Page:Radio-activity.djvu/589

  from metals, 538

Emanating power
  measurement of, 254
  effect of conditions on, 255
  regeneration of, 256

Emanium or "emanating substance" of Giesel (see Actinium) discovery of, 21 separation and properties of, 21 similarity of, to actinium, 21 emanation from, 249 excited activity produced by, 311 action of an electric field on, 323 Energy of α particle, 156 of β particle, 196 comparison of, for α and β particles, 196 emitted from radium in form of heat, 419 et seq. emission of, from the emanation, 431 emission of, from radio-active products of radium, 433 total emission of, from 1 gram of radio-elements, 474 et seq. latent store of, in matter, 475 Eve conductivity of gases exposed to X rays, 64 conductivity of gases exposed to X rays and γ rays, 183, 184 secondary rays produced by β and γ rays, 189 et seq. magnetic deflection of secondary rays from γ rays, 193 variation of activity of radium with concentration, 467 amount of radium emanation in the atmosphere, 524 et seq. ionization due to emanation in atmosphere, 526 et seq.

Evolution of matter
  evidence of, 497

Ewers and Ebert
  emanation from the earth, 508

Excited radio-activity
  discovery and properties of, 295 et seq. concentration of, on negative electrode, 297 connection of, with the emanations, 298 removal of, by acids, 300 decay of, due to thorium, 302 decay of, for short exposure to thorium, 304 effect of dust on distribution of, 305 decay curves for different times of exposure, 306 et seq. decay of, from radium, 306 decay curves of, measured by α rays, 308 decay curves of, measured by β rays, 309 decay curves of, from actinium, 311 of radium, of very slow decay, 311 effect of solution on, 312 electrolysis of active solutions, 313 effect of temperature on, 315 variation with electric field, of amount of, 316 effect of pressure on distribution of, 317 transmission of, 318 from actinium and emanium, 323 heat emission due to, 425 et seq. from the atmosphere, 501 et seq. decay of, 502 due to emanation in atmosphere, 504 distribution of, on surface of the earth, 504 concentration of, on prominences of the earth, 504 of rain and snow, 506 produced by emanation from tap water, 510 effect of meteorological conditions on amount of, 517 et seq. amount of, at Niagara Falls, 520 rate of decay of, dependent on conditions, 522 et seq.

Exner and Haschek
  spectrum of radium, 17

Eye
  action of radium rays on, 217


Fehrle
  distribution of excited activity on a plate in electric field, 318

Fluorescence
  produced in substances by radium rays, 18
  produced in substances by radium and polonium rays, 201 et seq.

Fog
  large amount of excited activity during, 518

Forch
  loss of weight of radium, 474


γ rays
  relative conductivity of gas exposed to γ and hard X rays, 64, 184
  discovery of, 179
  absorption of, by matter, 179 et seq.
  connection between absorption of, and density, 182
  discussion of nature of rays, 182 et seq.