Page:Collier's New Encyclopedia v. 03.djvu/568

LEFT ELECTBIC LAMP 494 ELECTRIC LIGHT method of application is to exercise atrophied muscles and secure their nutrition. In surgery the electrolytic action of the galvanic current destroys tumors and abnormal growths in the nasal cavity. The galvanic current is also used in heating a cautery for sear- ing a surface to secure a cicatrix. The use of faradic electricity is us- ually for its tonic effect. The continued passage of the interrupted currents acts chiefly as a mechanical stimulant, iirst exciting, and after a time depressing the vitality of the parts in the circuit. Vi- brations produced by purely mechanical means, without the use of electricity, may be made to cause very similar effects. Faradization is especially appli- cable to those diseases in which a defi- ciency of functional energy is involved, as in mild cases of spinal and peripheral paralysis. Changes of circulation or of the molecular state may be excited in the central organs by reflex irritation. It has also been used with good eifect in the treatment of gout, rheumatism, widespread ecezma, and constipation, when due to indigestion. Galvanic electricity, however, will also produce all the effects due to the faradic current, but to a very much higher degree. ELECTRIC LAMP. Light. See Electric ELECTRIC LIGHT, a brilliant light emitted by the white-hot points of two pieces of carbon when used as the elec- trodes of a powerful voltaic battery, or other generator of electric currents; also the light emitted by the incandes- cence of a metallic wire, or carbon fila- ment, when subjected to the passage of an electric current. In 1809 Sir Humphry Davy, while experimenting with a powerful battery, discovered the phenomenon of the vol- taic arc. He used as electrodes points of charcoal. Foucault and later experi- menters replaced these by pencils of gas- retort carbon, and this material is yet used in some forms of regulators. A better residt, however, is obtained from manufactured carbon pencils, and this naanufacture already represents a dis- tinct trade both here and in Europe. Coke, lampblack, cane sugar, etc., are the ingredients used for these pencils, which are subsequently placed in molds and submitted to a red heat. The discovery by Faraday (1830) that an electric current could be induced in a coil of wire by the approach to it or recession from it of a magnet may be said to have given electricians the first hope of giving the electric light a com- mercial importance. The magneto-elec- tric machines which followed upon Fara- day's discovery were soon many in num- ber, each one exhibiting some improve- ment upon its predecessor. Of these pioneer machines may be mentioned that of Siemens, who in 1854 introduced a new form of armature or coil, which superseded the bobbins formerly used; Wilde, of Manchester, who produced a powerful machine in which the electro- magnet was first employed in this con- nection, it being excited by a permanent or ordinary horseshoe magnet. In England the Gramme machine was first used in 1874, to provide a light for the summit of the Westminster clock tower. Since that date it has been greatly improved. The Gramme ma- chine gives a continuous current like that afforded by a voltaic battery. An electric current sent through a bridge of vapor or arc between electrode con- ductors produces the arc light. A varia- ELECTRIC LIGHT — TYPES OF ELECTRIC BULBS 1. Carbon Lamp 2. Mazda Lamp 3. New Mazda tion is the incandescent lamp in which a wire of carbon or metal of more or less resistance is mounted in an exhausted glass bulb. The reaction of the filament to the current generates a heat which glows into vivid incandescence. Djmamos moved by water power, gas or steam, generate the electric current at a central station or plant of more or less dimen- sions according to the volume of current in requisition. The organization of high- voltage power has made it possible tc distribute electric current over an ever- widening radius. In cities in the United States the stations of the electric light- ing systems have been shown to be capa- ble of development to the extent of transmitting current over whatever area required, but the clearest demonstration is made by the power stations at Ni- agara, from which center current is transmitted to cities in some cases al- most 200 miles distant. There is per- haps no larger electric-lighting system in any country than that owned in Chi«