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The most vitally interesting question which the physics of the future has to face is. Is it possible for man to gain con- trol of this tremendous store of subatomic energy and to use it for his own ends ? Such a result does not now seem likely or even possible ; and yet the transformations which the study of physics has wrought in the world within a hundred years were once just as incredible as this. In view of what physics has done, is doing, and can yet do for the progress of the world, can any one be insensible either to its value or to its fascination ? Joseph John Thomson (1850- ) Most conspicuous figure in the development of the " physics of the electron "; born in Manchester, England; educated at Cambridge University; Cavemllsh professor of experimental physics in Cambridge since 1HH4 ; author of a number of books, the most important of which is the Conduction of Kleclricity thmugh Gases, 1903; author or inspirer of much of the recent work, both ex|ierim«ntjil and theoretical, which has thrown light upon the connection between electricity and matter ; worthy representative of tweatietb-oentury physics. INDEX Aberration, chromatic, 451 Absolute temperature, 135 Absolute units, G Absorption, of gases, 125 ff.; spectra, 456 ; of light waves, 461 ; and radia- tion, 464 Acceleration, defined, 26; of gravity, 29 Activity, 161 Aeronauts, height of ascent of, 68, 70 Air, pressure in, 58; weight of, 58; compressibility of, 65 Air brake, 78 Alternator, 319 Amalgamation of zinc plate, 281 Ammeter, 268 Ampere, 267 Anode, 292 Arc light, :^08 ; automatic feed for, 309 Archimedes, principle of, 51 ; portrait of, 52 Armature, ring type, 318, 321; drum type, 318, 322 Artesian wells, 50 Atmosphere, pressure of, 61; extent and character of, 68; height of homogeneous, 69; humidity of, 100 Atoms, energy in, 482 Back E.M.F. in motors, 328 Balance, 7 Balloon, 76 Barometer, mercury, 62; aneroid, 63; von Guericke's, 63; self-register- ing, 68 Batteries, primary, 280; storage, 290 Beats, 361 Becquerel, 477 Bell, electric, 302 Bellows, 79 Binocular vision, 440 Boiler, steam, 188 Boiling points, definition of, 201; effe<*t of pressure on, 20.'j; table of, 212 Boyle's law, str.ted, 66; explained. 86 Brooklyn Bridge, 145 Bunseu, 394 Buoyancy, of liquids, 62; of gases, 76 Caisson, 78 Calories, 175, 183; developed by electric currents, 306 Camera, pin-hole, 4.'i3; photographic, 433 Candle power, defined, 383; of incan- descent lamps, 307; of arc lamp*, 308 Capacity, electric, 251 Capillarity, 113 ff. Cartesian diver, 75 Cathode, defined, 292 Cathode rays, 470 Cells, galvanic, 262; primary, 280; local action in, 281; theory of, 282; bi- chromate, 285; I>aniell, 285; L»- clanchd, 287; dry, 288; combiuatioiu of, 288; storage, 296 Center of gravity, 22 Centrifugal force, Xi Charles, law of, 134 Chemical effe<'ts of currenU, 292 Coefficient of expansion, of gaaes, I'M, V.fl; of liquids, 1-K); of solids, 142 Coherer, 468 Cohesion, 106; properties depending uo. 112 Coils, magnetic, pro|»ertiesof, 299; cur- rents induced in rotating, 316 Cold storage, 214 Color, and wave length, 443; of bodioa, 445; compound, 447; coropleroeo- tary, 44H; of thin fllnu, 449; of pigments, 449 Commutator, 320 Compass, 235 488 484 A FIKST COURSE IN PHYSICS Component, 17 Condensers, 264 Conduction, of heat, 216 ; electric, 240 Conjugate points, 425, 429 Conservation of energy, 179 Convection, 219 Cooling, and evaporation, 100, 210; of a lake, 141; by expansion, 178; artificial, by solution, 207 Cooper-Hewitt