Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . rse direction to those of the coil. If its polarity isnot reversed by the power of the current, it will befound to stand erect in th« axis of the helix, beingrepelled equally from every side, instead of beingattracted to every side, as is stated in J 269 to occurwhen its poles correspond in direction with thoseof the coil. 271. Hel5A€al Rin«. —This is a short helix, con-sisting of several layers of wire, and with a large ™, -^ central opening. It is r
Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . rse direction to those of the coil. If its polarity isnot reversed by the power of the current, it will befound to stand erect in th« axis of the helix, beingrepelled equally from every side, instead of beingattracted to every side, as is stated in J 269 to occurwhen its poles correspond in direction with thoseof the coil. 271. Hel5A€al Rin«. —This is a short helix, con-sisting of several layers of wire, and with a large ™, -^ central opening. It is repre- ^ sented at O, in Fig. 108. The ends of the wire are left free,in order to be inserted intothe cups of the battery. AtD are shown two semicircularpieces of soft iron, providedwith handles for pulling. Thehandles are attached to thesemicircles, by ball and socket joints, to preventthem from being twisted or wrenched by irregularpulling. When connection is made with the bat-tery, and the semicircles are passed within the coil,as shown in the cut, they adhere with very consid-erable force* The induction of magnetism ill these15. 170 DAVISS MANUAL. semicircbs, by means of the current from a thermo-electric battery, has been mentioned in ^ 129. 272. With thicker semicircles, such as are repre- jYg. 109. sented in Fig. 109, the induced magnetism issufficient to supporta hundred weight ormore, even with asmall battery. Themutual attraction be-tween the semicircleswhen near each other,but not in actual con-tact, is comparativelyvery feeble. If theflow of the currentin the coil is stoppedwhile they are appliedto each other, they still continue firmly attached; but if once separated, will not adhere again. 273. A heliacal ring, with a smaller central open-ing, will sustain a large mass of tacks or brads whilethe current is flowing through it, as shown in They adhere together in rings, surroundingeach portion of the circumference, as the filingsenclose the single wi
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Keywords: ., bookcentury1800, bookdecade1850, booksubjectmagnetism, bookyear18
