Pop Goes the Cable: More History
     

Over the last few months, most recently in the Oct. 23 issue, we've been looking at the history of wire and cable.

In 1837, Samuel F.B. Morse (1791-1872) demonstrated the first crude "recording telegraph" using his Morse Code. By 1843, he had perfected, patented and sold the idea to the U.S. government, which had requested a telegraph line from Baltimore to Washington, D.C. The secret, as we now know, is that you only need one wire to send the signal because the other wire is the ground itself.

At first Morse considered burying the telegraph wire. Experiments showed that this was more difficult than he had first thought.

For one thing, the wire would need to be insulated so that it does not connect to "ground." The best material around is gutta-percha, uncured rubber. But Morse didn't realize that the dielectric constant of gutta-percha when the wire is suspended is a lot worse than the dielectric constant of air.

A buried wire will have many times the capacitance of a suspended wire. A higher dielectric constant would round off or smear the dots and dashes. Those dots and dashes we might recognize today as a crude square wave, and the capacitance of a suspended wire is much lower than a buried one. So he resigned himself to suspending the wire on poles, and the telegraph pole was born.

On May 24, 1844, Morse tapped out the immortal, and fairly egotistical, words, "What hath God wrought?" Within a very few years, telegraph poles crisscrossed America, and the same was happening all over Europe. Morse eventually bought up a number of telegraph companies in western New York State, and Western Union was born.

These wires were almost all iron, not copper. Copper is a soft metal and cannot support its own weight in long distances from pole to pole. Iron has five times the resistance of copper. That simply means the iron wire must be larger to reduce resistance, or the supply voltage must be a bit higher, more batteries in series.

High-purity copper, and the annealing to give it flexibility, had not been invented. Remember our iceman's ax, with its copper blade 99.7 percent pure? If only we had not lost that technology from 3,000 B.C.

If you're ever in San Francisco, you can visit an excellent display of early telegraph instruments, and even telegraph wire, at the Wells Fargo History Museum at 420 Montgomery Street.

Down the line

While our intrepid heroes were playing with the telegraph wires, many others were studying the effect of electricity traveling down wires.

One was Michael Faraday (1791-1867), who determined that capacitance in wire is related directly to the insulation covering in the wire. In 1837, he proposed that each insulation material has a "dielectric constant" that described how good an insulator it is. By 1854, he also suggested that this constant determined the velocity of a signal traveling down a wire.

Pretty good for a bookbinder's apprentice. He got fired from that job because he kept reading the books he was supposed to be binding, especially the scientific ones. In 1812, he applied for a job as an assistant to one of the foremost scientists in England, Sir Humphrey Davy, based entirely on his reading, and got the job.

In 1857, Gustav Kirchoff (1824-1887) proposed that inductance also was a factor in the speed of signals down wires and that the velocity of a signal on a wire approaches the speed of light when all other factors are minimized.

By the 1850s, there was considerable speculation on running a telegraph wire across the Atlantic Ocean. As early as 1844, Morse had said, "A telegraphic communication line could certainly be established across the Atlantic Ocean." The problem, of course, was the vast distance from Newfoundland to Ireland.

Lieutenant Matthew F. Maury of the Washington National Observatory, perhaps the greatest oceanographer of his time, said, "I do not, however, pretend to consider the question as to the possibility of finding a time calm enough, the sea smooth enough, a wire long enough, or a ship big enough to lay a coil of wire sixteen hundred miles in length."

But he did discover that the ocean floor between Ireland and Newfoundland is mostly one huge plateau. Maury, in a letter to the Secretary of the Navy, said this plateau "seems to have been placed there especially for the purpose of holding the wires of a submarine telegraph and of keeping them out of harm's way."

Pay it out

Between 1856 and 1858, there were four attempts to lay a telegraph cable across the Atlantic Ocean. All failed. There were six cable breaks alone.

Once, in 1857, the brake on a giant reel failed and stalled the reel, which then broke the wire. This incident inspired the following poem:


Pay it out, Oh! Pay it out,

As long as you are able;

For if you put the darned brakes on

Pop goes the cable.


Another time, the brake failed to stop the reel and the end of the cable ran off the end of the ship and into 2,000 feet of water. Still another time the chief engineer, Dr. Wildman Whitehouse, convinced that a huge voltage would be required to communicate over so long a distance, attached his high-voltage dynamos to the cable on the English side, and promptly ruined the first 20 miles of cable.

In 1858, New York businessman Cyrus Field succeeded in laying a cable the entire way, but it only worked for about four weeks.

There is an excellent description of the sordid details of these attempts in the book "How the World Was One" by the noted science-fiction writer Sir Arthur C. Clarke, from which our poem also was taken.

As Maury pointed out, one of the key problems was finding a ship big enough to carry the wire.

And here into our story enters an unforgettable fellow, Isambard Kingdom Brunel (1806-1859).

Brunel was a driven man. Learning mathematics and engineering in his father's firm, he was famous as a bridge designer and builder. He even became famous for his hats, and many in London would sport a Brunel Hat in the 1850s. It inspired the hat worn by the Mad Hatter of "Alice in Wonderland."

Brunel was obsessed. What was the nature of this obsession, and what does it have to do with wire and cable? Tune in next time for a further exciting chapter.

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That previous poster has a good point.
By Anonymous on 10/26/2010

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