lamp, 310 Crane, 160 Critical angle, 400 Crooks, 479 Crystallization, 124 Curie, 479 Currents, wind and ocean, 220; meas- urementof electric, 261 flf. ; effects of electric, 292 ff. ; induced electric, 312 Curvature, defined, 421 ; of mirror, 426 Daniell cell, 285 Declination, or dip, 235 Density, defined, 9; table of, 9; for- mula for, 10; methods of finding, 64 ff.; of air below sea level, 70; of saturated vapor, 94 ; of electric charge, 247 Dew-point, 99 Diffusion, of gases, 83 and 86 ; of liquids, 89; of solids, 105; of light, 396 Discord, 378 Dispersion, 451 Distillation, 210 Diving bell, 77; suit, 78 Doppler's principle, in sound, 352; in light, 459 Dynamo, principle of, 312; rule, 315; alternating-current, 318, 319 ; four- pole direct-current, 322; series-, shunt-, and compound-wound, 323 Dyne, 35 Eccentric, 188 Echo, 354 Edison, 386 Efficiency, defined, 170; of simple machines, 171; of water motors, 172 ; of steam engines, 191 ; of elec- tric lights, 308 ff. ; of transformers, 336 Eiffel Tower, 7 Elasticity, 108 Electric charge, unit of, 239; distribn- tion of, 247 Electrical machines, 257 Electricity, static, 238 ff.; two-fluid theory of, 242 ; current of, 261 ff. Electrolysis, theory of, 282; of water, 293 Electro-magnet, 301 Electromotive force, defined, 271 ; of induction, 315; back, in motors, 328; in secondary circuit, 331; at make and break, 332 Electron theory, 243, 473, 482 Electrophorus, 256 Electroplating, 294 Electroscope, 240, 245 Electrotyping, 295 Energy, defined, 162; potential and kinetic, 162; transformations of, 163 ; formula for, 165 ; of heat, 167 ; conservation of, 179; of sun, 181; expenditure of electric, 305 ; stored in atoms, 482 Engine, steam, 186 ; compound, 190 ; gas, 192 English equivalents of metric units, 5 Equilibrium, defined, 16; stable, 23; neutral, 24 Erg, 147 Ether, 408 Evaporation, effect of temperature on, 90; effect of air on, 96; cooling effect of, 100; freezing by, 102; effect of surface on, 103 ; of solids, 105 ; and boiling, 206 ; intense cold by, 210 Expansion, of gases, 83; of liquids, 89; unequal, of metals, 144; on solidi- fying, 200 Eye, 435 Falling bodies, 28, 29, 31 Faraday, 296, 312 Fields, magnetic, 231 Fluorescence, 465 Focal length, of convex mirror, 420; of cottcave mirror, 426; of convex lens, 428 Force, definition of, 12; method of measuring, 12; composition of; 14 ; resultant of, 14 ; component of, 17 ; centrifugal, 32 ; beneath liquid, 38; lines of, 230; fields of, 231 INDEX 485 Foucault, 390, 412 Foucault currents, 333 Franklin, 249 Fraunhofer lines, 458 Freezing mixtures, 209 Freezing points, table of, 199; of solu- tions, 208 Friction, 167 If. Fundamentals, defined, 371; in pipes, 380 Cralileo, 26, 29, 59, 388; portrait of, frontispiece Galvanic cell, 262 Galvanometer, 266 Gas engine, 192 Gas meter, 80 Gay-Lussac, law of, 138 Geissler tubes, 470 Gilbert, 235, 238 Gram, of mass, 3; of force, 12 Gravitation, law of, 20 Gravity, variation of, 21 ; center of, 22 Gaericke, Otto von, 63, 64, 73 Hardness, 112 Harmony, 366, 378 Heat, mechanical equivalent of, 174; unit of, 175 ; produced by friction, 176 ; produced by collision, 177 ; pro- duced by compression, 177 ; specific, 182 ; of fusion, 196 ; transference of, 216 Heating, by hot air, 224 ; by hot water, 225 Heating effects of electric currents, 305 Helmholtz, 376 Henry, Joseph, 376 Hertz, 467 Hooke's law, 110 Horse power, 161 Humidity, 100 Huygens, 405 Hydraulic elevator, 48 Hydraulic press, 4G Hydrometer, 54, 55 Hydrostatic paradox, 41 Hygrometry, 97 Ice, manufactured, 213 Images, in plane mirrors, 416 ; multiple. 