORE TELEGRAPHY

by John H. Lienhard

Click here for audio of Episode 757.

Today, we visit a once vast technology -- now forgotten. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

Let's think about communication over long distances. When I was a child, long-distance calls were rare extravagances. Overseas calls were only for kings and presidents. Western Union was only for emergencies. The mails served everything else. Today, if I have business in Japan, I use e-mail or the telephone, without a thought.

Our pre-electric history is littered with tales of frustrated communications. The Spanish lost their Armada because a message didn't get through. The Light Brigade charged because Raglan didn't have a walkie talkie.

By 1700, that need began driving a wild array of Rube Goldberg communications systems. Of course long-distance signaling was an ancient art -- Indian smoke-signals, ship semaphore flags.

Then 17th-century science offered improvements. In 1684 Robert Hooke, who'd invented the compound microscope, turned his eye outward instead of inward. He wrote a broad analysis of optical telegraphy -- of the possibilities for visual signaling.

A century later, during the Revolution, France finally put in a semaphore telegraph network. It was system of towers with wagging arms. England followed immediately. We joined by 1800.

The name Telegraph Hill in many American cities comes from those towers, read from afar through telescopes. The name is a last vestige of that forgotten technology.

In an English test, operators relayed a message from London to Plymouth and back in three minutes. It'd gone at the astonishing rate of 170 miles a minute. Sound goes only 12 miles a minute.

Electric telegraphy had also gone through a series of experiments. An author, who signed himself (or could it have been herself?) only as C.M., proposed an electric telegraph in the Scot's Magazine in 1753. Europe had tried a great profusion of electric telegraphs by 1832. Then Morse went to work on what would be the first really workable system.

And we, in our vast country, had to wait for Morse. Semaphore telegraphy was impractical outside a few densely populated areas. We used the pony express instead.

Still, those old semaphore relays were once a huge enterprise -- even in parts of America. In 1852, France was still criss-crossed with a 3000-mile network of 556 semaphore stations. By then, electric telegraphs had been around almost two decades.

In a few years the dying dinosaur of semaphore telegraphy would be utterly gone. In a generation it would be forgotten as well. Only its spawn remains. And, I suppose, your grandchildren may one day ask you, "Grandma, what was Western Union?"

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)


Michaelis, A.R., From Semaphore to Satellite. Geneva: International Telecommunication Union, 1965.


The Engines of Our Ingenuity is Copyright © 1988-1997 by John H. Lienhard.

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