None
energy required to produce an ion, 58 secondary radiation produced bj I rays, 187 slow moving ions in air, 528 Larmor radiation theory, 77 radiation of energy from moTing electron, 79 structure of the atom, 157 Lead, radio-active preparation of, 26 radiations from, 26 Le Bon rays from bodies exposed to sunlight. 5 discharging power of quinine sulphate, 9,530 Lenard ionization of gases by ultra-violet light, 9 action of ions on a steam jet, 47 penetrating power of cathode ran, 73 negative charge carried by Lenard rays, 120 absorption of cathode rays propor- tional to density, 136, 137 Lerch, von chemical properties of active deposit of thorium, 313 electrolysis of solution of active de- posit, 313 effect of temperature on excited ac- tivity, 315 temporary activity of active deposit from thorium, 415 Lockyer inorganic evolution, 499 Lodge, Sir Oliver electronic theory, 69 instability of atoms, 487 Lorentz structure of atoms, 157 Lowry and Armstrong radio-activity and phosphoresoence, 444 Luminosity of radium compounds, 205 change of, in radium compounds with time, 205 spectrum of phosphorescent light from radium bromide, 206 of radium compounds unaffected by temperature, 210 Mache radium emanation in hot springs, 513 Mache and von Sohweidler velocity of ions in air, 528 INDEX 671 Makower diffusion of radium emanation, 274 diffusion of thorium emanation, 276 Marckwald preparation of radio-tellurium, 25 rate of decay of radio-tellurium, 411 Mass apparent mass of electron, 71, 127 variation of mass of electron with speed, 127 et seq. of a particle, 147 et seq. Materials radio-activity of ordinary, 528, 536 et seq. Matteucci rate of dissipation of charge in dosed vessels, 531 McClelland absorption of 7 rays, 181 secondary rays from fi and 7 rays from radium, 192 McClung coefficient of recombination of ions, 41 conductivity of gases exposed to X rays, 64 ionizatioil by a rays from radium C, 550 McClung and Bntherford energy required to produce an ion, 58 variation of current with thickness of layer of uranium, 195 estimate of energy radiated from radio- elements, 418 radiation of energy from radium, 438 McLennan absorption of cathode rays, 65 radio-activity of snow, 506 excited radio-activity at Niagara Falls, 519 McLennan and Burton penetrating radiation from the earth, 520 radio-activity of ordinary materials, 537 emanation from ordinary matter, 538 Metabolon definition of, 446 table of metabolons, 449 radio-elements as metabolons, 457 Meteorological conditions effect of, on radio-activity of atmo- sphere, 517 Methods of measurement in radio-activity, 82 et »e<^. comparison of photographic and elec- trical, 83 et $eq. description of electrical, 84 et seq. Meyer and Himstedt production of helium by radium, 479 Meyer and Schweidler magnetic deviation of j3 rays by elec- trical method, 113 absorption of /9 rays of radium by matter, 136 activity proportional to amount of uranium, 195 emanation from uranium, 348 effect of crystallization on activity of uranium, 349 rate of decay of radio-tellurium, 411 Minerals, radio-active constant ratio of radium to uranium, 459 et seq. list of minerals, 461 age of, 485 composition of, 554 et seq. Mobility of ions, 43 et seq. Moisture effect of, on velocity of ions, 43, 45 effect of, on emanating power, 255 Molecule number of, in 1 c.c. of hydrogen, 54 Molecular weight of radium emanation, 273 of thorium emanation, 275 Nagel and Himstedt action of radium rays on the eye, 217 Niewenglowski rays from sulphide of calcium, 4 Nomenclature of successive products, 328 et seq. Number of molecules per c.c. of hydrogen, 54 of ions produced in gas by active sub- stances, 55 of /? particles expelled from 1 gram of radium, 124 of a particles emitted per gram of radium, 155 of ions produced per c.c. in closed vessels, 534 Occlusion of emanation in thorium and radium, 258 of radium emanation by solids, 310 Owens saturation current affected by dust, 42 penetrating power of rays independent of compound, 164 absorption of a rays varies directly as the pressure of gas, 169 effect of air currents on conductivity produced by