Electricity, from the Greek elektron (amber), the name applied originally to the unknown cause of the attractions, repulsions, sparklings, etc., which attend the friction of amber and similar substances. The same cause is now recognized as giving rise, under various circumstances, to many phenomena.

Many attempts have been made to ascertain the true nature of electricity, but it cannot be said that we have yet any sure knowledge of what this subtle agent really is. Electricity behaves as if it were an incompressible fluid substance, but it differs from all known fluids in so many particulars that it may be asserted that whatever else it may be, it is not a fluid in the ordinary sense of the word. Neither is it a form of energy, though electrification as distinguished from electricity certainly is such. Many scientific men hold the view that electricity is the ether itself (the elastic, incompressible medium pervading all space and conveying luminous and other vibrations), and that the phenomena of positive and negative electrifications are due to displacement of the ether at the surfaces of bodies. The researches of Hertz, who, by direct experiment, verified James Clark Maxwell's brilliant theory that electrical action is propagated through space by wave motion in the ether, differing only in respect of wave length and period from the vibrations which constitute light, have been of the utmost value in helping to arrive at a solution of this question. Investigations into the phenomena of electric discharges in high vacua, followed by the discovery of Roentgen of the X-rays, have also thrown great light on the subject.

The applications of electricity are extremely varied. Its employment for telegraphy and electro-metallurgy, for chemical and for medical and physiological purposes, for the production of light to illuminate streets and buildings, for driving vehicles and machinery of various kinds, may be mentioned as examples.

Entry from Everybody's Cyclopedia, 1912.