418; in convex mirrors, 419; size of, 422, 425, 430; in concave mir- rors, 423, 427 ; virtual, 426. 430 ; real. 426 ; by convex lenses, 428 ; by con- cave lenses, 431 Incandescent lighting, 307 Incidence, angle of, 395 Inclined plane, 18, 166 Index of refraction, 412 Induction, magnetic, 229, 236; electro- static, 241 ; charging by, 244 ; cur- rent, 312; coil, 330, 333 Inertia, 32 Intensity, of sound, 347 ; of light, 392 Interference, of sound, 361, 363; of light, 405 Ions, 282, 286, 292 Jackscrew, 157 Joule, 147, 176, 179, 307 Kelvin, 136 Kilogram, the standard, 4 Kinetic energy, 162, 165 KirchofF, 459 Laminated cores, 334 Lamps, incandescent, 307 ; Nemst, 300 Lantern, projecting, 4.'M Leclanchc cell. 287 Lenses, 428 ; formula for, 431 ; magni- fying power of, 437; achtomatic, 452 Lenz's law, 313 Level, of water, 44; carpentar'i, 57 Lever, 151 ff. I>5yden jar, XW Light, speed of, .188; Intensity of. 302; reflection of, .'Wft; rcfnictlon of. 398; nature of, 404; Interference of, 400; dispersion of. 451 ; electro- magnetic theory of, 409 Lightning, 249 Lines, of force. 230; isogonic, 20 Liquid-air machine, 212 Liquids, densities of, 9; pretmire In, 38; transmission of preMore by, 45 ; Incomprcaslbllity of, 65 Local action. 281 Locomotive, 189 Loudness of aoond, 347 486 A FIRST COURSE EST PHYSICS Machine, liquid-air, 212 Machines, general law of, 164 ; efficien- cies of, 171 ; electrical, 257 Magdeburg hemispheres, 64 Magnet, natural, 227; poles of, 228; electro-, 301- Magnetism, 227 ff.; nature of , 232 ; ter- restrial, 234 Magnifying power, of lens, 437 ; of tele- scope, 438 ; of microscope, 439 Manometric flames, 374 Mass, unit of, 3 ; measurement of, 9 Matter, three states of, 105 Maxwell, 86, 470 Mechanical advantage, 150 Mechanical equivalent of heat, 174 Melting points, table of, 199 Meter, standard, 3 Michelson, 389, 390, 412 Microscope, 439 Mirrors, 416; convex, 419; concave, 423; formula for, 431 Mixtures, method of, 184 Molecular forces, in solids, 107; in liquids, 113 Molecular motions, in gases, 82; in liquids, 88; in solids, 104 Molecular nature of magnetism, 232 Molecular velocities, 85, 87 Moments of force, 152 Momentum defined, 33 Mont Blanc, 68, 70 Morse, 303 Motion, uniformly accelerated, 25; laws of, 32; perpetual, 180 Motor, electric, principle of, 326 ; street- car, 327 Musical instruments, 384 ff. Newton, law of gravitation, 20; por- trait of, 20; laws of motion of, 32; and corpuscular theory, 405 Niagara, 166 Nodes, in pipes, 364 ; in strings, 370 Noise and music, 351 Nonconductors, of heat, 218; of elec- tricity, 240 Oersted, 263 Ohm, 275, 276 Opera glass, 440 Optical instruments, 433 Organ pipes, 380, 384 Oscillatory discharge, 466 Overtones, 371, 381 Parachute, 77 Parallel connections, 289 Parallelogram law, 16 Pascal, 45, 61 Pendulum, force-moving 19; compen- sated, 143 Permeability, 230 Perrier, 62 Perrotin, 389 Phonograph, 386 Photometers, 393, 394 Pisa, tower of, 29 Pitch, cause of, 352; and wave length, 349 Polarization, of galvanic cells, 284; of light, 415 Potential, defined, 251; unit of, 25;3; measurement of, 254, 269, 272 Power, 161 Pressure, in liquids, 38; defined, 43; in air, 58 ; amount of atmospheric, 61 ; of saturated vapor, 95 ; effect of, on freezing, 202 ; in primary and secondary, 336 Prism, refraction through, 402 Pulley, 48, 148 ff. Pump, air, 73; water, 74; force, 75 Quality of musical notes, 373 Radiation, thermal, 221 ; invisible, 461 ; and temperature, 463; and absorp- tion, 464 ; electrical, 466 Radio-activity, 476 Radiometer, 461 