thorium, 238 Oxygen change into ozone, by radium rays, 213 572 INDEX Oxygen (cont.) production of, from radium solations, 215 Ozone production of, by radium rays, 213 Paraffin objection to, as an insulator, 96 conductivity of, under radium rays, 210 Pascben distribution of velocity amongst /3 particles, 131 et seq. absence of magnetic deflection of y rays, 183 y rays and electrons, 185 heating effect of y rays, 186, 429 Patterson number of ions per c.c. in closed vessel, 534 natural conductivity of air due to an easily absorbed radiation, 536 effect of temperature on natural con- ductivity of air, 536 Peck and Willows action of radium rays on spark, 208 Pegram electrolysis of thorium solutions, 314 temporary activity of substances sepa- rated &om thorium, 415 Penetrating power comparison of, for a, B and y i-ays, 111 variation in, of /3 rays, 134 et seq. variation of, with density for fi rays, 137 comparison of, for a rays from radio- elements, 164 variation of, with density for a rays, 169 variation of, with density for y rays, 182 Penetrating radiation from the earth and atmosphere, 520 Perrin charge carried by cathode rays, 73 theory of radio-activity, 437 Phosphorescence production of, by radium, 19 production of, by radium and polo- nium rays, 201 et seq. comparison of, produced by a and ^ rays, 202 of zinc sulphide, 202 of barium platino-oyanide, 203 of willemite and kunzite, 203 produced by radium emanation in sub- stances, 203, 252 diminution of, with time, 205 of radium compounds, 205 Phosphorescence {cont.) spectrum of phosphorescent light of radium bromide, 205 spectrum of phosphorescent light of '^emanium,** 206 production of by heat (thermo-lumin- escence), 207 use of, to illustrate oondensation of emanations, 279 connection of with ionization, 547 et seq. Phosphorus action of radium rays on, 214 ionization produced by, 529 Photo-electric action produced by radium rays in certain substances, 214 Photographic method, advantages and disadvant- ages of, 83 relative photographic action of rays, 83 connection of photographic action with ionization, 546 Physical action of radium rays on sparks, 208 on electrodeless discharge, 208 on selenium, 208 on conductivity of insulators, 209 Physiological action of radium rays production of bums, 216 effect on bacteria, 216 effect on eye, 217 Piezo-^lectrique of quartz description of, 105 Pitchblendes comparison of radio-activity of, 11 radio-elements separated from, 13 it seq. radium continually produced from, 459 constitution of, 557 Polarization of uranium rays absence of, 7 Polonium methods of separation of, 22 rays from, 23 decay of activity of, 23 discussion of nature of, 24 similarity to radio-tellurium, 26 magnetic deviation of a rays from, 146, 150 slow moving electrons, 153 increase of absorption with thickness of matter traversed, 163 connection of, with radium F, 411 Potential required to produce saturation, 32 et seq. fall of potential needed to produce ions at each collision, 58 INDBX 573 Potential (cont.) gradient due to movement of ions, 65 Precht and Range spectnim of radium, 17 atomic weight of radium, 18 heating effect of radium, 420 PreBRure effect of, on velocity of ions, 46 effect of, on current through gases, 61 et $eq. production of emanation independent of, 265 effect of, on distribution of excited activity, 317 effect of, on natural conductivity of air in closed vessels, 534 Products, radio-active list of, from radio-elements, 449 properties of, 449 amount of in radium, 452 et teq, radiations from, 455 Quartz piezo-^lectrique use of, in measurement of current, 105 Quinine sulphate discharging power of, 530 phosphorescence of, 530 Badiations emitted hy uranium, 8 emitted by thorium, 10 emitted by radium, 18 emitted by actinium, 21 emitted by polonium, 23 method of measurement of, 82 et )fi'q. methoilfl of comparison of, 108 three kindu of, 109 analogy to rays from a Crookes tube, no relative ionizing and penetrating power of. 111 ditHoulticR of comparative measure- ment of. 112 /9 ravH, 113 a rays, 141 7 r.iyfl, 179 secondary rays, 187 coniparison of ionization of a and /3 ravH, 194 phosphorescent effect of, 201 et teq. pliysical actions of, 207 et seq. chemical actions of, 213 et seq, physiological actions of, 216 from the emanation, 263 fn»m C-r X, 347 connt^tion of, with heat emission, 421 et teq. from different active prodnoti, 455 Badiations (cont.) conservation of energy of each specific type of, 469 et seq. Radio-lead connection of, with polonium, 411 et seq, connection of, with radium D, 413 Radio-tellurium rate of decay of, 411 connection of with radium F, 411 Radium discovery of, 13 separation of, 13 spectrum of, 16 atomic weight of, 17 radiations from, 18 compounds of, 19 nature of radiations from, 109 /? rays from, 113 a rays from, 141 7 rays from, 179 secondary rays from, 187 production of phosphorescence by, 201 et seq, spectrum of phosphorescent light of, 206 physical actions of, 207 et seq, chemical actions of, 213 et seq, physiological actions of, 216 emanation from, 246 properties of emanation from, 247 et seq. chemical nature of emanation from, 267 diffusion of emanation from, 269 condensation of emanation from, 277 amount of emanation from, 288 volume of emanation from, 289 spectrum of emanation from, 21)2 excited radio-activity from, 295 et seq. decay of excited activity from, 806 et seq. difference in properties of radium and the emanation, 327 nomenclature of products, 328 theory of successive changes in, 380 alteration of activity of, by removal of emanation, 371 et seq. recovery of activity of, after removal of emanation, 372 effect of escape of emanation on re- covery of activity of, 374 non-separable activity of, 375 period and properties of radium A, B and C, 376 et seq. analysis of active deposit of rapid changes of radium, 377 analysis of /9 ray curves, 381 et seq, analysis of a ray curves, 386 et seq, equations of activity carves, 389 674 INDEX Badiam {cont,) efifeot of temperature on active de- posit of, 390 relative activity due to products of, 895 active deposit of slow transformation, 397 physical and chemical properties of radium D, E and F, 398 et seq. effect of temperature on active de- posit of slow change, 401 separation of radium F by bismuth, 402 products of, 402 et seq. rate of transformation of radium D, 404 et seq. variation of the activity of the active deposit over long periods of time, 407 amounts of radium D, E and F in old radium, 408 variation of activity of, with time, 409 products of in pitchblende, 410 origin of radio-tellurium, 411 origin of polonium, 411, 412 origin of radio-lead, 418 temporary activity of inactive matter separated from pitchblende, 416 et seq. heat emission of, 419 et seq. heat emission of emanation from, 420, 431 heating effects due to products of, 483 theories of radio-activity of, 437 et seq. discussion of theories of radio-activity of, 441 et seq. energy of radiations, not derived from external source, 442 et seq. theory of radio-active change, 444 et seq. list of active products of, 449 amount of products of, 452 rate of change of, 457 life of radium, 467 origin of, 469 et seq. production of, by uranium, 459 et seq. amount of in 1 gram of uranium, 461 amount of, in minerals, 461 radio-activity of, independent of con- centration, 466 et seq. disappearance of, 467 life of, independent of concentration, 468 conservation of radio-activity of, 469 et seq. loss of weight of, 473 experiments to determine loss of weight of, 474 Badium (eont.) total emission of energy from 1 gnm of, 474 et seq. production of helium from, 476 helium, disintegration prodnet of, 479 et seq. amount of helium from, 480 possible causes of disintegration d^ 486 et seq. amount of, to account for heat of sun, 491 possible connection of with heat of sun, 491 possible connection of with beat of earth, 493 probable amount of, in earth, 495 amount of, in atmosphere, 496, 584 presence of, in atmosphere, 521 et seq. Baidium A decay curve of, 878 radiation from, 381 effect of, on activity curves, 386 etseq. connection with later changes, 392 activity supplied by, 393 Badium B absence of rays in, 881 effect of, on activity curves, 381 et seq. effect of temperature