ELECTOKS. 746 ELECTRICAL MACHINE. especial legal powers beyond that of election, but lliiough that they exercised a stronj; inlluence on inii)erial affairs. The German i)rinces held that an election as King of the Konians by the German electors was also an election as Holy Roman Emperor: but the pojjcs oon- tendcd that they alone, as vicars of (iod, could bestow the imperial dignity. The Peace of Westphalia (1G4S) created an eighth electorate for the heirs of the Count Palatine, Frederick V., who had been despoiled of his elec- torate in behalf of the Duke of Bavaria in the Thirty Years' War. A ninth, that of IJrunswick- Liineburg, was created in 1()!)2. and fully estab- lished in 1710, as the electorate of Hanover. In 1777 the inheritance of Uavaria by the Elector Palatine restored the number to eight. In 1803, just before the dissolution of the Holy Roman Empire, changes were made, the number being increased. AuKmg the rulers raised at tliis time to the dignity of elector was the Landgrave of Hesse-Cassel, in who.se house the title was re- tained till the extinction of the State in 1806. From the fifteenth century the electors consti- tuted a separate college in the Imperial Diet. Consult: Bryce. The Ilolij Roiiiun Em]nrc (Lon- don, lSfl'2) :'Tunier, The Germanic Constitution (Xew York, 1888). The Golden Bull is trans- lated in Henderson, Select Historical Documents of the Middle Ages (London, 1892). See Holy Roman Ejipire. ELEC'TRA (Lat., from Gk. 'HX^/irpo) . In Greek legend: (1) The daughter of Agamemnon and Clytenuiestra, and the sister of Orestes and Iphigenia. 'hile Agamemlion was absent at the siege of Troy, his cousin .J^gisthus eorrujited Clytemnestra, and, on the great leader's return, shamefully assisted her in - murdering him. Eleetra, alarmed for the safety of Orestes, and desiring to have in him an avenger, contrived to send him to his unele Strophius, King of Phoeis. There lie met Pyladis. and formed with him the friendship so famed in story — an at- tachment further cemented by the marriage of his friend to his sister. There is a tradition that -Egisthus sought to humble her by forcing her to marry a peasant, but the fellow, mind/ul of the gods, duly restored her to Orestes. By Pylades she was mother of Strophius and ilcdon. Her experiences are recounted by .Eschylus in the Choephoi, by Sophocles in Eleetra. by Eurip- ides in the three dramas Eleetra, Orestes, and Iphigenia Among the Tauri. by Racine in Elec- tro, and by Goethe in Iphigenie auf Tauris. (2) Wife of Atlas, by Zeus, mother of Dardanus, and one of the "Oeeanides. (.3) One of the Pleiades, daughter of Atlas and Pleione. See Agamemno.n: Orestes: Iphigenia; and -Egis- TIIUS. ELECTRA, :*i-l.M<'tra. A drama by Galdfis. presented at the Teatro Espafiol in Madrid on January 30. 1(101. This play gave GaUios an opportunity of advancing his lil)eral ideas, and has maile a deep impression in Spain. ELECTRICAL MACHINE (from elretric. from Lat. clrrtrnin. Gk. ^XfKTpof, elektron.amhcT; connected with r/UKTup. r-lektr.r, bright sun. Skt. arha. sm. from arc. to shinel. An instrument which generates electricity by friction or by the inductive action of one set of conductors on another. It is believed that the earliest known form was that of Otto von Guericke. which is described and illu.-.lrated in bis work Expert- menta Sova (Amsterdam. 1G72). a drawing from which is reproduced in Fig. 1. It consisted of a ball of sulphur mounted on an axle which could l)e re- volve(i. The dry hand of the experimenter was placed in contact with the sulphur sphere, which Fig. 1. vox guericke's electric.vl m.vchine. was electrified by the friction thus developed. In Gravesande's Physices Eletncnta (1720) is described an electrical machine where the ball of suljihur is replaced by a hollow glass sphere which is rotated by means of cords or belts con- nected with a wheel and crank. In this ap- paratus threads are provided which are attracted to the charged sphere to show its electrification. In 1744 the electrical machine was improved by Bose of Wittenberg, who introduced a metallic conductor, by means of which the electricity could be conducted from the spliere to the earth and produce a spark on its way. In the same Fig 2. SIMPLE FRICTIONAL MAriUNE. year Winkler of Leipzig devised a machine with a cylinder of glass instead of a sphere, and sub- stituted for the hand two pieces of wool or leather to rub against the glass. Subsequent developments in the eighteenth century included devices to rotate the cylinder, eollccting combs or conductors with points, the use of amalgam on the rubbing surfaces, and, finally, the sub- stitution of a disk of glass for the cylinder and sphere previously employed. In its usual form the frictional machine, as these early pieces of apparatus were termed, is shown in Fig. 2. The glass disk is electrified
