Page:Popular Science Monthly Volume 24.djvu/519

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THE first telegraph line constructed in this country, from Baltimore to Washington, in 1843, was intended to be laid underground, and the first nine miles was so laid. Four copper wires were each wound with cotton, soaked in shellac, and the whole drawn into a lead tube. This tube was laid in a trench by the side of the rail-road. Hardly was the section completed, however, when water found its way into the joints, destroying the insulation, and the conductors failed. They were accordingly replaced by wires strung on poles, and the rest of the line was constructed in this way.

In England a very similar line was built, along the line of the Great Western Railway, for a distance of thirteen miles out from the city of London. This line failed in exactly the same way as the American lines, and the pipes were dug up and placed on short posts six inches above the ground. They were, however, soon replaced by pole lines.

At various places on the Continent similar experiments were tried, and everywhere with the same results. Thus it happened that, though the first idea of telegraph engineers the world over was to run electric wires under-ground, they were everywhere obliged to string the wires on poles. In England and on the Continent there has always been a strong desire to have a part, at least, of the electric wires under-ground. In the cities, pole lines have been considered objectionable, because they disfigure the streets. Between cities, under-ground lines have been desired, because of their great safety in case of invasion, great secrecy, and reliability in case of storms.

The introduction of gutta-percha, in 1846, accordingly gave a new impetus to under-ground construction, and, though it took years of experimenting and millions of dollars, and though system after system failed in England, Germany, and the rest of Europe, there exists to-day a successful and durable system of under-ground telegraph wires connecting together the principal cities of the German Empire, besides many other under-ground lines in various parts of Europe. Many of the European cities have the telegraph lines carried from the center of the city to the outskirts, under-ground; and, in Paris, not only all of the telegraph lines, but those for electric lights, telephones, and the various other private and municipal lines, are carried in the sewers under the streets of the city.

It must be remembered, however, that these various systems have cost from ten to twenty times as much as similar overhead lines; that, for every mile of under-ground wire, there are many miles on poles;