Voltaic Induction. : 31 
The deflection may be supposed to be equally good in soft: iron, 
but that the coercive force is feeble, so that the rotation soon ceases ; 
whereas, in unmagnetic: metals, it is probable that there is neither 
deflection nor coercion, and that in consequence of this difference, 
they can receive magnetic induction only by an extraneous motion, 
either of the magnet or the metallic body, so as to imitate the deflec- 
tion. 
Upon this inequality of the inductive process at the opposite sides 
of every particle, rests my hypothesis ; I shall, therefore proceed to 
notice its application to unmagnetic metals, more particularly. 
That motion is necessary for voltaic induction is now demonstrated 
beyond a doubt. Ampere™* has satisfactorily shown that when one he- 
lix, connected with a voltaic battery (and therefore highly charged with 
magnetism in an active state of motion both around and along the circuit 
wire) is introduced within another helix, connected with the galvanom- 
eter, no currents are produced in the latter, while at rest; but, upon 
the slightest movement along the axis either to or from the galvanom- 
eter helix, they become at once apparent and continue during the 
motion. Upon entering the helix and upon leaving it, opposite cur- 
rents are produced ; a fact that cannot well be explained by refer- 
ence to the current of the battery, which never changed. M. Fara- 
day, as far as I understand his views, supposes that during the 
approach, the galvanometer helix gains what he calls electric tension, 
producing a current of one denomination, and that upon reversing 
the motion, this tension is either destroyed by re-action or reversed, 
so as to occasion a current of an opposite character. Observations 
from so sagacious an inquirer are not to be viewed negligently, but 
I hope to make it apparent that such opposite currents admit of expla- 
nation without the necessity of adopting so purely hypothetical a con- 
dition of matter. Considering the magnet and electro-dynamic 
cylinder to effect magnetic induction upon similar principles, [ shall 
confine my illustrations to the former. 
Let N, fig. 4, represent the north pole of a magnet and Nz, Na’, 
Nw” lines of action. Now if we imagine two particles of copper 
aa’ to be placed between them, but at rest, these forces must act 
with equal energy upon all the opposite surfaces, supposing no deflec- 
tion to take place ; and, as all of them operate from the same point 
N, no magnetic induction sufficient to occasion rotation, can ensue. 
* Annales de Chimie, &c. December, 1831. 
