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Resting against each of these cylinders is a palladium-faced spring, and similar springs make contact with the shaft between each cylinder. By connecting all these springs in circuit with a galvanometer and revolving the shaft rapidly, a notable deflection is obtained of the galvanometer needle, indicating the production of electrical energy.
The professor employs a helix connected with a battery, and surrounding a portion of the wire in circuit with the galvanometer. The current in the helix magnetizes the circuit wire inclosed, and the galvanometer exhibits the presence of electricity. The experiment helps to prove that magnetism is connected with some molecular change of the magnetized metal. By Dr. C. WILLIAM SIEMENS, F.R.S, Mem.
He used a galvanometer, a very delicate and accurate scientific instrument, in his experiments. This instrument is so finely adjusted that the faintest current will cause a deflection of the registering needle, which is delicately swung on a tiny pivot. If the galvanometer be attached to a human nerve, and the end of the nerve be irritated, the needle will register. Prof.
The whole is placed upon a stand, and shielded from reflected light, but fully exposed to that which is to be measured for actinic intensity. If now a constant current of electricity is passed through the apparatus, as indicated by a galvanometer, the variations of the latter will show the effect produced upon the selenium.
A scale must be prepared, with the zero point at the greatest possible resistance of the selenium, which corresponds with absolute darkness. The greatest effect of the light would be to annul the resistance of the selenium. Consequently, the cylinder must be withdrawn from the circuit to represent this effect; and the maximum deviation of the galvanometer is then to be observed, and marked 100.
Dolbear observes that if a galvanometer is placed between the terminals of a circuit of homogeneous iron wire and heat is applied, no electric effect will be observed; but if the structure of the wire is altered by alternate bending or twisting into a helix, then the galvanometer will indicate a current.
A suppressed scream escaped Violet Winslow. It was too much like what had happened to Mortimer Warrington for her to repress the shudder that swept over her, and an involuntary movement toward him to make sure that it was not real. Still Garrick did not move from his post at the galvanometer. He was taking no chances.
The magnetic key with which the message was sent Produced by its action an electric current which, after traversing the line, passed through a coil and deflected a suspended magnet to the right or left, according to the direction of the current. A mirror attached to the suspension magnified the movement of the needle, and indicated the signals after the manner of the Thomson mirror galvanometer.
The beam of light focused on the thread in the galvanometer passed to the photographic film, intercepted only by the five spindles of the wheel, which turned once a second, thus marking the picture off into exact fifths of a second. The vibrations of the microscopic quartz thread were enormously magnified on the sensitive film by a lens and resulted in producing a long zig-zag, wavy line.
On a table between the windows were some tea things, with a heap of milliner's materials, and a brass candlestick which had been pushed back to make room for a partially unfolded cloth. There was a second table near the door, crowded with coils, batteries, a galvanometer, and other electrical apparatus.
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