we pour into it a copper solution, and at the same time place in it a
rod of zinc, so that it rests on the side and bottom, though no coating
will form at all when there is no rod present to excite the electric
current. The same phenomena will appear if we deposit a silver coin in
the solution in question: the coin will come out unaffected, unless we
excite affinity by means of a rod of iron. It is under the action of an
electric current that one metal is coated with another. The metal,
copper say, is steeped in a solution of the coating substance, and
connected by means of wires with a galvanic battery, under the action of
which the metal in solution unites with the surface of the plate
immersed in it. Heat also is developed under magnetic influence, and
that often of great intensity. Thus, if we connect the poles of a
voltaic battery by means of a platinum wire, heat will develop to such a
degree that the platinum will almost instantaneously become red hot and
emit a bright light, and that along a wire of some considerable length.
A similar effect is noticeable when we substitute other metals, such as
silver or iron, for platinum. And the _electric light_, which flashes
out rays of sunlike brilliance, is the result of placing a piece of
compact charcoal between the separated but confronting poles of a
powerful galvanic battery, light, developing more at the one pole and
heat more at the other of the incandescent substance.

Kindred, though much milder, results will show themselves under simpler,
though similar, contrivances. A flounder will jump and jerk about
uneasily if we lay it upon a piece of tinfoil and place over it a thin
plate of zinc, and then connect the two with a bent metal rod; which
will happen to an eel also, if we expose it to a gentle current from a
battery.

By means of electric or magnetic action we can separate bodies