None
Thorium B. A 212; P 10-6 hrs; L 15'3 hrs; X -0654 hr; ft rays, /x. 110, groups ft -63, '72; analogous in chemical properties to radium B. {Th. Cj. A 212 ; P 60 mins ; L 84*6 mins ; X -01 18 min. ; a + ft rays; R 4*80 ; ft rays ^ 15'6; y rays weak; analogous in chemical properties to radium C. Th. C2. A 212 ; P very short ? ; a rays, 72 8 '60. Thorium D. A 208; P 3'1 mins; L 4'47 mins; X '224 min.; ft + y rays; /? rays /x 24-8, for thorium C + D /x 18-8, groups for Th. C + D, /3 -29, -36, -93— -95; y rays /^ -46 ; separated by recoil from thorium C; possibly transformed into bismuth. INDEX The numbers refer to the pages a rays nature of, 9 difficulty of saturation with, 32 trails of, by condensation method, 49 total ionisation by, in different gases, 65 €lectroscope for measurement of, 90 use of, for ionisation standards, 111 general properties of, 114 et seq. discovery of, 118 magnetic and electric deflection of, 120 magnetic and electric deflection of homogeneous, 123 et seq. •counting of, by electrical methods, 128 et seq. •counting of, by scintillations, 133 detection of, by condensation method, 134 charge carried by, 135 chemical nature of, 137 connection of, with helium, 139, 556 retardation of, 141 photographic effect of, from thick layers, 143 absorption of, 146 ionisation curves for pencils of, 148 ionisation due to one a particle, 153 ionisation curves for, in different gases, 155 explanation of the ionisation curve for, 156 energy required to produce an ion by, 158 decrease of ionisation with distance for, 159 range of, 161 stopping power of, in different sub- stances, 165 secondary radiations from, 170 delta rays from, 170 recoil radiation from, 170, 174, 401 nature of recoil radiation from, 174 a rays (cont.) ionisation due to recoil atom from, 179 scattering of, 180 theory of scattering of, in thin films, 184 probability variations in emission of, 186 double scintillations from, 191 phosphorescence produced by, 296 et seq. scintillations in zinc sulphide by, 297 effect of continued bombardment of, on zinc sulphide, 300 luminosity in gases produced by, 302 photographic effect of, 305 effect of, in producing halos, 309 distribution of, from thin films, 312 decomposition of water by, 317 possible transformation of matter by, 320 complex nature of, from uranium, 448 decay of active deposit of radium measured by, 487 et seq. complex nature of, from thorium C, 539 connection of, with production of helium, 556 et seq. connection of, with heat emission, 571 heating effect of, 577 change of valencv due to expulsion of, 606 relation between range of, and period of transformation, 607 possible origin of, 621 connection of, with aurora, 654 photograph of trails of, 663 photographic record of, 664 Abraham electrical mass of charged particle, 71 Absorption of a rays by solids and gases, 146 theory of, by matter, 148 672 INDEX Absorption of ft rays exponential law of, 211, 223 effect of conditions on measurement of, 224 table of coefficients of, for ft rays from different products, 225 connection of, for ft rays with chemical constitution, 226 from uranium X by elements, 226, 233 by liquids, 228 by radio-active matter, 229 from radium by air, 229 theories of, 230 of homogeneous, 234 variation of, with speed, 238 Absorption of emanations by liquids, 375 by solids and charcoal, 378 Absorption of y rays from radium, 258 variation of, with conditions, 261 connection of, with density, 263 by gases, 266 table of, for radio-active products, 267 variation of, with temperature, 293 Actinium discovery of, 18 et seq. emanation from, 19 connection with emanium, 19, 519 spectrum of luminosity of, 304 activity of, in uranium minerals, 447 history of discovery of, 519 chemical properties of, 520 period of, 521 radiations from, 521 connection of, with uranium series, 521 origin of, as branch product, 522 analysis of active deposit of, 523 series of transformations of, 533 relation between range of a rays and period of transformation for pro- ducts of, 607 Actinium A discovery and properties of, 396, 523 Actinium B period and properties of, 524 volatilisation of, 526 radiations from, 532 electro-chemical properties of, 603 Actinium C separation and properties of, 525 period of, 526 volatilisation of, 526 possible complexity of, 532 electro-chemical properties of, 603 Actinium D separation and properties of, 527 volatility of, 527 Actinium D (cont.) radiations from, 532 electro-chemical properties of, 603 Actinium emanation rapid emission of, 19 decay of, 351 effect of conditions on escape of, 359 temperature of condensation of, 371 absorption of, by liquids, 377 absorption of, by charcoal, 380 diffusion of, 387 number of a particles expelled by, 395 transformation of, 524 Adams range of a particles in gases, 166 presence of radium emanation in tap- water, 641 Adams and Eve effect of pressure on 7 ray activity of radium, 505 Age of radio-active minerals, 562, 598 of geological strata, 566 of earth, 644, 653 of sun, 655 Allen (S. J.) compensation method of measure- ment, 103 absorption of ft rays by liquids, 228 velocity of 8 rays excited by 7 rays, 274 thorium emanation in atmosphere, 626 activity of snow, 627 