on, 390 volatiUty of, 390 absence of heating effect of, 433 nature of rayless change in, 454, 5o2 Badium C radiations from, 381 analysis of /3 ray curves of, 381 et seq. analysis of a ray curves of, 386 et seq. effect of temperature on, 390 activity supplied by, 394 et seq. heating effect of, 426 use of, as a source of /9 rays, 436 explosive nature of change in, 456 magnetic deflection of rays from, 643 velocity and value of elm for rays from, 544 Badium D origin of name of, 376 connection of, with active deposit, 403 period of transformation of, 406 effect of, on variation of activity, 407 presence in old radium, 408 effect of, on activity of old radium, 409 presence in pitchblende, 410 connection with radio-lead, 413 amount of, in 1 ton of uranium, 454 Badium E effect of temperature on, 401 connection of, with /? ray activity of active deposit, 403, 400 INDEX 575 Badiam E (eont.) connection with radio-leftd, 413 Badium F variation of activity due to, 398 effect of temperatare on, 401 separation of, on bismuth plate, 402 connection with active deposit, 403 variation of activity of, over long periods of time, 407 presence in old radium, 409 effect of, on activity of old radium, 409 presence in pitchblende, 410 connection with radio- telloriam, 411 connection with polonium, 411, 412 connection with radio-lead, 413 Rain radio-activity of, 505 decay of activity of, 606 Bamsay, Sir W. amount of helium in thorianite, 486 Bam Kay and Collie spectrum of emanation, 292 Banisay and Cooke radio-activity produced by radiation from radium, 472 Bamsay and Soddy evolution of gas from radium, 215 production of hydrogen and oxygen from radium, 215 chemical nature of the emanation, 268 gaaeouH nature of the emanation, 268 volume of emanation, and change with time, 289 helium from radium emanation, 291 amount of helium produced by ra- dium, 480 Bamsay and Travers amount of helium in fergusonite, 486 Bayless changes discussion of, 454, 552 Be, F. theory of radio-activity, 441 Becombination of ions, 40 et $eq, constant of, 42 Becovery of activitv of thorium after removal of Th X, 221 of activitv of uranium after removal of Ur X, 223 signiticance of law of, 224 effect of conditions on rate of, 232 of activity of radium after removal of emanation, 872 of heating effect of radium, 423 Beflection no evidence of direct reflection for uranium rays, 7 Beflection (cont.) diffuse reflection of rays, 7 Befraction no evidence of, for uranium rays, 7 Begeneration of emanating power, 256 Bicharz and von Helmholtz action of ions on steam jet, 47 Bicharz and Schenck theory of radio-activity, 441 Bossignol and Gimingham decay of thorium emanation, 242 Bunge spectrum of radium, 17 Bunge and Bodlander evolution of gas from radium, 215 Bunge and Precht spectrum of radium, 17 atomic weight of radium, 18 heating effect of radium, 420 Bussel photographic action of substances, 88 Saake amount of emanation in air at high altitudes, 519 Salomonsen and Dreyer coloration of quartz by radium rays, 213 Saturation current meaning of, 33 et »eq. application of, to measurements of radio-activity, 84 measurement of, 100 et uq, Schenck radium emanation in springs, 513 Schenck and Bicharz theory of radio-activity, 441 Schmidt discovery of radio-activity of thorium, 10 Schmidt and Wiedemann thermo-luminescence, 207 Schuster number of ions per c.c. in air of Manchester, 528 radio-activity of matter, 529 Schweidlor and Mache velocity of ions in air, 528 Schweidler and Meyer magnetic deviation of /3 rays by electrical method, 113 absorption of /3 rays of radium by matter, 136 activity proportional to amount of uranium, 195 emanation from uranium, 348 effect of crystallization on activity of uranium, 349 rate of decay of radio- tellurium, 411 576 INDEX Scintillations discovery of, in zinc sulphide screen, 158 connection of, with a rays, 158 illastration of, by spinthariscope, 158 caase of, 160 production of, by action of electric field, 160 Searle apparent mass of moving charged body, 71. 