The Encyclopedia Americana (1920)/Dielectric

DIELECTRIC, a name applied by Faraday to any medium through or across which electrostatic induction can take place. (See Induction, Electrostatic). Solids, liquids and gases possess this property of transmission, though in differing degrees, and their dielectric value, or specific inductive capacity, is measured by the ratio of the capacity of a condenser in which each may form the insulator, to the capacity of the same condenser with a vacuum as insulator.