Allen (S. J.) and Eutherford active matter in the atmosphere, 625 Allen (H. S.) and Blythswood (Lord) radium emanation in hot springs, 641 Angerer on the energy of ft rays excited by X rays, 288 Angstrom heating effect of radium, 570 Antonoff properties of uranium Y, 454 period of radium D, 513 period of radium E, 514 Armstrong and Lowry theory of radio-activity, 413 Aschkinass charge carried by a rays, 156 Ashman amount of radium emanation i» atmosphere, 633 Atmosphere discovery of active matter in, 624 theory of collection of active matter in, 627 effect of meteorological conditions on» active matter in, 629 INDEX 673 Atmosphere (cont. discovery of, 193 magnetic deflection of, by photo- graphic method, 194 complexity of, 196 magnetic deflection of, by electric method, 197 charge carried by, 198 determination of ejm and variation with speed for, 204 passage of, through matter, 209 scattered or reflected, 212 scattering of transmitted, 218 scattering of, by thin sheets of matter, 219 absorption of, 223 connection of absorption of, with chemical constitution, 226 absorption of, by air, 229 total ionisation produced by, 230, 579 theories of absorption of, 230 absorption of homogeneous, 234 variation of absorption of, with speed, 238 retardation of, in traversing matter, 240 variation of ionisation with velocity of, 245 distribution of velocity of, in radium, 250 emission of homogeneous groups of, 252 connection of 7 rays with, 270 excited by 7 rays, 271 incidence and emergence B rays excited by 7 rays, 273 variation of amount of, excited with material, 274, 278 production of 7 rays by, 282 origin of energy of, from 7 rays, 288 R. R.-A. )3 rays (cont.) phosphorescence produced by, 296 et seq. decay of luminosity produced by, 301 photographic effect of, 305 distribution of, from uranium, 313 decomposition of water by, 319 decay of active deposit of radium measured by, 493 variation of distribution of, with tem- perature, 504 heating effect of, from radium, 578 origin of, in transformations, 610 relation between groups of, from radium, 613 transformation of energy of, into 7 rays, 613 connection of, with aurora, 654 photographs of trails of, 664 v. Baeyer retardation of /3 rays, 244 v. Baeyer, Hahn and Meitner homogeneous groups of 8 rays, 212, 252 velocity of 8 rays from radium, 474 Balance methods of measuring ionisation currents, 103 of comparing quantities of radium, 658 Barium platinocyanide luminosity of, 298, 299 Barkla characteristic Eontgen rays, 85, 291 absorption of characteristic radia- tions, 611 Barnes and Eutherford heating effect of radium and its pro- ducts, 572 heating effect of a, /3 and 7 rays, 578 Barratt ranges of a particles from thorium emanation, 164, 535 Barratt and Marsden probability distribution of a particles, 190 absence of doubles in scintillations from uranium, 448 analysis of a radiations from thorium C, 539 Bary phosphorescence produced by radium rays, 297 Baskerville and Kunz phosphorescence produced by radium rays, 299 Bateman theory of successive changes, 418, 422 43 674 INDEX Bateman, Geiger and Kutherford probability variations of a particles, 188 Beattie, E. theory of electrometer, 97 Beattie, Kelvin (Lord) and Smolan discharging action of uranium rays, 9 Becker conductivity of dielectrics under ra- dium rays, 326 Becquerel, H. discovery of photographic effect of uranium, 7 phosphorescence of uranium salts, 7 discharging action of uranium, 8 reflection, refraction, and polarisa- tion of uranium rays, 9 radiations, types of, from uranium, 9 magnetic deflection of a rays, 122 curvature of a rays in magnetic field, 144 magnetic deflection of /3 rays, 193 complexity of /3 rays from radium, 196 deflection of /3 rays in electric field, 204 discovery of 7 rays, 257 phosphorescence produced by radium rays, 296 luminosity of crystals of uranium nitrate, 302 action of radium rays on phosphorus, 315 conductivity of dielectrics under ra- dium rays, 326 separation of uranium X, 331, 454 structure of the atom, 410 Beilby phosphorescence produced by /3 and 7 rays, 299 Bemont (G.), M. and Mme Curie discovery of radium, 15 Bergwitz decomposition of water by polonium, 318 Berry separation of uranium X by barium, 454 Berthelot effect of radium rays on quartz, 308 Beryl origin of helium in, 565 Bestelmeyer determination of ejm for cathode rays, 208 Bialobjesky conductivity of hydrocarbons under radium rays, 326 Birkeland theory of aurora, 654 Bismuth separation of polonium with, 20 deposit of polonium on, 21 possible end product of thorium, 599 Blanc thorium emanation in atmosphere. 