Negative Electricity.—This is the reverse condition to the above and is expressed by the sign or symbol-. These two terms are used in the same sense as hot and cold.
Atmospheric electricity is the free electricity of the air which is almost always present in the atmosphere. Its exact cause is unknown. The phenomena of atmospheric electricity are of two kinds; there are the well-known manifestations of thunderstorms; and there are the phenomena of continual slight electrification in the air, best observed when the weather is fine; the aurora constitutes a third branch of the subject.
Dynamic Electricity.—This term is used to define current electricity to distinguish it from static electricity. This is the electricity produced by the dynamo.
Frictional electricity is that produced by the friction of one substance against another.
Resinous Electricity.—This is a term formerly used, in place of negative electricity. The phrase originated in the well known fact that a certain (negative) kind of electricity was produced by rubbing rosin.
Vitreous electricity is a term, formerly used, to describe that kind of electricity (positive) produced by rubbing glass.
Magneto-electricity is electricity in the form of currents flowing along wires; it is electricity derived from the motion of magnets—hence the name.
Voltaic Electricity.—This is electricity produced by the action of the voltaic cell or battery.
Electricity itself is the same thing, or phase of energy, by whatever source it is produced, and the foregoing definitions are given only as a matter of convenience.