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 197
hichbreaks the circuit, and the helix falls back. Theinstrument is similar in principle to the one describedin <§> 187, except that an electro-magnet is employedinstead of a steel magnet. 289. In place of a straight iron bar moving with-in a helix, a bar having the form of the letter Umay be… … DOUBLE AXIAL BELL EN K I N E . 181 in the position indicated by the dotted lines in thecut, witii its poles within the double helix, which is Fig. 120.