626 active sediment containing thorium products, 642 amount of thorium in rocks, 649 Blanquies (Mdlle) complex nature of actinium C, 532 Blythswood (Lord) and Allen (H. S.) radium emanation in hot springs, 641 Bohm-Wendt and v. Schweidler conductivity of oils under radium rays, 326 Boiling point of radium emanation, 483 Boltwood discovery of ionium, 21, 456 range of a particles from ionium, 162 activity of uranium minerals, 446 relative proportion of uranium and ionium, 457 activity of ionium, 458 life of radium, 459 constancy of radium-uranium ratio in minerals, 460 production of radium by uranium, 465 properties of actinium, 520 activity of actinium in uranium minerals, 521 activity of thorium minerals, 546 separation of meso-thorium, 547 amount of helium in minerals, 564 lead as end product of radium, 597 amount of lead in uranium minerals, 597 radium emanation in thermal springs, 641 method of measurement of amount of radium emanation in water, 642 estimation of small quantities of radium, 660 Boltwood and Eutherford amount of radium in uranium mine- rals, 16, 462 action of emanation on paraffin, 315 rate of production of helium by ra- dium, 557 production of helium by polonium and ionium, 560 Boyle effect of surface condensation of emanations, 373 vapour pressure of radium emana- tion, 374 INDEX 675 Boyle (cont.) absorption of radium emanation by liquids, 376 absorption of thorium emanation by charcoal, 379 Bragg total ionisation by a particles in different gases, 64 corpuscular theory of X rays, 84 emission of a rays, 123 curvature of a rays in magnetic field, 144 theory of absorption of a rays, 147 determination of range of a rays from uranium and thorium, 162 stopping power of combination of two plates, 168 011 the range of /3 particles, 230 incidence and emergence (3 radiation, 275 variation of y ray ionisation with material of electroscope, 278 corpuscular theory of y rays, 289 origin of ionisation by X rays, 293 Bragg and Cooke ionisation curve for a rays in dif- ferent gases, 167 Bragg and Kleeman difficulty of saturation with a rays, 33 absorption of a rays, 147 measurement of ranges of a particle in different substances, 165 Bragg and Madsen variation of emergence /3 radiation with atomic weight, 275 Bronson construction of radio-active resist- ance, 102 decay of thorium emanation, 351 number of a particles from emana- tions, 395, 539 effect of temperature on decay of active deposit of radium, 488 decay of a ray activity of active deposit of radium, 490 effect of temperature on decay of products of radium, 503 period of actinium B, 525 analysis of active deposit of acti- nium, 525 Bronson and Wellisch charge on active deposit, 399 Brooks (Miss) apparent volatilisation of radium B, 175 decay of active deposit of radium, 492 analysis of active deposit of actinium, 525 separation of actinium C by electro- lysis, 526 Brooks (Miss) and Eutherford absorption of a rays, 146 diffusion of radium emanation, 383 decay of active deposit of radium, 487 active deposit of thorium, 536 Bucherer variation of mass of electron with speed, 71, 207 Biichner activity of potassium, 588 amount of radium in rocks, 646 Bumstead emission of delta rays, 173 energy of f3 rays excited by X rays, 288 radium and thorium emanation in atmosphere, 626, 641 Bumstead and Wheeler decay of radium emanation, 352 diffusion of radium emanation, 385 Burton presence of radium emanation in petroleum, 642 Burton and McLennan radio-activity of ordinary materials, 593 penetrating y rays in atmosphere, 594, 634 Callendar method of measuring small heating effects, 585 Cameron and Eamsay decomposition of gases by a rays, 316 rate of decomposition of water by radium, 318 transformation of matter by a rays, 320 volume of radium emanation, 480 spectrum of radium emanation, 482 Campbell (N. Cathode ray discovery and properties of, 76 et seq. Cermak and Schmidt (H. W.) effect of temperature on decay of products of radium, 503 Chadwick absorption of y rays by gases, 265 production of y rays by /3 rays, 282 Chadwick and Eutherford 7 ray activity of emanation, 498 balance method of comparing radium standards, 658 Changes (see Transformations) Characteristic radiations of elements, 85, 611 Charge carried by an ion, 50 et seq. value of, used for calculation, 53 carried by a particle, 135 carried by /3 rays, 198 carried by /3 rays from radium B and C, 202 et seq. nature and origin of, carried by active deposit, 399 Chaumont diffusion of radium emanation, 384 Chemical action produced by a, /3 and y rays, 314 et seq. produced on water by a, /3 and y rays, 317 amount of, in water, 319 Chemistry of radio-active bodies, 600 et seq. Cheveneau and P. Curie magnetic properties of radium, 474 Child potential gradient, 67 variation of current with voltage for surface ionisation, 67 Classen determination of ejm for cathode rays, 208 Clock radium, 199 Clouds formation of, by condensation of water round ions, 46 et seq. Collie and Eamsay spectrum of radium emanation, 482 Collision ionisation by, 36 et seq. detection of a particle by ionisation due to, 129 Colouration of bodies by radium rays, 307 of glass, 307, 311 theory of, 309 of mica plates, 309 of bunsen flame by radium, 471 Concentration decay of radium emanation inde- pendent of, 355 of active deposit on the cathode, 398 Condensation of water on ions, 46 et seq. of emanations, 366 temperature of, for emanations, 366 Condensers use of, in measurements of currents> 108 construction of, with small capacity, 110 Conductivity of gases produced by a, /3 and y rays, 62 et seq. of radium solutions, 323 of dielectrics under radium rays, 324 Constants values of atomic and radio-active, 140 meaning of radio-active, 341 Contamination by radio-active substances, 112 Cooke natural ionisation in electroscope, 