EVOLUTION OF ELECTRICITY FROM MAGNETISM. 
137 
copper, was approached to, or placed between the poles (44.), the needle was 
thrown 80°, 90°, or more, from its natural position. The inductive force was of 
course greater, the nearer the helix, either with or without its iron cylinder, was 
brought to the poles ; but otherwise the same effects were produced, whether 
the helix, &c. was or was not brought into contact with the magnet ; i. e. no 
permanent effect on the galvanometer was produced ; and the effects of approxi- 
mation and removal were the reverse of each other (30.). 
5 1 . When a bolt of copper corresponding to the iron cylinder was introduced, 
no greater effect was produced by the helix than without it. But when a thick 
iron wire was substituted, the magneto-electric induction was rendered sensibly 
greater. 
52. The direction of the electric current produced in all these experiments 
with the helix, was the same as that already described (38.) as obtained with 
the weaker bar magnets. 
53. A spiral containing fourteen feet of copper wire, being connected with 
the galvanometer, and approximated directly towards the marked pole in 
the line of its axis, affected the instrument strongly; the current induced in it 
was in the reverse direction to the current theoretically considered by M. Am- 
pere as existing in the magnet (38.), or as the current in an electro-magnet of 
similar polarity. As the spiral was withdrawn, the induced current was 
reversed. 
54. A similar spiral had the current of eighty pairs of 4-inch plates sent 
through it so as to form an electro-magnet, and then the other spiral connected 
with the galvanometer (53.) approximated to it ; the needle vibrated, indicating 
a current in the galvanometer spiral the reverse of that in the battery spiral 
(18. 26.). On withdrawing the latter spiral, the needle passed in the opposite 
direction. 
55. Single wires, approximated in certain directions towards the magnetic 
pole, had currents induced in them. On their removal, the currents were in- 
verted. In such experiments the wires should not be removed in directions 
different to those in which they were approximated ; for then occasionally 
complicated and irregular effects are produced, the causes of which will be 
very evident in the fourth part of this paper. 
56. All attempts to obtain chemical effects by the induced current of elec- 
MDCCCXXXII. 
T 