127 Secondary rays examination of, by photographic method, 187 examination of, by electrical method, 188 production of, by /3 and 7 rays, 189 et $eq. from different materials, 191 amount of, depends upon atomic weight, 192 magnetic deflection of, 193 Seitz absorption of electrons by matter, 137 et aeq. Selenium action of radium rays on, 208 Simon value of e/m for cathode rays, 75, 129 Simpson amount of excited activity in north of Norway, 519 Slater, Miss effect of temperature on active de- posit of thorium, 854 Smolan, Beattie and Kelvin discharging power of uranium rays, 7 Snow radio-activity of, 506 decay of activity of, 507 Soddy comparison of photographic and elec- trical action of uranium rays, 83 nature of rays from Ur X, 347 production of radium from uranium, 463 Soddy and Bamsay evolution of gas from radium, 215 production of hydrogen and oxygen from radium, 215 chemical nature of the emanation, 268 gaseous nature of the emanation, 268 volume of the emanation, and change with time, 289 helium from radium emanation, 291 amount of helium produced by ra- dium, 480 Soddy and Butherford separation of Th X, 220 Soddy and Butherford (con<.) decay of activity of Th X, 381 recovery of activity of thorium freed from Th X, 221 decay of activity of Ur X, 223 recovery of activity of uranium freed from Ur X, 223 explanation of decay and recoToy curves, 224 rate of production of Th X, 827 theory of decay of activity, 289 influence of conditions on rate of decay and recovery of activity, 2SS disintegration h3rpothe8iB, 234 decay of activity of radium emans* tion, 247 measurements of emanating power, 254 effect of temperature, moisture, and solution, on emanating power, 255 regeneration of emanating power, 256 constant rate of production of emani* tion of radium and thorium, 257 source of thorium emanation, 261 radiations from the emanation, 264 chemical nature of emanation, 267 condensation of emanations of radium and thorium, 277 temperature of condensation of ems* nation, 278 effect of successive precipitations on activity of thorium, 358 recovery of activity of radium, 372 theory of radio-activity, 439 theory of radio-active change, 445 conservation of radio-activity, 469 Soil radio-activity of, 507 et teq. difference in activity of, 508 et teq. Solution coloration of, by radium, 15 of active deposit in acids, 312 electrolysis of active, 313 Source of thorium emanation, 261 of radium and actiuium emanations, 263 Spark action of radium rays on, 208 Spectrum spark spectrum of radium, 15, 16 flame spectrum of radium, 17 effect of a magnetic field on spectrum of radium, 17 of polonium, 23 of phosphorescent light of radium bromide, 206 of emanation, 292 of helium in radium gases and emana- tion, 477 iin)Ex 577 Spinthariscope description of, 158 Springs emanation from water of, 51S Stark energy to produce an ion, 58 Stoney, Johnstone nse of term electron, 76 Strauss and Hofmann radio-active lead, 27 Strott conductivity of gases for radiation, 63, 64 conductivity of gases produced by y rays, 64, 183 negative charge carried by /3 rays, 122 et seq, absorption of /3 rays proportional to density, 136 nature of a rays, 142 attempt to measure charge of a rays, 153 constant ratio of uranium to radium in minerals, 462 connection of thorium with helium, 483 absorption of radium rays from sun by atmosphere, 492 presence of radium in Bath waters, 513 radio-aotivity of ordinary matter, 536 Sun effect of radium in, 491 age of, 492 Temperature effect of, on intensity of radiations from uranium and radium, 210 effect of, on luminosity, 210 rate of decay of radium emanation unaffected by, 249 of condensation of emanations, 283 rate of decay of thorium emanation unaffected by, 287 effect of, on excited activity, 315 effect of, on active deposit of thorium, 354 effect of, on active deposit of ac- tinium, 368 effect of, on active deposit of rapid change of radium, 390 effect of, on active deposit of slow change, 401 of radium above surrounding space, 419 effect of, on amount of excited ac- tivity in atmosphere, 518 effect of, on natural ionization of air, 536 Theories of radio-activity, review of, 437 et 8eq, discussion of, 441 et ieq. disintegration theory, 445 et