Lamp, incandescent, candle-power of, 150; cord, adjustable, 151; current for, 150; dental, 151; for desks, 151; for throat, 151; guard for, 151; incandescent, 149; socket, 151; with half shade, 151. Lamp, the arc, 153; how light is produced by, Chap. XXII.; double carbon, 153; hand-feed focussing, 153; for search-lights, 153; 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.