Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . exterior helix is of fine insulated wire, and can belifted oiF from the other, which it surrounds. Itsends are enclosed in two brass caps, to which theextremities of the wire are soldered. To these capsare attached the screw-cups C and D. A bundle ofannealed iron wires, of which the ends are seen inthe cut, can be removed from the inner helix whendesired. 468. In Fig. 180, the different parts of the instru-ment are shown separately. The exterior helix
Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . exterior helix is of fine insulated wire, and can belifted oiF from the other, which it surrounds. Itsends are enclosed in two brass caps, to which theextremities of the wire are soldered. To these capsare attached the screw-cups C and D. A bundle ofannealed iron wires, of which the ends are seen inthe cut, can be removed from the inner helix whendesired. 468. In Fig. 180, the different parts of the instru-ment are shown separately. The exterior helix, a, isremoved from the inner coil, 6, which is fixed to thebase board. At c is seen a brass tube, within which 288 D A VI s S MANUAL. is the bundle of iron wires, cZ, intended to be intro-duced into the interior helix. For giving the strong- Fig. o- o est shocks, the bundle should fill the hollow of thehelix. The other parts are lettered in correspond-ence with the last figure. 469. The bundle of iron wires being withdrawn,let a wire connected with one pole of a galvanicbattery be fixed in the cup A, and the other batterywire be drawn over the steel rasp. Bright sparkswill be seen, and if metallic handles connected withC and D are grasped in the hands, as represented inFig. 179, slight shocks will be felt on completing thecircuit at the rasp, and stronger ones when it isbroken, as with the instrument described in 402,which is on the same principle. 470. If a rod of soft iron is introduced into the SEPARABLE HELICES. 289 helix, the spark is much increased, brilliant scintilla-tions are produced, and the shock, when the circuit isbroken, becomes powerful. The iron acquires andloses magnetism whenever the current begins orceases to flow, and induces secondary currents inboth of the coils which surround it. In the coars
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Keywords: ., bookcentury1800, bookdecade1850, booksubjectmagnetism, bookyear18
