LAYING A MILITARY FIELD TELEGRAPH LINE.
The 1st Division of the Royal Engineers, Telegraph Battalion, now encamped at Chevening, close to Lord Stanhope's park, as a summer exercise is engaged in running a military telegraph field line from Aldershot to Chatham. Along the whole of the line the wire is supported on light fir and bamboo poles. The work has been carried out with unusual celerity. From Aldershot to Chevening, a distance of fifty miles, the line was erected in a day and a quarter, or under thirty hours, the detachments employed having worked or marched all night. This is, it is said, the greatest length of telegraph line ever laid within so short a time. The result cannot fail to be useful, for by the new line communication is now established both by telegraph and telephone between Aldershot and Chatham. For laying such telegraph lines to accompany calvary, a light cable is made use of. This is carried on reels on a wheeled cart, and can be laid at the rate of six to seven miles an hour. The Telegraph Battalion of the Royal Engineers comprises two divisions. One is employed in time of peace under the Post Office in the construction and maintenance of postal lines; the other, stationed at Aldershot, is equipped with field telegraph material.—Daily Graphic.
AN ELECTROSTATIC SAFETY DEVICE.
This device, as shown in the accompanying illustration, is a glass cylinder fixed on an ebonite base, and closed at the top by an ebonite cap. A solid brass rod runs from top to bottom, and near the bottom, and at right angles to it, is fixed a smaller adjustable rod, terminating in a flat head. Opposite to this flat disk there is a brass strip secured to the ebonite cap. From the top of this brass strip hangs a gold or aluminum foil. The foil and strip are placed to earth, and the solid brass rod is connected to the circuit to be protected. Should the difference of potential between the foil and the terminal opposite to it attain more than a certain amount, electrostatic attraction will cause the foil to touch the disk and place the circuit to earth. The apparatus, which is a modification of the Cardew earthing device, is constructed by Messrs. Drake & Gorham, of Victoria Street.—The Electrician.
EXPERIMENTS WITH HIGH TENSION ALTERNATING CURRENTS.
Messrs. Siemens and Halske, of Berlin, recently invited the members of the Elektrotechnische Verein of that city to their works to witness the demonstration of a series of experiments on alternating currents under a pressure of 20,000 volts. In order to show that the desired pressure was really en evidence, the high tension was conducted through a pair of wires of only 0.2 mm. diameter to a battery of 200 100-volt incandescent lamps, all connected up in series. An ordinary Siemens electric light cable was inserted, and broke down at a pressure of some 15,000 volts.