seq, Thermo-luminescence, 207 Thomson, J. J. relation between current and voltage for ionized gases, 34 difference between ions as conden- sation nuclei, 49 charge on ion, 50 magnetic field produced by an ion in motion, 69 apparent mass of electron, 71 action of magnetic field on moving ion, 72 determination of e/m for cathode stream, 73 origin of X rays, 80 slow velocity electrons from radio- tellurium, 153 charge carried by a rays, 154 theory of radio-activity, 440 cause of heat emi8sio^ from radium, 442 structure of atom, 487 possible causes of disintegration of radium, 487 nature of electrons, 496 emanation from tap-water and deep wells, 510 radio-activity of ordinary materials, 539 Thomson, J. J. and Rutherford ionization theory of gases, 31 et seq. Thorium discovery of radio-activity of, 10 emanation from, 11 preparation of non-radio-active tho- rium, 29 nature of radiations from, 109 /3 rays from, 114 a rays from, 141 7 rays from, 180 separation of Th X from, 220 recovery of activity of, 221 disintegration of, 234 emanation from, 238 properties of emanation from, 239 diffusion of emanation from, 275 condensation of emanation from, 277 excited radio-activity from, 295 et seq, analysis of active deposit of, 3al et seq. rayless change in, 352 explanation of initial portion of decay curve, 358 explanation of initial portion of re- covery curve, 368 578 INDEX Thorium {cont.) effect of saccessive precipitations on, 358 recovery curve after large number of precipitations, 359 products of, 363 non-separable activity of, 363 radiations from active products of, 363 division of activity amongst active products of, 363 rate of emission of energy by, 432 theories of radio-activity of, 438 discussion of theories of radio-ac- tivity, 441 et seq. source of energy of radiations, 442 et seq. theory of radio-active change, 444 et seq. table of radio-active products of, 419 rate of change of, 458 life of, 458 conservation of radio-activity of, 469 total emission of energy from 1 gram of, 475 possible causes of disintegration of, 486 et »eq. Thorium A period and properties of, 352 et seq, absence of rays in, 352 effect of temperature on, 354 Thorium B period and properties of, 352 et seq. effect of temperature on, 354 radiations from, 363 Thorium X methods of separation of, 220 law of decay of activity of, 221 law of recovery of activity of, 221 theory to explain production of, 224 material nature of, 226 continuous production of, 227 explanation of decay of activity of, 229 effect of conditions on the rate of change of, 233 disintegration hypothesis to explain production of, 234 minute amount of, produced, 237 effect of successive separations of, on activity of thorium, 358 et seq. analysis of decay and recovery curves of, 358 radiations from, 363 Tommasina scintillations produced by electrifica- tion, 160 Townsend ions by coUision, 39, 57 coefficient of recombination, 41 Townsend (cont.) diffusion of ions, 51 et seq, comparison of charge on ion with that on hydrogen atom in electro- lysis, 53 number of molecules per c.c. of gas, 54 ionization by collision for different speeds, 171 Transformations, successive theory of, 325 et seq. nomenclature of, 328 activity due to, 337 detection of a rayless change in, 341 in uranium, 346 et seq. in thorium, 351 et seq. in actinium, 364 et seq, in radium, 371 et seq, list of, 449 origin of radium in, 459 helium, a result of, 476 et seq. possible cause of, 486 et seq, application of, to evolution of matter, 497 et seq. Transmission of excited radio-activity of radium and thorium, 318 et seq. of excited radio-activity of actinium, 323 Travers and Bamsay amount of helium in fergusonite, 486 Troost rays from hexagonal blende, 4 Uranium discovery of radio-activity of. 5 persistence of radiations of, 6 discharging power of rays, 7 absence of reflection, refraction and polarization, 7 examination of uranium minerals, U et seq. relative activity of compounds of uranium, 12 nature of radiations from, 109 )8 rays from, 114 a rays from, 141 7 rays from, 180 separation of Ur X from, 219 recovery of activity of, 219 changes in, 346 et