Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . 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.
Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . 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 wire, in Fig. 106. The poles ofa magnetic needle brought near the coil are attractedand repelled as if its axis were a magnet. Aniron bar becomes strongly magnetic when passedhalf way through it. In ^ 185 is described thepolarity exhibited by a coil when it has freedom of. HELIACAL RING. in motion. The polarity of the helix bears so close aresemblance to that of a magnet, that it is usual to Fig. 110.
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Keywords: ., bookcentury1800, bookdecade1850, booksubjectmagnetism, bookyear18
