Electro-Magnetic Experiments. 405 
sustain between six hundred and seven hundred pounds. The wire 
was wound upon itself so as to occupy only about one inch of the 
length of the armature which is seven inches in all. The armature, 
thus furnished with the wire, was placed in its proper position across 
the ends of the galvanic magnet, and there fastened so that no motion 
could take place. The two projecting ends of the helix were dip- 
ped into two cups of mercury, and there connected with a distant 
galvanometer by means of two copper wires, each about forty feet 
ong. This arrangement being completed, I stationed myself near 
the galvanometer and directed an assistant at a given word to immerse 
suddenly, in a vessel of dilute acid, the galvanic battery attached to 
the magnet. At the instant of immersion, the north end of the nee- 
dle was deflected 30° to the west, indicating a current of electricity 
from the helix surrounding the armature. e effect, however, ap- 
peared only as a single impulse, for the needle, after a few oscillations, 
resumed its former undisturbed position in the magnetic meridian, 
although the galvanic action of the battery, and consequently the 
magnetic power was still continued. I was, however, much surprised 
to see the needle suddenly deflected from a state of rest to about 
20° to the east, or in a contrary direction when the battery was with- 
drawn from the-acid, and again deflected to the west when it was re- 
immersed. This operation was repeated many times in succession, 
and uniformly with the same result, the armature, the whole time, 
remaining immoveably attached to the poles of the magnet, no motion 
being required to produce the effect, as it appeared to take place only 
in conséquence of the instantaneous development of the magnetic 
action in one, and the sudden cessation of it in the other. 
This experiment illustrates most strikingly the reciprocal action of 
the two principles of electricity and magnetism, if indeed it does not 
establish their absolute identity. In the first place, magnetism is de- 
veloped in the soft iron of the galvanic magnet by the action of the 
currents of electricity from the battery, and secondly the armature, 
rendered magnetic by contact with the poles of the magnet, induces 
in its turn, currents of electricity in the helix which surrounds it; we 
have thus as it were electricity converted into magnetism and this 
magnetism again into electricity. 
Another fact was observed which is somewhat interesting in as much 
as it serves, in some respects, to generalize the phenomena. After the 
battery had been withdrawn from the acid, and the needle of the gal- 
vanometer suffered to come to a state of rest after the resulting de- 
Vox. XXII.—No. 2. 52 
