capable of passing, there ensues a current of electricity. Such bodies
are called conductors.


What are the sources of currents?

There are currents produced by chemical action called voltaic
currents; by the action of heat, or thermo-electric currents; by the
motion of magnets, or magneto-electric currents.

[Illustration: REMOVING THE EARTH FROM THE CANAL BY MEANS OF
DROMEDARIES.]

[Illustration: OPENING THE SUEZ CANAL--PROCESSION OF SHIPS.]


What is positive and what negative electricity?

No difference in electricity in itself. When a body has more than its
natural amount of electricity, it is said to be charged positively;
when it has less than its natural amount it is negatively charged.


What is a Cell; what a Battery?

If a piece of zinc and copper joined by a wire be dipped in a
liquid--generally weak sulphuric acid--which will act chemically on
the metals, a current is produced. Such an arrangement is called a
couple, or cell. If many cells are connected, then it is called a
battery.