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 209
re for each, and therefore to the amount ofelectricity which passes. In comparing the powerof different batteries, — a matter now of some prac-tical importance, — this instrument gives a rapid anduniform result. 308. Instead of using a long coil of wire, sur-rounding the magnet, in estimating… … the magnetometer is represented in Fig. 133. Inthis, the axial attraction of a double helix is made ELECTRO —MAGNETIC TELEGRAPH. 193 use of, as in the Axial Galvanometer invented by Dr.Page, and described in Sillimans Journal, vol. xlix.p, 136. In other respects, the construction is en-tirely…
