None
Mean value of X '091. Observations for T : 20 double vibrations take 64-5 seconds (same value for each of three observations). T« 3-225 seconds; R = 5000 ohms » 5 X 10" C.G.S units ; G = 5600 „ = 5-6 X io'« C.G.S. units ; Battery i Daniell cell of negligible resistance «= 100. Whence C» ro 12 microfarad. ; ^ t( »l,W>^*-=» ^lA^w*>^ ^Iv^- e^^'^^^ r INDEX. ABS ABSORPTION, electric, 475 — of light, measurement o^ 342 Acceleration due to gravity, method of measuring, 128, 136 Accumulator, 4;jo Acoustics, definitions, &c., 164 Air lines, si>ectrum of, 30a — - thermometer, 20b Alluard, modification of Regnault's hy- grometer, 2^2 Amp&re, definition of, 391 Angle of a wedge of gkiss, measurement of, 292 — of incidence of light on a reflecting surface, 314 — of prism, method of measuring, 308 Angles, measurement of, 80 Approximation, 41 Aqueous vapour, chemical determmation of density of, 233 — — , tension of, 231 Areas, measurement of, 73 Arithmetical manipulation, 36 Arms of a balance, 100 Aspirator, 234 Astatic magnets, 402 Atwood's machine, 133 B .A. wire bridge, 451 — , Fleming's I J ^ , r icuuiiK s fonn of, 459 Balance, adjustment of, 87 — , hydrostatic, 107 — , Jolly's, 120 ^ , ^ — , sensitiveness of the, 84, 97 — , testing adjustments of a, 98 — , theory of the, 83 Ballistic galvanometer, 469, 472 Barometer, aneroid, i57 . , — , comparison of aneroid and mercurj-, — , correction of readings, 155 ^, measurement of height by the, 159 — , mercury, i53 - , Base line, measurement of, 6^ Battery resistance. Mances method, 447 COR Beam-compass, 54 Beats, 165 Binomial theorem, 42 Bi-prism, 319 Bi-quartz, 327 — , method of determining plane of po- I larisation by aid of, 328 , Bird-call, 181 Boiling point, determination of, 193 • , of a liquid, 196 ^ j Borda's method of weighing, loi I Boyle's law, 160 , Bndgc-wire, calibration of a, 460 ! Bunsen's photometer, 244 Buoyancy of air, correction of weighings I for, 103 , Burette, 79 CALIBRATION of a tube, 75 Calipers, 50 Calorimeter, description of, 214 Calorimetry, 211 Capacities, comparison of electrical 471 — , Null method of comparing, 476 * Capacit>', absolute measurement of, 470 — , definition of electrical, 471 ^ — , unit of electrical, ^71 Carey Foster's method of comparine re. sistances, 455 * Clifford, 4 Colour box, 345 — top.* 337 — vision, 337 - -, I^rd Rayleigh's observations on, Commutator, 408 Comparison of^ spectra, 301 Compressibility, 139 Concave mirror, focal length of r,tk. Condenser, definition of ^Sa^ll^lV Condensers, 470 »^Pacity of, 471 Conductivity, 421 Cooline, method of, 225 Comu s prism, 3^ Collections, anihmetical calculation of 484 Index, Current, absolute measure of a, 391 — of electricity, 386 D ALTON'S experiment, 228 — law, 231 Damping, correction for, 469 Density, definition of, 105 — , determination of, by the volumeno- meter, 163 Deviation, position of minimum, 311 Dew point, 253 — _ — , determmation of, 239, 241 Diffraction experiments, 324 — grating, «5 Dimensional equations, 24, 97 Dines's hydrometer, 238 Division, abbreviated form of, 38 Double weighing, too Drying, method of, 1x2 — tubes, 234 EARTH'S magnetic force, measure* mem of, 373, 375 EuLsticity, theory of, 139 Electric battery, 385 — current, 385 — field, 381 Electrical decomposition of water, 411 — force, definition of, 382 — phenomena, 381 — potential, definition of, 383 — qtiantity, 381 — resistance, absolute unit of, 425 , definition of, 421 — • measured by Wheatstonc's bridge, 443 Electricity, conductors of, 382 ^, definitions and explanation of terms, 381 Electrochemical equivalents, 406 , comparison of, 411 Electrodes^ 406 Electrolysis, 406 Electro-magnetic unit current, definition of, 388 Electromotive force, definition of, 383 — — measurement of, 416 ^- forces, methods of comparing, 435 ^ compared by equal deflexion method, 436 compared by equal resistance method, 436 — — , PoggendorflTs method of com- paring, 4J5i Equipotential surfaces, 351 Error, Mean, j4 Error, Probable, 34 Errors, 31 — - calculation of effect of hypothetical — , special sources of, 48 HYG Ether vapour, pressure of, 230 Expansion, 103 — , coefficient of, 198 — ^ measurement of, 109 by a weight tnermometer, 202 — of water, measurement of, 192 Extrapolation, 189 FARADAY'S law of electrolyas, 406 Fluid pressure, measurerocot of, 152 Focal lengths of lenses, 067 Focal lines, 276, 291 Focussing for parallel rays, 281 Forcc^ gravitation measure of, 12 Freezing point, determination of, 193 Frequency of a note, 165 Fresnel's mirrors, 323 Fusing point of a solid, 197 GALVANOMETER, 389. Horizon, artificisU, 258 Humidity, relative, 232 Hydrometer, common, 123 — , Nicholson's, 117 Hygrometer, Dines's, 238 — , Regnault's, 241 Index. 