ELECTRIC FISH. 751 ELECTRICITY. Electric Propcrtiis of the Torpedo (Philadelphia, 1773). From that date the electric orjians of fishes have been made the object of special study by some of the greatest anatomists and physiolo- gists, among them Jobert de Lamballe, who pub- lished a special work entitled Uts tippurcils clec- triijues des poissons clcctri(]Uts (Paris, 1858), accompanied by a magnificent volume of plates. More recent works arc: Boll, L'elKr cUktrischc Fische (Berlin, 1874) ; Sachs, Untersuchungen am Zitteraal (Leipzig, 1881) ; Fritsch, Die elek- trischen Fische (ib., 18S7-90) : Schonlein, Beo- bachtungen tind Untersuchungen iiber den Schlag com Torpedo (Munich, 1894); Gunther, Study of Fishes (London. 1880) ; Wiedersheim. Com- ptirdtivc Amttoinii of Wrtebratcs (London. 1897). ELECTRIC FURNACE. See Electro-Chem- LSTRY, Ixin STKIAL. ELECTRIC FUZR See Fuze. ELECTRIC GENERATOR. See Dtx.mo- ElECTRIC ilACIIINtHY. ELECTRIC HEATER. A device for the conversion of electricity into heat for purposes of artificial heating. Electric heaters consist essen- tiall,v of coils or circuits of some refractory metal through which the current is passed, these coils or circuits being surrotinded by air or some insulating material, and the whole being placed in a metallic box or radiator, which throws off or radiates the heat produced. In the simplest form of electric heater exposed coils of wire or strips of metal are wound around insulating material or left surrounded by air. Another common form consists of wire or strips of metal imbedded in asbestos, cither in the form of coils or in fiat layers. A third class of heater, to which belong the Leonard. Carpenter, Crompton, and other heaters, is made by iiiiliodding the resistance wire in some fireproof insulation, sttch as enamel or glass. The Tommasi heater consists of a coil of wire imbedded in a material having great latent heat of fusion, such as crystallized acetate of sodium and hvposulphite of sodium. In these heaters the current is turned on until the desired temperature has been reached, and. is then turned off and the latent heat allowed to dissi- pate itself, it is claimed that the heater re- mains active .about four hours after the current is shut ofT. The Prometheus system, extensively used in Germany, consists of fusing a broad strip of rare metal on to an enamel which forms the out- side of the vessel, and passing the current through the metal strip or film. Tests have shown the efficiency of this apparatus to he between 84 and 87 per cent. The Le Roy system consists of inclosing sticks of crystallized carbon in glass tubes. In the Parville heater there are rods of metallic powder mixed with fusible clay, com- pressed under a pressure of 2000 kilograms per square centimeter and baked at a temperature of 13.50° C. The above constructions are used in electric cooking and heating apparatus. Elec- tric heaters have their chief field of usefulness in supplying heat for cooking and for laundry irons and for warming electric cars. Unless elec- tricity is produced at a very low cost, it is not commercially practicable for heating residences or large buildings. Nevertheless it is generally considered that the electric heater has a field of application in heating small olficcs. bathrooms, cold corners of rooms, street railway waiting- rooms, the summer villa on cool evenings, etc. It has the peculiar advantage of being instantly available and portable, and it does not vitiate the atmosphere or make dirt. For heating electric cars the electric heater commends itself for rea- sons that are plainl.v obvious to all. For heating laundry irons it is commonly figured that elec- trically heated and gas-heated irons arc irn a i)ar in economy when gas costs $1.25 per 1000 cubic feet and electricity costs 1 cent per horse-power per hour. Numerous tests and estimates of the efficiency of electric heaters for cooking purposes have been made, and the reader interested will find them adequately siunmarizcd in 11. A. Fos- ter's Electrical Engineer's Pucket-liook (New York, 1901). Generally speaking, it may be con- cluded that the efficiency of electric cooking ap- paratus varies from 60 per cent, to 90 per cent, (for ovens) , depending upon a number of variable conditions, such as time, size, quantity to be heated, and temperature rise. The efficiency of an ordinary cooking-stove using solid fuel is only about 2 per cent., 1"2 per cent, being wasted in obtaining a glowing fire. 70 per cent, going in the chimney, and 16 per cent, being radiated into the room. In a gas-stove, considering that the number of heat units obtainable at a certain price is but small compared with solid fuel, the ventilating current required for the operation alone consumes at least 80 per cent, of the heat units obtained by burning the gas. In the ease of an electrical oven more than 90 per cent, of the heat energv' can be utilized; and thus, al- though possibly 5 to 6 per cent, only of the heat energy of the fuel is present in the electrical energy, 90 per cent, of this, or iVi per cent, of the whole energy, actually goes into the food, and thus the electrical oven is practically twice as economical as any other oven, whether heated by solid fuel or by gas. See Welding; Eij:ctbo- ClIEMISTRY, GeXER.L. ELECTRICITY. Few sciences can claim as great an antiquitv as that of electricitv. It is believed that Thales of .Miletus (C.640-.54G u.c.) knew that amber, after being rubbed, acquired the propert.v of attracting light bodies; and Theophrastus (c.372-287 B.C.), in his treatise On Gems, mentions the fact that this power is not peculiar to amber. No definite scientific in- formation was acquired, however, until the close of the sixteenth century. William Gilbert (q.v.) published in 1600 his great work Dr Mtn/iirte. In this book he used for the first time the terms •electric force' and 'electric attraction,' and dis- tinguished between 'electrics' and "noneleetrics' — the former name being given to bodies which act as amber does when rubbed, the latter to bodies. such as metals, which, when held in the hand and rubbed, do not acquire the pov.er of attraction, lie clearly distinguished between magnetic and electric action, as Cardan (1501-70) had also done before, but in an imperfect manner. Robert Boyle, Sir Isaac Newton, and others made many interesting observations on electrical phenontena, the former showing that electric attraction takes place through a vacuum. Otto von Guericke. the inventor of a rude form of electrical machine (q.v.). al.so discovered electric induction, the phenomena of which were studied with special care by Canton nearly a century later. Hawks- bee made several important advances, being the first til show how to electrify metals by rubbing, and also the fir.st to observe that electric charges
