the other negative, in two opposite
directions through the wire. The presence of these currents evokes a
force of repulsion between the magnet and the wire; and to cause the one
to approach the other, this repulsion must be overcome. The overcoming
of this repulsion is, in fact, the work done in separating and impelling
the two electricities. When the wire is moved away from the magnet, a
Scheidungs-Kraft, or separating force, also comes into play; but now it
is an attraction that has to be surmounted. In surmounting it, currents
are developed in directions opposed to the former; positive takes the
place of negative, and negative the place of positive; the overcoming of
the attraction being the work done in separating and impelling the two
electricities.

The mechanical action occurring here is different from that occurring
where a sphere of soft iron is withdrawn from a magnet, and again
attracted. In this case muscular force is expended during the act of
separation; but the attraction of the magnet effects the reunion. In the
case of the moving wire also we overcome a resistance in separating it
from the magnet, and thus far the action is mechanically the same as the
separation of the sphere of iron. But after the wire has ceased moving,
the attraction ceases; and so far from any action occurring similar to
that which draws the iron sphere back to the magnet, we have to overcome
a repulsion to bring them together.

There is no potential energy conferred either by the removal or by
the approach of the wire, and the only power really transformed or
converted, in the experiment, is muscular power. Nothing that could in
strictness be called a conversion of magnetism into electricity occurs.
The muscular oxidation that moves the wire fails to produce within the
muscle its due amount of heat, a portion of that heat, equivalent to the
resistance overcome, appearing in the moving wire instead.

Is this effect an attraction and a repulsion at a distance? If so, why
should both cease when the wire ceases to move? In fact, the deportment
of the wire resembles far more that of a body moving in a resisting
medium than anything else; the resistance ceasing when the motion is
suspended. Let us imagine the case of a liquid so mobile that the hand
may be passed through it to and fro, without encountering any sensible
resistance. It resembles the motion of a conductor in the unexcited
field of an electro-magnet. Now, let us suppose a