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 304
not much superior to the small ones.Ten pairs of Smees battery, connected as one, arebut little better than one pair. 467. Separable Helices.—In this instrument,which is represented in Fig. 179, there are twohelices entirely separate from each other. The innerone, composed of several strands of… … exterior helix is of fine insulated wire, and can belifted oiF from the other, which it surrounds. Itsends are enclosed in two brass caps, to which theextremities of the wire are soldered. To these capsare attached the screw-cups C and D. A bundle ofannealed iron wires, of which the ends are seen…