594 presence of y rays from earth, 594, 635 Cooke and Eutherford penetrating radiation from the earth,, 594, 635 Cosmical radio-activity discussion of, 653 Counting of a particles by electric method, 128 by scintillation method, 133 by cloud method, 134 by photographic method, 306 by string electrometer, 664 Crookes (Sir William) cathode rays, 76 nature of a rays, 119 scintillations due to a rays in zinc sulphide, 133 change of colour in diamond due to radiations, 299 discovery of uranium X, 330 origin of heat energy of radium, 412 Crookes and Dewar spectrum of phosphorescent light of radium, 303 INDEX 677 Crowther scattering of /3 rays from uranium, 218 scattering of ft rays by thin screens, 219 initial drop in absorption curve for |8 rays, 224 absorption of /3 rays from uranium X by elements, 227 connection of scattering with chemical constitution, 227 absorption of homogeneous j3 rays, 236 Crystallization effect of /3 rays on, 317 effect of, on activity of uranium, 453 Curie definition of, 479 Curie (P.) magnetic deflection of £ rays, 193 conductivity of liquids under radium rays, 324 decay of radium emanation, 352 effect of temperature on decay of emanation, 355 distribution of active deposit, 392 nature of the emanation, 411 Curie (Mme) discovery of activity of thorium, 10 activity of minerals, 13 activity of uranium compounds, 13 radio-activity an atomic property, 14 nature of a rays, 119 photographic record of a particles, 133 absorption of a rays from polonium, 147 action of radium on platinum, 315 decay of radium emanation, 353 effect of gravity on active deposit, 406 atomic weight of radium, 471 period of polonium, 515 decay of actinium, 521 Curie (M. and Mme) separation and purification of radium, 14 et seq. discovery of polonium, 20 concentration of polonium, 20, 21 charge carried by /3 rays, 199 changes of colour in radium salts, 302 colouration by radium rays, 307 production of ozone by a rays, 314 effect of radium rays on spark, 322 discovery of induced activity, 391 theories of radio-activity, 412 Curie (J. and P.) construction of quartz piezo-elec- trique, 104 Curie (P.) and Cheveneau magnetic properties of radium, 474 Curie (Mme) and Debierne decomposition of water by the emana- tion, 317 decomposition of water by polonium, 318 metallic radium, 473 isolation of polonium, 517 production of helium by polonium, 560 Curie (Mme) and Gleditsch (Mdlle) transformation of copper into lithium, 321 Curie (P.) and Danne absorption of emanations by solids, 378 distribution of radium emanation with temperature, 382 diffusion of radium emanation, 383 decay of active deposit of radium, 487, 492 effect of temperature on decay of active deposit of radium, 488 Curie (P.) and Dewar production of helium by radium, 556 heating effect of radium at low temperatures, 569 Curie (P.) and Laborde origin of heat energy, 412 heating effect of radium, 568 radium emanation in thermal springs. 641 Dadourian activity of thorium minerals, 546 thorium emanation from the soil, 641 Danne radio-uranium, 455 absence of uranium in pyroinorphite, 463 Danne and Curie (P.) see Curie and Danne Danysz groups of j3 rays from radium, 254 Darwin (Sir George) duration of sun's heat, 655 Darwin (C.) and Marsden complexity of thorium C, 540 Daunderer large ions in the atmosphere, 638 Davisson production of y rays by /3 rays, 282 Debierne discovery of actinium, 19, 519 decay of actinium ema'nation, 351 distribution of active deposit, 405 volume of radium emanation, 480 rate of production of helium by radium, 557 production of helium by actinium, 559 678 INDEX Debierne and Mme Curie see Curie and Debierne Decay radio-active, meaning of, 340 effect of conditions on, 342 Deflection of ions in magnetic field, 72 in electric field, 75 et seq. Delta rays 170 et seq. discovery and nature of, 170 number produced by one a particle, 173 emission of, in direction of a particle, 174 set free by |8 rays, 204 Demarcay spectrum of radium, 471 Density of radium emanation, 481 Deposit active distribution of radiations from, 312 discovery of, 391 connection of, with the emanations, 392 production and decay of, 393 of very rapid rate of decay, 395 concentration of, on the cathode, 398 distribution of, in electric field, 400 effect of pressure on distribution of, 401 range of recoil atoms from, 403 effect of gravity on distribution of, 405 velocity of carriers of, in electric field, 407 physical and chemical properties of, 408 collection of, in atmosphere, 624 theory of collection of, 627 effect of meteorological conditions on amount of, 629 distribution of, over land and sea, 630 Deposit active of actinium decay of, 394 products of quick decay in, 395 distribution of, in electric field, 399 range of recoil atoms forming, 404 analysis of, 523 rise and decay curves of, 524 radiations from, 531 Deposit active of radium discovery of, 391 distribution of, 392 decay of, 393 distribution of, in electric field, 399 distribution of, at low pressures, 401 effect of gravity on distribution of, 405 physical and chemical properties of, 408 Deposit active of radium (cont.) deduction of activity curves of, for short and long exposures, 437, 439 analysis of, 486 