seq. uon- separable activity of, 347 radiations from Ur X, 347 et seq. method of measurement of activity of Ur X, 347 emission of energy by, 418 theories of radio-activity of, 437 (^ seq. discussion of theories of radio-activ- ity, 441 et seq. INDEX 579 Uranium {cont.) soarce of energy of radiation, 442 et aeq, theory of radio-active change, 444 et 9fq, table of active prodacts, 449 rate of change of, 458 life of, 458 radium probable prodnct of, 459 et seq. amount of radium in, 460 et seq, amount of, in radio-active minerals, 461 growth of radium in, 463 conservation of radio-activity of, 469 total emission of energy from 1 gram of, 475 poKsible causes of disintegration of, 486 et $eq. Uranium X separation of, by Crookes, 219 reparation of, by Becquerel, 219 decay of activity of, 223 recovery of activity of, 223 theory to explain production of, 224 et »eq. material nature of, 226 explanation of decay of activity of, 229 changes in, 346 et *eq, radiations from, 847 et $eq, method of measurement of radiations from, 347 effect of crystallization on activity of, 349 ditfuRion of, 350 Velocity of ions in electric field, 42 et seq. difference between, of positive and negative ions, 43 et aeq, of ^ particle or electron, 126 et seq. variation of mass of electron with, 127 of a particle, 148 of transmission of carriers of excited activity, 320 et aeq. of ions in atmosphere, 528 Villard discovery of y rays from radium, 179 alteration of X ray screen with time, 205 activity produced by cathode rays, 530 Vinc«'nti and Levi Da Zara radiimi emanation in spring waters, 516 Voller variation of activity of radium with concentration, 467 Volume of radium emanation, calculation of, 289 decrease of, of radium emanation, 290 Walker, G. W. theory of electrometer, 90 Walkhoff action of radium rays on skin, 216 Wallstabe diffusion of radium emanation into liquids, 276 Water emanation from, 510 et teq. decay of activity of emanation from, 511 ft seq. Water-falls amount of excited activity produced at Niagara, 520 electrification produced near, 520 Watts, Marshall atomic weight of radium, 18 Weichert velocity of cathode rays, 76 Weight loss of by radio-elements, 473 attempts to measure loss of in radium, 474 Wheeler and Bumstead diffusion of radium emanation, 273 emanation from surface water and the soil, 512, 522 identity of emanation from soil with radium emanation, 512, 522 Whetham effect of valency of ion on colloidal solutions, 215 production of radium from uranium, 463 Wiedemann thermo-luminescence, 207 Wiedemann and Schmidt thermo-luminescence, 207 Wien value of ejm for canal rays, 78 positive charge of canal rays, 78 amount of charge carried by /3 rays, 124 Willcock, Miss and Hardy coloration of iodoform solution by radium rays, 214 ^UUemite V^hosphorescence of, under radium rays, 203 use of, to show condensation of emana- tion, 279 Willows and Peck action of radium rays on spark, 208 580 INDEX Wilson, C. T. R. ions as iwoiei of condensation, 47 et seq, difference between positive and nega- tive ions as condensation nuclei, 49 equality of charges carried by positive and negative ions, 50 construction of electroscope, 86, 88 natural ionization of air in vessels, 601 radio-activity of rain and snow, 505, 506 loss of charge in closed vessels, 531 et seq., 534 presence of ions in dust-free air shown by condensation, 533 number of ions produced per c.c, 533 effect of pressure and nature of gas on ionization in sealed vessels, 534 Wilson, H. A. charge on ion, 51 Wilson, W. E. radium in sun, 491 Wdlfl, Hofmann and Gk)nder properties of radio-active lead, 27, 413 Wood, A. radio-activity of ordinary materialst 540 Zara, Levi Da and Yincenti radium emanation in spring waters, 516 Zeeman action of magnetic field on light, 77 Zeleny velocity of ions, 42 et seq, difference of velocity of ions, 45 potential gradient between electrodes, 65 Zerban and Hofmann connection of activity of thorium with uranium, 29 Zinc Sulphide scintillations produced in by a rays, 158 cause of luminosity of, 160, 549 u CAMBBIDOE: printed by JOHN clay, M.A. at the UNIVEB8ITY PBESS. e I \ If i. 