Gravitation, law of, 66
Gravity, variation of, 58, 67; center
of, 68
Guericke, Otto von, 31, 41; portrait
of, 32
Gun, 354-mm., in action, 73
Gyrocompass, 83, 223
Hail, formation of, 174
Hardness, 92
Harmony, 347
Hay scales, 120
Headlight, automobile, 400
Heat, mechanical equivalent of,
151 ff.; unit of, 152; produced by
friction, 153; produced by colli-
sion, 154; produced by compres-
sion, 154; specific, 158; of fusion,
161; of vaporization, 181; trans-
ference of, 203
Heating, by hot air, 211; by hot
water, 212; by steam, 213
Heating effects of electric currents,
284, 289
Helium, 45, 445
Helmholtz, 345
Henry, Joseph, portrait of, 246
Henry's law, 104
Hertz, 422, 436; portrait of, 102
Heusler alloys, 216
Hiero, 21
Hirn, 154
Hooke's law, 91
Horse power, 122
Humidity, 175
Huygens, 364, 372; portrait of, 364
Hydraulic elevator, 18
Hydraulic press, 17
Hydraulic ram, 88, 89
Hydrogen thermometer, 132
Hydrometer, 23
Hydrostatic bellows, 447
Hydrostatic paradox, 14
Hygrometry, 173
Ice, manufactured, 201
Ignition, automobile system of, 198,
199
Images, by convex lenses, 378 ff.;
size of, 381; virtual, 382; by con-
cave lenses, 382; in plane mirrors,
383; in convex mirrors, 384, 386;
in concave mirrors, 384, 387,
Parabolic reflector, 400
Parachute, 44
Parallel connections, 270, 280
Parallelogram law, 61
Pascal, 15, 16, 30
Pendulum, force moving, 64; laws
of, 81; compensated, 141
Periscope, 400
Permeability, 217
Perpetual motion, 156
Perrier, 30
Phonograph, 355
Photometers, 374, 376
Pisa, tower of, 72
Pitch, cause of, 325
Pneumatic inkstand, 33
Points, discharging effect of, 234
Polarization, of galvanic cells, 274;
of light, 374
Potential, defined, 237; measure-
ment of, 239, 265; unit of, 277
Spectra, 411 ff.; continuous, 412;
bright-line, 413; pure, 414; solar,
414; X-ray, 447
Spectrum, 403; invisible portions of,
417
Spectrum analysis, 413
Speed, of sound, 320; of light, 357;
of light in water, 369; of electric
waves, 423 ff.
Spinthariscope, 443
Starting box, 304
Steam engine, 189 ff.
Steam turbine, 199
Steelyards, 115
Stereoscope, 398
Storage cells, 281, 283
Strings, laws of, 339
Sublimation, 168
Submarine, 23, 44
Sun, energy derived from, 157; spec-
trum of, 414
Surface tension, 95
Sympathetic electrical vibrations, 421
Sympathetic vibrations of sound,
346 ff.
Tank, British, 190
Telegraph, 259 ff.; wireless, 423 ff.
Telephone, 316 ff.; wireless, 427 ff.
Telescope, astronomical, 396; Yerkes,
365, 396, 397
Temperature, measurement of, 128;
absolute, 134; low, 134
Tenacity, 90
Thermometer, Galileo's, 128; mer-
cury, 129; Fahrenheit, 131; gas,
132-134; alcohol, 132, 134; the
dial, 143
Thermos bottle, 209
Thermoscope, 418
Thermostat, 142
Thomson, 438; portrait of, 440
Three-color printing, 408
Torricelli, experiment of, 28
Tower, high-tension, 241
Transformer, 312-314
Transmission, of pressure, 15; elec-
trical, 312; of sound, 321
Transmission, automobile, 196
Transmitter, telephone, 316, 317
Trowbridge, 418
Tungar rectifier, 314
Turbine, water, 149; steam, 199
White light, nature of, 403
Wind instruments, 349
Windlass, 120, 453
Winds, 207
Wireless telegraphy, 423 ff.
Wireless telephony, 427 ff.
Work, defined, 105; units of, 106;
principle of, 116, 125, 156
Wright, Orville, 317; portrait of, 316
X-ray picture of human thorax, 359
X-ray spectra, 440, 447
X-rays, 439 ff.
Yale lock, 452
Yard, 2
Yerkes telescope, 365, 396, 397
Zeiss binocular, 399
|