485 IIYG Hygrometry, 231 Hypsometer, 193, 195 IMPULSE due to passage of a quan- tity of electricity, 467 Index of refraction, definition of, 302 , measurement of, with a micro- scope, 303 with a spectrometer, 309 Induction coil, spectrum of spark of an, Inertia, moment of, 144 Interpolation, 41 Ions, 406 T ELLETTS prism, 334 J Jolly's air thermometer, ao8 Jolly's IJalance, xao Joale's law, 416 KATHETOMETER. 66. 125 Kilogramme standard, zi LATENT heat of steam, 221 of water, 2it> Latimer>CIark's potentiometer, 463 Laurent's methoa of measuring position of plane of polarisation, 335 Legaj ohm, 426 Length, apparatus for measuring, 50, 54. 57. 59. 64 Lens, focal length of a long focussed, 293 .^. ^, magnifying power of, 283 Lenses, measurement of focal lengths of, 267, &C. Leyden jar, used with spectroscope and coil, 209 Lippich s method of measuring position of plane of polarisation, ^34 Liquid, measurement of refractive index of, 304, 312 Logarithmic decrement, 469, 479 Lupton, 30 MAGNET and mirror, 391 Ma^etic axis, 348 — declination, measurement of, 375 — fieldL 350 — — cue to a current, 387 , exploration of a, 379 measurement of strength of, 373 — force, laws of, 349 , line of, 350 (measurement of, 364,373 — due to a current, verification of law of, 394 — forces on a magnet, 35s, 359 — induction, 366 369 PAR Magnetic meridian, 348 — moment. 356 , measurement of, 366, 370, 373, — poles, ju8 -■ potential^ 351, 353,358 Magnetisation by divided touch, — of a steel bar, ^67 Magnvdsm, definitions and explanations concerning, 3^8, &c. Magnets, experiments with, 367 — , properties of, 347 MagniKring power of a telescope, 279 of a microscope, 2S3 of a lens, 283 — powers of optical instruments, 278 Mapping a spectrum, 207 MaxwelTs theory of colour, 338 — vibration needle, 146 Mean of observations, 32, 34, 35 ' Measurement, methods of, 2, 5 — , units of, 9 Measurements, approximate, 30 — , possible accuracy of, 35 Mercury, filling a biarometer tube with, 228 Method of mixture, 212 Metre, standard, 1 1 Microscope, magnifying i>ower of, 283 — used to measure refractive indices, 303 Microscopes, travelling, 6^ — used to measure expansion, 200 Mirror telescope and scale, method of adjusting, 147 Moment of inertia, 144 , determination of, 145, 150 Monochord, 275 Morse key, 473, ^81 Multiplication, aobreviated form of, 38 39 Musical note, 164 N ICOL'S prism, 325 , adjustments of, 326 OHM, legal, 426 — practical unit of renstance, 425 Ohm's law, 420 Optical bench, 318 — measurements, general method for some, 259 Oscillation, method of observing time of, 128 Oscillations, method of comparing times of, 132 — , — of weighing by, 91, 97 PARALLAX, method of avoiding error due to, 194 Parallax, optical adjustment by means of, 251, 262, 271 486 Index. PAR Parallel rays, focussing for, 381 Partial tones, 165 Pendulum, 128 Photometer, Bunsen's, 244 — , Rumford's, 248 Photometry, theory of, 243 Physical constants, tables of, 30 — laws, quantitative, 13 — quantities, a , Pitch, absolute, 175 — of tuning forks, comparison of, J65 Plane surface to set a in a given position, 307 ^ — surfaces, optical tests for, 287 Planimeter, 74 Polarimeters, shadow, 332 Polarisation, determination of plane of, 325 — , measurement of position of plane of, 334 — , rotation of plane of, 325 Polarised light, 325 Polarising apparatus, 325 Potential, electrical, 383 — , zero of, 385 — due to a magnet, 358 — of the earth, 384 Potentiometer, 461 Pound standard. 