Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . tum. The circuit isthen renewed, and the magnets continue to revolvein opposite directions. Since the shaft of the lowermagnet sustains the weight of both, the lower onemoves with less speed than the other, in consequenceof the increased friction. Reversal of the poles bya polcchanger is not resorted to, on account of thefeeble repulsion between electro-magnets. 349. Revolving Wheels, with — In the instrument represented in Fig. 153,
Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . tum. The circuit isthen renewed, and the magnets continue to revolvein opposite directions. Since the shaft of the lowermagnet sustains the weight of both, the lower onemoves with less speed than the other, in consequenceof the increased friction. Reversal of the poles bya polcchanger is not resorted to, on account of thefeeble repulsion between electro-magnets. 349. Revolving Wheels, with — In the instrument represented in Fig. 153, Fig. 153. motion is obtained on thesame principle as in theRevolving Spur-Wheel(§ 180), an electro-magnettaking the place of the steelmagnet. There are twowheels ; of these, the up-per and larger one is partlysupported by springs, itscircumference resting onthat of the smaller current traverses in succession the coil of theelectro-magnet and the wheels. It passes from theaxis of the smaller wheel to that part of its circum-ference which touches the circumference of the other,and thence to the axis of the larger one. The lower. 220 DAVISS MAN UAL . wheel is not merely carried round by the other, butthose parts of both which are conveying the ^Airrenttend to move away from between the poles in thesame direction, causing the two wheels to revolve 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 wh
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Keywords: ., bookcentury1800, bookdecade1850, booksubjectmagnetism, bookyear18
