INDEX.

Strutt conductivity of gases for radiation, 63, 64 conductivity of gases produced by γ rays, 64, 183 negative charge carried by β rays, 122 et seq. absorption of β rays proportional to density, 136 nature of α rays, 142 attempt to measure charge of α 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-activity 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 actinium, 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 activity in atmosphere, 518 effect of, on natural ionization of air, 536
Theories of radio-activity, review of, 437 et seq. discussion of, 441 et seq. disintegration theory, 445 et seq.
Thermo-luminescence, 207
Thomson, J. J. relation between current and voltage for ionized gases, 34 difference between ions as condensation 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 α rays, 154 theory of radio-activity, 440 cause of heat emission 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 thorium, 29 nature of radiations from, 109 β rays from, 114 α rays from, 141 γ 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, 351 et seq. rayless change in, 352 explanation of initial portion of decay curve, 358 explanation of initial portion of recovery curve, 358 effect of successive 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-activity, 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, 448 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 seq.
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

559