et seq. rise and decay curves of, by a, /3 and 7 rays, 490 et seq. total ionisation due to, 502 effect of temperature on, 502 volatility of, 505 heating effect of, 574 distribution of heating effect amongst products of, 580 presence of, in atmosphere, 625 distribution of, over land and sea, 630 Deposit active of radium of slow trans- formation analysis of, 507 et seq. variation of activity of measured, by a, j8 rays, 508 Deposit active of thorium discovery of, 391 production and decay of, 393 product of quick decay, 395 distribution of, in electric field, 398 distribution of, with pressure, 401 velocity of carriers of, 407 physical and chemical properties of, 408 deduction of rise curves of, for short and long exposures, 433 analysis of, 534 et seq. volatility of, 537 mode of transformation of, 541 presence of, in atmosphere, 626 distribution of, over land and sea, 630 Des Coudres value of elm of a particle, 122 Dewar (Sir James) rate of production of helium by radium, 557 Dewar and Crookes spectrum of luminosity of radium, 303 Dewar and Curie (P.) see Curie (P.) and Dewar Diamond scintillations in, 299 changes of colour in, 299 Dielectrics effect of radium rays on resistance of, 324 Diffusion of ions in gases, 53 et seq. general theory of, 380 methods of measuring, 383 of radium emanation, 383 of emanations through porous materials, 385 of emanations through small opening, 386 INDEX 679 Diffusion (cont.) of thorium and actinium emanations, 387 variation of, with pressure, 388 of emanation into liquids, 390 Disintegration (see Transformation) Dissociation of molecules during ionisation, 58 of gases by radiations, 316 of water by radiations, 317 Distribution of a particles according to probability, 186 of /3 rays from radium with velocity, 250 et seq. of a rays from thin films, 312 of j3 rays from uranium, 313 Doelter colouration by radium rays, 309 Dorn bursting of radium tubes, 200 deflection of ft rays in electric field, 204 discovery of radium emanation, 350 radium emanation in thermal springs, 641 Doublet theory of 7 rays, 289 Dreyer and Salomonsen effect of radium rays on quartz, 308 Duane photographic record of a particles, 133 number of delta particles emitted for each a particle, 173 total ionisation due to one curie of emanation, 502 volatilisation of radium A and B, 505 apparatus for measuring small heating effects, 585 heating effect of polonium, 586 heating effect of radium mixed with phosphorescent materials, 586 Duane and Laborde total ionisation due to one curie of emanation, 502 Durack ionisation per unit path by cathode and j8 rays, 245 Dyson radium in the sun, 654 Earth distribution of radium in, 643 heat of, 644 origin of internal heat of, 650 Ebert apparatus for measuring ionisation in atmosphere, 637 condensation of radium emanation from air, 640 Ebert and Ewers presence of radium emanation in soil, 640 Ebler attempts to separate metallic radium, 473 Effusion determination of molecular weight of radium emanation by, 386 Einstein variation of mass of electron with speed, 71 Electro-chemical methods of separation of products, 600, 603 Electrolysis of active deposits, 409 separation of products by, 600, 603 Electrometers use of, in radio-activity, 97 et seq. practical details in use of, 98 et se.q. string, 100 capacity of, and measurement of capacity of, 109 et seq. Electron velocity gained by, between collisions, 38 radius of, 72 effect of magnetic and electric field on, 72 et seq. origin of name of, 79 mass of, and variation with speed, 204 number of, in atoms, 618, 621 tables of mass and energy of, for different speeds, 667 Electroscopes description of, 90 et seq. practical points in construction of, 94 for jS and 7 rays, 94 tilted, 95 with quartz fibres, 96 Elster and Geitel experiments on radio -lead, 21 string electrometer, 101 scintillations in zinc sulphide, 133 magnetic deflection of /3 rays, 193 photo-electric action, 309 effect of radium rays on spark, 322 period of actinium B, 525 amount of radium in potassium salts, 589 presence of polonium in lead, 595 presence of active matter in atmo- sphere, 624 effect of meteorological conditions on collection of active deposit from atmosphere, 629 680 INDEX Elster and Geitel (cont.) activity of air in caves and cellars, 640 radium emanation in thermal springs, 641 Emanations from thorium, 10 from radium used as a source of radiation, 18 of short life from actinium, 19 discovery of, 348 decay of, 350 decay of radium, 351 radiations from, 356 effect of conditions on escape of, 358 effect of conditions on escape of, from radium, 361 condensation of, 364 temperature of condensation of, 366 absorption of, by liquids, 375 absorption of, by solids and charcoal, 378 diffusion of, 380 methods, of measuring diffusion of, 382 effusion of, 386 diffusion of thorium and actinium, 387 diffusion of, into liquids, 390 connection of, with active deposits, 392 number of a particles emitted by, 395 products of quick decay in, 395 correction for measurement of amount of, by 7 rays, 430 methods of measuring quantities of radium by, 659 Emanation of actinium (see actinium emanation) Emanation of radium (see radium emanation) Emanation of thorium (see