The wire is now the channel of
what, for want of a better name, we call an 6 electric current.' What
the inner change of the wire is we do not know, but we do know that a
change has occurred, by the external effects produced by the wire. Let
me show you one or two of these effects. Before you is a series of
ten vessels, each with its pair of metals, and I wish to get the added
force of all ten. The arrangement is called a voltaic battery. I
plunge a piece of copper wire among these iron filings; they refuse to
cling to it. I employ the selfsame wire to connect the two ends of
the battery, and subject it to the same test. The iron filings now
crowd round the wire and cling to it. I interrupt the current, and
the filings immediately fall; the power of attraction continues only
so long as the wire connects the two ends of the battery.

Here is a piece of similar wire, overspun with cotton, to prevent the
contact of its various parts, and formed into a coil. I make the coil
part of the wire which connects the two ends of the voltaic battery.
By the attractive force with which it has become suddenly endowed, it
now empties this tool-box of its iron nails. I twist a covered copper
wire round this common poker; connecting the wire with the two ends of
the voltaic battery, the poker is instantly transformed into a strong
magnet. Two flat spirals are here suspended facing each other, about
six inches apart. Sending a current through both spirals, they clash
suddenly together; reversing what is called the direction of the
current in one of the spirals, they fly asunder. All these effects
are due to the power which we name an electric current, and which we
figure as flowing through the wire when the voltaic circuit is
complete.

By the same agent we tear asunder the locked atoms of a chemical
compound. Into this small cell, containing water, dip two thin wires.
A magnified image of the cell is thrown upon the screen before you,
and you see plainly the images of the wires. From a small battery I
send an electric current from wire to wire. Bubbles of gas rise
immediately from each of them, and these are the two gases of which
the water is composed. The oxygen is always liberated on the one
wire, the hydrogen on the other. The gases may be collected either
separately or mixed. I place upon my hand a soap bubble filled with
the mixture of both gases. Applying a taper to the bubble, a loud
explosion is heard. The ato