[Gk.] This name was originally applied to certain attractions and repulsions, but the subject has gradually widened so as to include various chemical heating, luminous, magnetic, and mechanical effects. Electricity is considered under the two heads of (1) Statical or Frictional Electricity; and (2) Current or Voltaic Electricity. Statical Electricity. As early as 600 B.C., Thales and other Greek philosophers discovered that amber (hence the name electricity, from Gk. electron, amber) when rubbed with silk attracted light bodies; and about 1600 a.d., Dr. Gilbert found that glass, sulphur, sealing wax, resin, and many other bodies were possessed of the same property. When glass is rubbed with silk, the glass is said to be electrified positively, and the silk, which has been the rubber, negatively; but wax rubbed with silk or flannel is negatively and the silk positively electrified. The existence of two kinds of electricity is shown as follows : A small pith ball is hung by a silk thread from a glass support, forming an electric pendulum. When a glass rod which has been rubbed with silk is brought near the pith ball, the ball is attracted by the glass ; but as soon as it touches it, repulsion follows, and the two separate. If now a stick of sealing-wax be rubbed with silk, and brought up to the pith ball, the latter will be attracted towards the wax although it has just been repelled by the glass. This shows that a pith ball touched by electrified glass is afterwards repelled by the electrified glass, but attracted by electrified sealing-wax. This experiment shows two things: (1)that there are two kinds of electricity; (2) that two bodies charged with like electricities repel one another, and those charged with unlike electricities attract. The electricities here called positive and negative are also known respectively as vitreous and resinous. The electricity produced by friction has great electro-motive force, and is thus capable of overcoming great resistance, and of producing powerful mechanical effects; but it is deficient in quantity, and therefore does not possess a large amount of energy.

Diagram Showing: A, four cells In series ; B, four cells in parallel; and C, three in series with two in parallel.

Diagram Showing: A, four cells In series ; B, four cells in parallel; and C, three in series with two in parallel.