thorium emanation) Energy electro-magnetic, of moving ion, 70 required to produce an ion, 158 of a particles, 164 emitted by radium, 568 et seq. discovery of, 257 absorption of, from radium, 258 connection of absorption of, with density, 263 7 rays (cont.) absorption of, by gases, 265 absorption of, from different sub- stances, 267 connection of, with primary /3 rays, 270 secondary ft rays excited by, 271 amounts of incident and emergent /3 rays excited by, 274 theory of emission of @ rays, 277 variation of ionisation in vessels pro- duced by, 278 scattering of, 279 production of, by /S rays, 282 theories of nature of, 286 discontinuous nature of, 291 ionisation anfl absorption of, 292 total ionisation produced by, from radium, 294, 579 photographic effect of, 305 decay of active deposit of radium measured by, 495 rise and fall of activity due to radium emanation measured by, 499 heating effect of, from radium, 578 connection of, with /3 rays, 610 theory of origin of, 611 number and energy of, 614 emission of, from earth, 634 decrease of intensity of, in atmosphere with height, 636 use of, in comparing quantities of radium, 657 Gates (Miss) effect of temperature on active deposit, 409 Geiger decrease of velocity of a particles with range, 142 ionisation due to one a particle, 153 decrease of number of a particles with distance, 157 scattering of a rays, 180 laws of scattering of a rays by thin films, 185 probability variation of a particles, 187 complexity of emanations, 357 a particles from actinium emanation, 396 properties of thorium A, 535 Geiger and Kovarik ionisation by /3 rays per unit path, 246 ionisation produced by /3 particles, from a number of active substances, 250 Geiger and Marsden large angle scattering of a rays, 183 682 INDEX Geiger and Marsden (cont.) double scintillations, 191 number of a particles from the ema- nations, 395 Geiger and Nuttall range of a particles, 162 complex nature of a rays from uranium, 448 range of a particles from thorium emanation and thorium A, 535 relation between range and period of transformation, 607 Geiger and Rutherford charge carried by a particle, 52, 136 electrical method of counting a particles, 129 atomic and radio-active constants, 140 number of a particles from uranium minerals, 447 radio-active nomenclature, 524 properties of thorium A, 535 number of a particles from thorium, 551 number of a particles emitted by uranium and thorium, 560 Geiger, Rutherford and Bateman probability variations of a particles, 188 Geitel natural ionisation of air, 592, 624 Geitel and Elster see Elster and Geitel Gerdien apparatus for measuring ionisation in atmosphere, 638 Giebeler radium in a new star, 653 Giesel separation of radium by crystallisa- tion, 15 preparation of commercial salts of radium, 17 discovery of emanium, 19 experiments on radio-lead, 21 phosphorescence of zinc sulphide by a rays, 133, 297 magnetic deflection of /9 rays, 193 spectrum of luminosity of actinium, 304 colouration by radium rays, 308 dissociation of water by radium, 317 effect of radium rays on the eye, 328 flame spectrum of radium, 471 separation of radium E, 515 discovery of emanium, 519 separation of actinium X, 528 heating effect of radium, 569 Giesel and Starke luminosity of air due to rays from polonium, 304 Gimingham and Rossignol decay of thorium emanation, 351 Glasson ionisation by cathode rays per unit path, 245 Gleditsch (Mdlle) connection between lithium and copper in radio-active minerals, 321 ratio of radium to uranium in minerals, 463 Glew scintillations in the diamond, 299 Gockel activity of atmosphere at high alti- tudes, 631 large ions in the atmosphere, 638 Godlewski absorption of /3 rays, 225 absorption of 7 rays from actinium, 267 solubility of uranium X in water, 453 separation of actinium X, 528 Goldstein canal rays, 81 condensation of actinium emanation, 371 Gonders, Hofmann, and Wolfl constituents of radio-lead, 510 Gradient potential in ionised air, 65 Grant and Steele micro-balance, 481 Gray (J. A.) deflection of j3 rays from radium E, 212 production of 7 rays by /3 rays, 213 production of 7 rays by /3 rays from radium E, 283 distribution of 7 rays excited by /3 rays, 285 emission of characteristic radiations by 7 rays, 286 escape of helium from minerals by grinding, 563 Gray (J. A.) and Wilson (W.) complex nature of /3 rays from radium E, 238 Gray (R. W.) and Ramsay atomic weight of radium, 472 volume of radium emanation, 480 density of radium emanation, 481 vapour pressure, 484 Gravity effect of, on distribution of active deposit, 405 INDEX 683 Greinacher charge carried by a rays, 157 distribution of ft rays from uranium, 313 conductivity of dielectrics with polonium rays, 326 Greinacher and Marckwald period of polonium, 515 Griiner theory of successive changes, 418 Hackett variation of emergence /3 radiation with atomic weight, 275 Hahn discovery of meso-thorium and radio- thorium, 11, 544, 547 range of a particles, 162 on radio-active recoil, 175 separation of new products by recoil, 176 recoil of radium C from radium B, 177 decay of thorium emanation, 351 growth of radium in thorium, 467 radio-actinium, 520 recoil of actinium X from actinium, 