1 1 Poynting's method of measuring the position of the plane of polarisation, 336 Pressure, measurement of fluid, 152 Principal points of a lens, 270, 273 Prism, adjusting a, 297 — , adjustment of, on a spectrometer, 307 — , measurement of angle of, 30* — , measurement of refractive index of, ^309 Pumice stone, 234 /^UANTITV', numerical measure of, — of electricity, galvanometric measure- ment of, 466 RADIUS of cur\-ature, optical mea- surement ot, 261, 263, 290 Reflexion, radius of curvature measured by, 390 — of light, verification of law of, 250, 308 Refractive index, definition of, 302 , measurement of, 309 Regnault, experiments on Dalton's law, 231 Reg^ult's hygrometer, 241 Resistance, comparison of, 430 — , definition of electrical, 421 — , measurement of battery, 433, 447 STR Resistance, measurement of galvano> meter, 433. 445 — , relation between ten4>erattire and» 4*9. 458 — , work and, 421 — , specific, 429 — , standards <», 421 — boxes, 427 — measured by B.A. wire bridge, 451 ^— of conductors in multiple arc, 433 in series, 422 mercury 426 Resistances compared by Carey Foster's method, 455 Resonance tube, 172 Resonator, 165 Rigidity, 130 Rumfond's photometer, 248 SCALE pans, comparison of weights of, lOI — telescope and mirror, method of ad> justing, 147 Sorew-gauge, 57 Sensitiveness <^ a balance, 91, 97, 99 Sextant, adjustments of, 254 Shearing strain, 139 Shunts, 424 Sine galvanometer, 389, 397 Siren, 168 — , method of using, 170 Solenoidal magnet, 348, 356, 358, 359 , force due to a, 359 Sound, velocity of, 172 ^ Specific gravity, definition of, 103 bottle, 112 of a luiuid, methods of measuring. Ill, 116, 118, 123, 132 of a solid, methods of measuring* 107, too, 112, 116, 117, 121, 163 — heat, aefinition of, 212 , method of cooling,- 225 ^ — of mixttu«, 212 — — of a liquid, ai8 — resbtance, 429 , measurement of, 453 Spectra, comparison of, 301 Spectro-photometer, 344, 341 Spectrometer, 305 — , adjustment of, 306 Spectroscope, 297 — , adjustment of a, 297 Spectrum, mapping a, 297 — , method of ootaining a pure, 396 -, pure, 295 — of electnc spark, 399 Spherometer, 59 Standards office of Board of Trade, 9, 11 Strain, 139 Strengths of absorbing solutions, oxn^ panson of, 344 Stress, X3P String*, vibration of, 175 Index. 487 TAB TABLES, use of, 40 \ Tangent galvanometer, 389, 397 Tap, three-way, 113 Taring, loj Telescope, magnifying powers of, 979, 381 — mirror and scale, method of adjusting, M7 Temperature, definition of, 183 — , measurement of high, 189 — method of measuring, 183, 185 — and resistance, determination of re- lation between, 43^8 Thermometer, air, 208 — , centigrade, 185 — , construction of a, 190 — , corrections of, i&S — , Fahrenheit, 185 — , Kew corrections, 187, x88 — , — standard, 187 — , mercury, 184 — , testing a. 193 — , the weight, aoa — , wet and dry bulb, 238 Thermometry, 183 Time, measurement of, 80 — of oscillation, method of observing, 128 Torsion, determination of modulus of, 146 —, modulus of, 139, 140J 144^ Trig^onometrical approximations, 45 Tuning forks, comparison of pitch of, 165 UNIT of heat, 2X1 — of resistance, British Associa- tion, 436 Units, absolute, 17 — , arbitrary and absolute, 10 — , change of, 24, 98 — , derived, 17 YOU Units, fundamental, 17 — , practical electrical, 22 — , table of arbitrary, 23 — , the C.G.B. system of, 21 VELOCITV of sound, 172 Verniers, 50, 53 Vibration, method of obser\'ing time of complete, 148 — frequency, determination of, 168 — needle. Maxwell's, 146 — numb^, 164 — of string, X7S Volt, practical unit of E.M.F., 419 Voltameter, 406, 408, 410 — as a current meter, 409 — for decomposing water, 411 Volume, measurement of, 78 Volumenometer, 160 WATCH, rating a. 81 Water ; electrical decomposition of, 411 — , ex^nsion of, 192 — equivalent J 215 , determination of, 216 Wave length, measurement of, 315, 319 , by spectrometer, 290 of a high note, 180 Weighing, method of double, loi ; oscillations, 91, 97 Weight thermometer, 202 Weights, 91, 97 Wheatstone Bridge, theory of, 437 YARD standard, 11 Young's modulus, 140, 141 \ W^vv* •'Sfcvv...... ;:iri-/5';;i'^J;;i«:!^iv<:-;U;«r r!!!vv^vvr^ VWVW^ •VWWWw^w *rW»^W§;s:; -•vWV^vWVwWv •^ - ..v^«. •<j*'Vw>^ ^r»* vv^v'*^'' .^^'^^i^i^i^VM%^^yy^^^^ «¥*W^%, y^'WwV^v^ '^^v^^ Wvv* ■Wuv.. ..jrw^. 