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Updated: May 9, 2025
They crowded close about him at the telegraph-window while he interpreted with unconscious originality the wonders of electricity. Their eyes rose slowly from the window up and out along the ascending wires to where they mounted the poles and eastward and westward leaped away sinking and rising from insulator to insulator.
Lumber is so high that the local or portable sawmill men will buy the timber by the acre. They will cut the trees and haul the logs. If you decide to cut a tree yourself, a little inquiry will show for what purpose it will bring the highest price. Locust sticks, for example, four to six inches thick, will bring in New York ten or fifteen cents a running foot for insulator pinions.
Could it be that the contrivance which worked so promisingly in the Boston rooms would not work under these other conditions? Perhaps an electric current was too delicate a thing to carry sound very far. Or was it that the force of the vibration filtered off at each insulator along the line until it became too feeble to be heard?
Even such apparent exceptions as vulcanite, an excellent insulator, fall into the law, since, as Graham Bell has recently shown, this substance is remarkably transparent to certain kinds of radiant energy. In 1778, Brugmans of Leyden noticed that if a piece of bismuth was held near either pole of a strong magnet, repulsion occurred. Other observers noticed the same effect in the case of antimony.
An insulated sphere in the middle of a room is to his mind such a coating; the walls are the outer coating, while the air between both is the insulator, across which the charge acts by induction. Without this reaction of the walls upon the sphere you could no more, according to Faraday, charge it with electricity than you could charge a Leyden jar, if its outer coating were removed.
What Barrett had done was soon made clear. By wrapping the wire with loose paper, he had in reality cushioned it with AIR, which is the best possible insulator. Not the paper, but the air in the paper, had improved the cable. More air was added by the omission of the oil.
A good insulator to cover the wire and prevent the electricity from leaking into the water was requisite for the success of a long submarine line. India-rubber had been tried by Jacobi, the Russian electrician, as far back as 1811. He laid a wire insulated with rubber across the Neva at St.
This feature may be easily observed with an ordinary induction coil by taking the primary out, plugging up the end of the tube upon which the secondary is wound, and filling it with some fairly transparent insulator, such as paraffine oil. A primary of a diameter something like six millimetres smaller than the inside of the tube may be inserted in the oil.
In 1854 he introduced the pneumatic dispatch into London, and, in 1856, he patented his well-known double-cup insulator. In 1858, he and Mr. Bright produced the material known as 'Clark's Compound, which is so valuable for protecting submarine cables from rusting in the sea-water. In 1859, Mr.
Now if you intend to use the air gap lightning arrester fasten it to the wall of the building outside of your window, and bring the leading-in wire from the aerial to the top binding post of your arrester and keep it clear of everything as shown at B. If your aerial is on the roof and you have to bring the leading-in wire over the cornice or around a corner fix a porcelain knob insulator to the one or the other and fasten the wire to it.
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