527 separation and properties of radio- actinium, 529 analysis of a rays from thorium C, 539 Hahn and Meitner exponential law of absorption, 211 coefficient of absorption of /3 rays, 225 /3 radiations from radium, 474 complex nature of radium C, 500 /3 rays from radium D, 514 separation of actinium C by volatili- sation, 526 separation of actinium D, 527 radiations from actinium D, 532 analysis of thorium C, 539 complexity of thorium C, 540 separation of thorium D, 542 j3 radiation from thorium D, 542 /3 rays from meso-thorium 2, 548 Hahn, v. Baeyer and Meitner see v. Baeyer, Hahn and Meitner Hahn and Eutherford velocity and mass of a particles from radio-thorium, 128 Hahu and Sackur identity of emanations from actinium and emanium, 351, 520 period of actinium B, 525 Haitinger and Ulrich separation of radium, 16 Halos origin and dimensions of, 309 Hardy and Anderson luminosity of eye due to radium rays, 328 Hardy and Wilcock (Miss) action of radium rays on iodoform, 315 Hartmann spectrum of luminosity of actinium, 304 Hauser on velocity of expulsion of delta rays, 171 Heat emission of, by radium, 568 emission of, by radium at low tem- peratures, 570 measurements of emission of, from radium, 571 connection of emission of, with the radiations, 571 emission of, by the radium emanation and its products, 573 calculated emission of, by radium and its emanation, 576 emission of, due to /3 and 7 rays, 578 distribution of emission of, between radium and its products, 580 total emission of, by the emanation, 581 emission of, by uranium and thorium, 583 methods of measurement of emission of, 585 emission of, by radio-active matter in earth, 650 origin of earth's internal, 650 origin of sun's, 655 Heating effect suggested explanation of, for radium, 412 importance of, in radio-active theories, 415 Heaviside electrical mass of charged body, 71 Helium connection of, with a particles, 137 calculated rate of production of, by radium, 141 discovery of, 553 production of, by radium and its emanation, 555 origin and rate of production of, by radium, 556 production of, by radio-active sub- stances, 559 connection of, with age of minerals, 562 amount of, in radio-active minerals, 563 amount of, in ordinary substances, 564 684 INDEX Helium (cont.) age of geological strata by estimation of, 566 Helmholtz and Kicharz action of ions on steam jet, 47 Hemptinne effect of radium emanations on elec- trodeless discharge, 323 Henning conductivity of barium radium- solu- tion, 323 radium collector, 324 recombination of ions with active deposit, 400 Henning and Kohlrausch conductivity of radium bromide solutions, 323 Henriot condensation of actinium emanation, 371 activity of potassium, 588 Herrmann and Marckwald luminosity of air due to a rays, 303 Herschfinkel attempts to separate metallic radium, 473 , concentration of radium D, 511 Hess absorption of y rays from radium by air, 267 Hess and St Meyer heating effect of radium, 571 Hess and v. velocity of, in electric field, 28, 31 production of, by collision, 36 et seq. recombination of, 38 mobility of, 41 et seq. difference between positive and nega- tive, 42, 44 effect of water vapour on mobility of, 44 variation of mobility of, with temper- ature and pressure, 46 condensation of water on, 46 et seq. difference between positive and nega- tive, 49 charge carried by, 50 et seq. diffusion of, 53 et seq. size and nature of, 56 et seq. number and distribution of, from active substances, 58 magnetic field produced by motion of, 69 electrical mass of, 70 et seq. total number produced by a particle, 153 distribution of, along path of a particle, 154 effect of velocity of a particle on pro- duction of, 157 energy required to produce, by a particle, 158 total number of, produced by ft rays from radium, 230, 579 number of, produced per cm. by ft particle, 245 total number of, produced by one /3 ray, 250 total number of, produced by absorp- tion of -7 rays from radium, 294 INDEX 685 Ions (cont.) number produced by penetrating rays from earth, 637, 640 types of, in the atmosphere, 638 excess of positive over negative, in atmosphere, 639 photographic record of trails of, pro- duced by a and ft rays, 663 lonisation theory of, for gases, 26 et seq. variation of, with pressure and nature of gas, 31 difficulty of saturation of, with a rays, 32 et seq. by collision, theory of, 36 et seq. mechanism of, 56 et seq. distribution of, due to active bodies, 58 total, due to a rays in different gases, 65 standards of, 111 relative, produced by a, 8 and 7 rays, variation of, from active matter with distance, 146, 159 of the a particle along its path, 149, 154 total, due to one a particle, 153 of a particles in air and hydrogen, 154 total produced by one gram of radium, 155 explanation of variation due to pencil of a rays, 156 variation of, with velocity, 157 energy required for, 158 production of, by recoil atoms, 179 total, produced by j3 rays from one gram of radium, 230, 579 variation of, with velocity of 8 particle, 245 law of decrease of, with velocity, 249 produced per cm. by 8 rays from active substances, 250 variation of, for y rays with material of electroscope, 278 origin of, produced by 7 