Since that, however, several lines have been built in England that have continued to work successfully; and in Germany successful under-ground cables have been laid down connecting together all of the principal cities of the empire. 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 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. The great trouble with all of these systems, whether in England or on the Continent, was due to water, which found its way to the conductors, and of course destroyed the insulation. If the signals on one wire of such a cable be sharp and quick, they cause fac-simile signals on all of the neighboring wires, and this too, though the insulation may be absolutely perfect; indeed, above a certain point, the more perfect the insulation the greater the induction. 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. The route she was to follow was marked by a line of buoys and flags.

The route was especially selected through a low and marshy section of country, so that the pipes were almost constantly filled with water-this being the best possible condition for the preservation of the gutta-percha. In 1855 the French government, having failed in their attempt to use gutta-percha wires, laid down a large number of bare wires in a trench filled in with bituminous compounds. I currently have a number of examples of these telephones, and as I get the time, I will be posting photos of AE phones in my collection. A brief review of some of the European systems that have been constructed will convince us of this. Systems Safety Technology Division, Sandia National Laboratories. 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. In the cities, pole lines have been considered objectionable, because they disfigure the streets. 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.

Electric-lighting wires, we have seen, are not affected. It consists of seven copper wires, each coated with two layers of gutta-percha and two of Chatterton's compound, and the whole covered with an armor of galvanized-iron wires. The result of this phenomenon is, that messages sent over one wire are liable to be received on all of the other wires, and, in the case of the telephone, this phenomenon is noticeable on cables one thousand feet long, and on a cable one mile long the parties on one wire can easily understand what those on the other wires are saying. 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, what is electric cable besides many other under-ground lines in various parts of Europe. We do not say whether it is twenty million years or more, or less, but me say it is not indefinite.

In 1852 asimilar cable was laid in Russia, between St. Petersburg and Moscow; this worked a few years and then failed. The two firms worked quite independently of one another, and as a result of this the cable could not be tested electrically as a whole length until it was in the cable tanks of the ships employed in laying it ; again, one firm adopted a left-handed lay for the iron wire sheathing, and the other a right-handed. This system, costing from eight to ten times that of a thoroughly built pole line, never worked satisfactorily, and soon had to be abandoned. Some of these lines began to fail almost as soon as completed, while others were, by constant repairing and attention, kept working for nearly ten years, when the whole was finally abandoned and overhead lines put up. The cost of this system was at least ten times that of well-constructed overhead lines. The cost of one wire by itself is vastly larger than where many are run together, the cost of the pipe and for laying being not much greater for fifty wires than for one, and the cost of single wire cables being greater per mile of wire than multiple wire cables, so that the expense of putting such a system as one of our telephone exchanges entirely under-ground would place the cost of the instruments entirely out of reach of the subscribers.