single carbon,153;short, for basements,153;for theater use,153.Lamp circuits, alternating system,144.Lamps, in parallel,144;lamps in series,144;three-wire system,144;two-wire system,144.Laws, of electrification,7;of magnetic attraction,32;of resistance,70.Leaf electroscopes,5.Leclanché cell,57.Leyden, battery,16;jar,15.Light, how produced by arc lamp,Chap. XXII.;how produced by incandescent lamp,Chap. XXI.Lightning,19;rods,21.Line, telegraph,Chap. XIV.;connections for,111;operation of,112.Line suspension, for trolley-wires,167.Line wire,111.Lines of force, conductors of,39,96;about the earth,40,42;and induced currents,101;about a magnet,38;about a wire,92.Local currents,47.Magnetic, bodies,29;declination,41;effects of electric current,Chap. XI.;field,37;figure of one bar magnet,38;figure of two bar magnets,38;figure of horseshoe magnet,38;needle, dip of,42;needles and compasses,31.Magnetism, and heat,35;induced,36;laws of,32;residual,34;retentivity,34;temporary,36;terrestrial,40;theory of,33.Magneto, signal bells,117;testing bells,117;transmitter,120.Magnets, action upon each other,32;artificial,25;bar,27;compound,28;effects of jarring,33;electro,96;electro, forms of,97;horseshoe,26;and magnetism, about,Chap. II.;making of,30;natural,24.Mains, electric,139.Man-holes, in conduits,140.Measurements, electric,Chap. VI.;of current strength,73;of E.M.F.,67.Meters, chemical,78;permanent record,77.Microphone, the,122.Motion and currents,160.Motor, acting like dynamo,163;armature of,161;controlling speed of,165;electric,161;electric, and how it does work,Chap. XXIV.;fans,162;for automobiles,169;for boats,168;for pumping bellows,162;for running drill press,162;parts of,162;starting boxes for,163;uses of,162.Motor-dynamos,136.Mouldings, for wires,141.Name, electricity, origin of,2.Natural magnets,24.Needles, astatic,94;dipping,42;magnetic,31.Negative electrification,5.Non-conductors,4.North pole, magnetic of earth,40;of magnets,26.Northern lights,23.Ohm, the,69.Open circuit cells,50.Openers, for doors,175.Outfits, dental,175.Overhead trolley system,166.Oxygen, attraction for hydrogen,85.Parallel arrangement of lamps,144.Peltier effect,89.Pendant, electric,151.Pith-ball electroscope,5.Plate electrical machine,10.Plates of cells,45a.Plunge batteries,53;large,54.Polarity of coils,95.Polarization,84;electromotive force of,85;of cells,48.Pole-changing switch,62.Poles, of cells,45a;of horseshoe magnet,26.Positive electrification,6.Potential, defined,65.Push-buttons,Chap. V.;indicating,61;modifications of,61;table clamp,61.Quantity of electricity,76;unit of,76.Rays, cathode,157;x-rays,158.Receiver, telephone,121.Reflectors, for lamps,151.Registers, ink writing,114.Relay, the,113.Residual magnetism,34.Resistance, coils and boxes,69;electrical,68;external,68;and heat,145;internal,68;laws of,70;unit of,69.Retentivity,34.Risers, in buildings,139.Rods, lightning,21.Roentgen, Prof.,158.Rosette, fusible,142.Running-gear, of automobiles,169.Safety, devices,142;fuse,142;fuse link,142;fuse plug,142;fuse ribbon,142;fuse wire,142.Search-lights,153;signals sent by,153.Secondary batteries,86;uses of,87.Series arrangement of lamps,144.Series wound dynamo,131.Service wires,139.Shunt-wound dynamo,131.Signal bells, magneto,117.Simple cell, the,45,49.Single-fluid cells,49.Single-point switch,62.Single-stroke bell,116.Socket, for incandescent lamps,151.Soldering irons, electric,147.Sounders, telegraph,110;home-made,110.Spark, effect of air pressure on,155.Sparks, from cells,17;from frictional electricity,4.St. Elmo's fire,22.Starting boxes, for motors,163.Static electric machines,8.Static electricity, condensation of,15;electromotive force of,17;to test presence of,5;uses of,14.Steam engines, in central stations,170.Steel, inductive influence of earth upon,43;retentivity of,26.Storage batteries, the, and how they work,Chap. IX.;for automobiles,169;for boats,168;for natural sources of power,87.Stoves, electric,147.Strength of current,71;measurement of,73;unit of,72.Switchboards,62.Switches,Chap. V.;knife,62;pole-changing,62;single point,62;for trolley lines,167.Table clamp-push,61.Tangent galvanometer,73.Teakettles, electric,147.Telegraph, electric, and how it sends messages,Chap. XIV.;ink writing registers,114;keys,109;relay,113;sounders,110.Telegraph line,107,108;operation of,112;simple connections of,111.Telephone, the, and how it transmits speech,Chap. XVI.;receiver,121;transmitter,120;use of induction coil with,124;various forms of,125.Temporary magnetism,36.Terrestrial magnetism,40.Theory of magnetism,33.Thermoelectricity,88.Thermopiles,90.Three-wire system,144.Throat, lamp for,151.Thunder,20.Toepler-Holtz machines,11.Transformers,135.Transforming electric current,Chap. XVIII.;for electric welding,146.Transmission of currents,134.Transmitter, Bell,120;carbon,123.Trembling bell,116.Trolley-wires,164;-poles,164;-wheels,164.Tubes, Crookes,156,158;Geissler,156;vacuum,156.Two-fluid cells,49.Two-wire system,144.Underground trolley system 166;conduits for,166.Unit, of current strength,72;of electromotive force,66;of quantity,76;of resistance,69.Units, electrical,Chap. VI.Uses, of armatures,39;of electricity, miscellaneous,Chap. XXVII.;of induction coils,106;of motors,162;of storage batteries,87.Vacuum-tubes,156.Variation, angle of,41.Volt, the,66.Volta,66;early experiments of,44.Voltaic cell, electricity generated by,Chap. III.Voltaic pile,44.Voltameters,75;copper,75;water,75.Voltmeters,67,77.Water, decomposition of,79;power, source of energy,170;voltameters,73.Watt, the,77.Wattmeters,77.Welding, electric,146.Wimshurst electric machine,12.Wires and cables,143.Wiring, for alternating system,144;three-wire system,144;two-wire system,144.Work, and electric current,133.X-ray photographs,159.X-rays,156;and how the bones of the human body are photographed,Chap. XXIII.Yokes,97,98.Zincs, amalgamation of,47.