In recent times considerable attention has been paid to the subject of laying telegraph cables underground, and various methods have been devised. In some cases the cables have been covered with an armor of iron, and in others they have been inclosed in cast-iron pipes. For telephonic service they are generally inclosed in leaden tubes. What this external envelope shall be that is to protect the wires from injury is a question of the highest importance, since not only the subject of protection is concerned, but also that of cost. It is therefore interesting to note the efforts that are being made in this line of electric industry.
[Illustration: FIG. 1. Section of the Pipe Open.]
[Illustration: FIG. 2. Section of the Pipe Closed.]
Messrs. Delune & Co. have recently taken out a patent for an arrangement consisting of pipes made of beton. The annexed cuts, borrowed from L’Electricite, represent this new system. The pipes, which are provided with a longitudinal opening, are placed end to end and coupled with a cement sleeve. The cables are put in place by simply unwinding them as the work proceeds, and thus all that traction is done away with that they are submitted to when cast iron pipes are used. When once the cables are in place the longitudinal opening is stopped up with cement mortar, and in this way a very tight conduit is obtained whose hardness increases with time. The value of the system therefore depends, as in all cement work, on the care with which the manufacturing is done.
Experiments have been made with the system at Toulouse, by the Minister of Post Offices and Telegraphs, and at Lyons, by the General Society of Telephones. Here, as with all similar questions, no opinion can be pronounced until after a prolonged experience. But we cannot help setting forth the advantages that the system offers. These are, in the first place, a saving of about 50 per cent. over iron pipe, and in the second, a better insulation, and consequently a better protection of the currents against all kinds of disturbance, since a non-conducting mass of cement is here substituted for metal.
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“There is nothing new but what has been forgotten,” said Marie Antoinette to her milliner, Mdlle. Bertin, and what is true of fashion is also somewhat so of science. Shoeing restive horses by the aid of electricity is not new, experiments thereon having been performed as long ago as 1879 by Mr. Defoy, who operated with a small magneto machine.
But the two photographs reproduced in Figs. 1 and 2 have appeared to us curious enough to be submitted to our readers, as illustrating Mr. Defoy’s method of operating with an unruly animal.
[Illustration: FIG. 1.—THE HORSE RECEIVING THE CURRENT.]
The battery used was a small Grenet bichromate of potash pile, which was easy to graduate on account of the depth to which the zinc could be immersed. This pile was connected with the inductor of a small Ruhmkorff coil, whose armature was connected with a snaffle-bit placed in the horse’s mouth.