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 208
t brings us at once to a very usefulinstrument, the Magnetometer, represented in Fig.131. Its use is to measure the magnetizing powerof galvanic currents. The form in which it is nowdescribed is new. It consists of a vertical electro-magnet, of the U form, with an armature above it,attached to the… … the electro-magnet when connected with the batterywhose power is to be determined. The lever is sup-ported on an axis with knife-edge bearings. Thearmature may also be suspended on knife edges at-tached to the beam. On the under surface of thearmature is brazed a thin plate of brass, to preventits…
