Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . ound the wire and on its axis. By cov-ering the rod with sealing-wax, it no longer conveysany part of the current, but is carried round by therotation of the mercury. If the vertical wire is soarranged as to have freedom of motion, it revolvesin the same direction as the iron bar, the two keepingopposite, and moving round a common centre, 287. Axial Revolving Circle. — By employingtwo curved helices, the axial motion of an iron bar Fig. 118. ^^y ^^ co
Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . ound the wire and on its axis. By cov-ering the rod with sealing-wax, it no longer conveysany part of the current, but is carried round by therotation of the mercury. If the vertical wire is soarranged as to have freedom of motion, it revolvesin the same direction as the iron bar, the two keepingopposite, and moving round a common centre, 287. Axial Revolving Circle. — By employingtwo curved helices, the axial motion of an iron bar Fig. 118. ^^y ^^ converted into a direct rota-tion. In Fig. 118is seen a revolv-ing circle, composedof two semicircularbars, the shaded oneof iron, the otherof brass. This cir-cle is supported byfour grooved fric-tion rollers, so as to move freely within the twocoils. Its circumference is cut into teeth, and its mo-tion is communicated to two smaller toothed wheels,on the axis of one of which is the the current passes, one of the helices be-comes charged, and draws the iron bar within soon as its centre reaches that of the coil, the. 180 D AVI S S MANUAL. current is interrupted; and, as it moves on by itsacquired momentum, the action of the break-piececauses the other helix to be charged, and the ironto be drawn into it. 288. Vibrating Helix. —Instead of a oar movingwithin the helix, the latter may be made to move 2? 1X9. ^^^^ ^^^ ^^^- -^^ ^^® instrument representedin Fig. 119, there isa curved bar of ironof the U form, and thehelix is so suspendedas to pass along oneof its poles. Whenthe coil hangs freely,one of its ends dipsinto a mercury cup onC^ the brass pillar. Theaction of the current makes the iron an electro-magnet, and the helix passes along over the motion lifts the wire out of the mercury, whichbreaks the circuit, and the helix falls back. Theinstrument is similar in principle to the one describedin 187, except that an electro-magnet is employ
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Keywords: ., bookcentury1800, bookdecade1850, booksubjectmagnetism, bookyear18