Radium, discovery of, 476; birth of, 481 Rainbow, 452 Ramsey, 480 Rays, infra-red, 461; ultra-violet, 462; cathode, 471 Reflection, of sound, 354 ; of light, 395 ; total, 399, 401 Refraction, of light, 398; by atmos- phere, 404 ; index of, 412 ; explana- tion of, 412 Regelation, 201 Belay, 303 INDEX 487 Resistance, electric, defined, 273; spe- cific, 273 ; unit of, 274 ; laws of, 274 ; internal, 276 ; measurement of, 277 Resonance, acoustical, 357: electrical, 466 Resultant, 14 Retinal fatigue, 449 Right-hand rule, 265, 300 Roemer, 388 Rijutgen, 470, 474 Rowland, 179 Rumford, 393 Rutherford, 478 Saturation, of vapors, 90; of solutions, 122; magnetic, 234 Scales, musical, 366 ; diatonic, 367 Screw, 157 Series connections, 288 Shadows, 391 Shunts, 279 Singing Hame, 378 Siphon, explanation of, 71 ; aspirating, 72 Soap films, 115, 443 Solar spectrum, 457, 463 Solution, of solids, 121 ; effect of evap- orating, 12.3 Sonometers, 369 Sound, sources of, 343; speed of, ^$44; nature of, 346; musical, .'<51 ; re- flection of, 354; foci, 350; interfer- ence of, 361 Sounder, 303 Sounding-boards, 360 Sources of light, 409 Spark, length and potential, 254 Spark, oscillatory nature of, 467; in vacuum, 470 Speaking tubes, 348 Specific gravity, 10 Specific heat, defined, 183; table of, isn Spectra, continuous, 454; bright-lino. 455 Spectrum analysis, 456 Speed, of sound, 343; of light, 388; of light in water, 410; of electric waves, 467 Spinthariscope, 479 Spring, intermittent, 72 Steam, engine, 187 £f. ; turbine, 194 Stereoscope, 440 Strings, laws of, 369 Sun, energy derive<l from, 181 Sympathetic vibrations, of sound, 377; electrical, 466 Telegraph, 302, 304; wireleas, 468 Telephone, 3:» ff. Telcscopc,astronomical,4C8; terrestrial, 439 Temperature, measurement of, 129; absolute, 135; low, 136; critical, 211 Tenacity, 108 Thermometer, Galileo's, 129; mercury, l.'K); Fahrenheit, 131; gas, Vfl; maximum and minimum, 136; tli« dial, 144 Thomson, 243, 472, 482 Toepler-Holtz, 257 Torricelli, experiment of, 60 Transformer, Xi5, 337 Transmission, electrical, 337; of sound, 343 ff. ; of light, 388 Transmitter, telephone, 340 Turbine, water, 173; steam, 194 Units, of length, 1, 2; of area. 2; of volume, 2 ; of mass, 2, 4 ; of time. 6; three fundamental, 5; C.(i.8.. 6; of force, 12, M; of work. 147; of power, 101 ; of heat, 175 ; uf magnetism, 229 ; of electricity, 2X9; of potential, 25:1; of rurrent, 'XI, 296; of resisUuce, 274; of light, 393 Vacuum, sound in, 444 ; spark in, 470 Vaporization, heat of, 203 Velocity, defined, 25; of falling body, 27. :»; of sound, 343; of light, aM Ventilation. 223 Vibration, numbers. 36H; of •trlofi, 369; forced. 300; sympatlietio, 377 Visual angle, 436 Volt. 253 Volla, 263. 250 Voltmeter, 2B9 Water, density of. 3; city supply of, «•; maximum dcnuity of. 140; whwla, 172; expaaakin of, oo tnting, 900 488 A FIRST COURSE IN PHYSICS Watt, 162, 189 Waves, condensational, 349 ; water, 350 ; longitudinal and transverse, 351 ; light, transverse, 413; electric, 467 Wave length, defined, 348 ; formula for, 349; of yellow light, 408; of other lights, 444 Wave theory of light, 404 Weigliing, method of substitution, 8 Weights, 7 Wheel, and axle, 156 ; gear, 158 ; worm, 158; water, 172 White light, nature of, 446 Windlass, 160 Winshurst electrical machine, 259 Wireless telegraphy, 468 Work, defined, 146; units of, 147; principle of, 155 X rays, 474 Yard, 1 Yerkes telescope, 439 Zeiss binocular, 441 Onivenify of Toronto Library Acme Librao' Card Pocket LOWE-MARTIN CO. 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