Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity (1854)
Davis, Daniel · Boston : Palmer and Hall · leaf 187
al open-ing, will sustain a large mass of tacks or brads whilethe current is flowing through it, as shown in Fig.110. 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… … 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.
