Page:Radio-activity.djvu/599

Spinthariscope
  description of, 158

Springs
  emanation from water of, 513

Stark
  energy to produce an ion, 58

Stoney, Johnstone
  use of term electron, 76

Strauss and Hofmann
  radio-active lead, 27

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