rays, 293 total produced by absorption of 7 rays, 294, 579 natural, in sealed vessels, 591 variation of, in sealed vessels with gas and pressure, 592 causes of, in sealed vessels, 593 natural, in screened vessels, 594 measurement of, in atmosphere, 637 character of, in atmosphere, 638 radio-active origin of, in atmosphere, 639 lonisation current nature of, 26 variation of, with voltage, 27 lonisation current (cont.) difficulty of saturation of, with a rays, 32 increase of, by collision, 36 variation of, with voltage for surface distribution, 67 et seq. measurement of, 93 measurement of, by steady deflection method, 101 by balance and compensation methods, 103 apparatus for measurement of, 106 direct measurement of, 108 Ionium discovery of, 21 use of, as potential collector, 324 connection of, with uranium, 444 activity of, in uranium minerals, 446 method of discovery of, 455 growth of radium from, 456 radiation from and chemical proper- ties of, 457 discussion of period of, 458. decay of, in zinc sulphide and wille- mite, 301 of radium compounds, 302 spectrum of, in radium salts, 302 spectrum of, in actinium salts, 304 of air surrounding polonium, 304 Lutz string electrometer, 101 Macallum and McLennan variation of penetrating radiation with altitude, 636 Mache absorption of radium emanation by liquids, 375 radium emanation in thermal springs, 641 Mache and Meyer (St.) total ionisation due to one curie of emanation, 502 Mache and v. Schweidler velocity of ions in atmosphere, 638 Mackenzie value of e/m for a particle, 122 complex nature of a rays from radium, 143 on emergence and incidence ft radia- tion, 274 Madsen scattering of ft rays by thin screens, 219 scattered 7 radiation, 279 Madsen and Bragg variation of emergence ft radiation with atomic weight, 275 Magnetic field produced by an ion in motion, 69 688 INDEX Makower charge carried by /3 rays of radium, 202 absorption of /3 rays, 203 diffusion of radium emanations, 385 distribution of active deposit at low pressures, 401 effect of temperature on decay of products of radium, 503 volatilisation of radium A, B and C, 505 Makower and Evans see Evans and Makower Makower and Fajans see Fajans and Makower Makower and Moseley emission of 7 rays by radium B, 269, 488 effect of 7 rays from radium B on rise curve, 495 Makower and Buss radio-active recoil, 375 absorption of recoil atoms, 176 recoil of radium C from radium B, 177 range of recoil atoms, 405 effect of temperature on decay of products of radium, 503 Marckwald separation of radio-tellurium, 20 identity of emanations from actinium and emanium, 520 separation of radium and meso- thorium, 548 Marckwald and Greinacher period of polonium, 515 Marckwald and Herrmann luminosity of air due to a rays, 303 Marckwald and Russell ratio of radium to uranium in minerals, 463 Marsden effect of bombardment on scintilla- tions, 300 decay of luminosity produced by, 300, 301 Marsden and Barratt see Barratt and Marsden Marsden and Darwin complexity of thorium C, 540 Marsden and Geiger see Geiger and Marsden Marx velocity of X rays, 289 Masek and Kucera see Kucera and Masek Mass electrical, of moving ion, 70 et seq. of electron at slow speeds, 79 of canal rays, 81 measurement of, for a particle, 121 et seq. Mass (cont.) of atom of H, 140 of electron and variation with speed, 2Q4, 667 origin of, 618 distribution of, in structure of atom,. 619 Matter apparent radio-activity of ordinary^ 590 McClelland distribution of scattered /3 rays, 214 connection of scattering with chemical constitution, 215 theory of absorption of ft rays, 231 absorption of 7 rays, 259 McClung coefficient of recombination of ions, 40 ionisation curve for radium C, 149 McClung and Rutherford energy emitted from active sub- stances, 411, 568 McCoy uranium standards, 111 relation between copper and lithium in radio-active minerals, 321 activity of uranium minerals, 445 constancy of radium to uranium in minerals, 460 surface distribution of radium in pyromorphite, 463 McCoy and Ross activity of thorium minerals, 546 Mclntosh and Eve amount of radium in rocks, 646 McLennan emission of delta rays, 173 penetrating radiation from earth, 594, 634 activity of old specimens of lead, 595 activity of snow, 627 effect of spray on collection of active matter, 627 McLennan and Burton activity of ordinary matter, 593 McLennan and Kennedy see Kennedy and McLennan McLennan and Macallum see Macallum and McLennan Meitner separation of components of thorium C, 541 Meitner and Hahn see Hahn and Meitner Meitner, v. Baeyer and Hahn see v. Baeyer, Hahn and Meitner Meso-thorium discovery of, 11 effect of, on decay of thorium X, 338 separation and property of, 546 INDEX 689 Meso-thorium (cont.) variation in amount of, in prepara- tions of thorium, 546 period of, 547 separation with thorium X, 547 chemical properties of, 548 variation of activity with time, 549 separation of, on commercial scale, 550 Meso-thorium 2 absorption of 7 rays from, 268 proportion of 7 rays to ft rays, 271 separation and properties of, 548 radiations from, 548 Methods of measurement in radio-activity, 87 et seq. comparison of photographic and electrical, 87 description of electrical, 88 et seq. 