Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . ve inopposite directions. 350. Revolving Wheels.—A better form isshown in Fig. 154, in which the wheels move be- Fi^. 154. tween the poles of a steel U-magnet, whoselegs are brought verynear together. In theseinstruments no mer-cury is used. Fig. 154is similar to the Re-volving Disc ( 184),and would have beendescribed in connec-tion with that, had not^ that part of the volumegone to press before this instrument was contrived. 351. Electro-Magnet, revo
Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . ve inopposite directions. 350. Revolving Wheels.—A better form isshown in Fig. 154, in which the wheels move be- Fi^. 154. tween the poles of a steel U-magnet, whoselegs are brought verynear together. In theseinstruments no mer-cury is used. Fig. 154is similar to the Re-volving Disc ( 184),and would have beendescribed in connec-tion with that, had not^ that part of the volumegone to press before this instrument was contrived. 351. Electro-Magnet, revolving on its Axis.— The instrument represented in Fig. 155, is similarto the one described in •§>• 167, except that the re-volving bar is of iron, enclosed in a helix whichrotates with it. The battery current traverses thehelix and one half of the bar. As the bar becomesan electro-magnet, it revolves like the one repre-sented in Fig. 57, except that the direction of therotation is not changed by reversing the current,since the poles are at the same time reversed. Fromthe power of the magnet, the motion is very MECHANICAL POWER. 221 The revolution of either an electro-magnet or a steel magnet on its axis is properly classed with that of a „. ,^^ conductor around a magnet. When theconductor and mag-net are fastened to-gether, the latter iscarried round by themovement of theformer, as stated in<5. 171. Instead offastening a conduct-ing wire to themagnet, the currentmay be transmittedthrough the magnetitself, with the sameresult. 352. Electro-Magnetism as a Motive Power.—-The great velocity of motion, and the strongattractive force exhibited by many of the small elec-tro-magnetic instruments, naturally suggested theapplication of this power to the purposes of the artsas a mechanical agent; and numerous experimentshave been made with this view, but hitherto withoutsuccess. Professor Henry was the contriver of thefirst instrument whose motion depended upon
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Keywords: ., bookcentury1800, bookdecade1850, booksubjectmagnetism, bookyear18
