INDEX.

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. secondary rays produced by γ rays, 189 measurement of radio-activity by means of, 442, 467 conservation of radio-activity measured by, 471

545