ELMSLEY, PETER ENFIDAVILLE ELNE ENFIELD (Connecticut, U.S.A.) EL OBEID ENFIELD (England) ELOI, SAINT ENFILADE ELONGATION ENGADINE EL PASO ENGAGED COLUMN ELPHINSTONE, MOUNTSTUART ENGEL, ERNST ELPHINSTONE, WILLIAM ENGEL, JOHANN JAKOB EL RENO ENGELBERG ELSFLETH ENGELBRECHTSDATTER, DORTHE ELSINORE ENGELHARDT, JOHANN GEORG VEIT ELSSLER, FANNY ENGHIEN, LOUIS ANTOINE HENRI ELSTER (rivers of Germany) ENGHIEN ELSTER (spa of Germany) ENGINE ELSWICK ENGINEERING EL TEB ENGINEERS, MILITARY ELTON, CHARLES ISAAC ENGIS ELECTROSTATICS, the name given to that department of electrical science in which the phenomena of electricity at rest are considered. Besides their ordinary condition all bodies are capable of being thrown into a physical state in which they are said to be electrified or charged with electricity. When in this condition they become sources of electric force, and the space round them in which this force is manifested is called an "electric field" (see ELECTRICITY). Electrified bodies exert mechanical forces on each other, creating or tending to create motion, and also induce electric charges on neighbouring surfaces. The reader possessed of no previous knowledge of electrical phenomena will best appreciate the meaning of the terms employed by the aid of a few simple experiments. For this purpose the following apparatus should be provided:--(1) two small metal tea-trays and some clean dry tumblers, the latter preferably varnished with shellac varnish made with alcohol free from water; (2) two sheets of ebonite rather larger than the tea-trays; (3) a rod of sealing-wax or ebonite and a glass tube, also some pieces of silk and flannel; (4) a few small gilt pith balls suspended by dry silk threads; (5) a gold-leaf electroscope, and, if possible, a simple form of quadrant electrometer (see ELECTROSCOPE and ELECTROMETER); (6) some brass balls mounted on the ends of ebonite penholders, and a few tin canisters. With the aid of this apparatus, the principal facts of electrostatics can be experimentally verified, as follows:--