adjustment and screening of, 95
special key for, 97
application of, to measurements of radio-activity, 97 et seq.
measurement of current by, 100
capacity of, 101
use with steady deflection, 103
use with quartz piezo-électrique, 105
Electron
definition of, 56
production of, under different conditions, 76 et seq.
identity of β rays with electrons, 120 et seq.
variation of apparent mass of electron with velocity, 127 et seq.
evidence that mass of electron is electro-magnetic, 129 et seq.
diameter of, 131
Electroscope
description of, used by Curie, 85
construction of, for accurate measurements, 86
use of, in measurements of minute currents, 86
of C. T. R. Wilson, 89
use of, in measuring conductivity of air in closed vessels, 531 et seq.
use of, for determining radio-activity of ordinary matter, 537
Elster and Geitel
radio-active lead, 27
effect of magnetic field on conductivity produced in air by β rays, 113
scintillations produced by active substances, 158
action of radium rays on spark, 208
photo-electric action of body, coloured by radium rays, 214
radio-active matter in earth, 494
discovery of excited activity in atmosphere, 501
emanations from the earth, 507
radio-activity of air in caves, 507
radio-activity of the soil, 515
radio-activity of fango, 516
variation of radio-activity in atmosphere with meteorological conditions, 517
effect of temperature and pressure on atmospheric radio-activity, 518
Emanation
of thorium, discovery and properties of, 238
methods of measurement of, 240
decay of activity of, 241
effect of thickness of layer on amount of, 243
increase of, with time to a maximum, 245
of radium, 246
decay of activity of, 247
of actinium, properties of, 249
of radium, phosphorescence produced by, 251
rate of emission of, 254
effect of conditions on rate of emission of, 255
regeneration of emanating power, 256
continuous rate of production of, 257
source of thorium emanation, 261
source of radium and actinium emanation, 263
radiations from, 263
effect of pressure on production of, 265
chemical nature of, 267
experiments to illustrate gaseous nature of, 268
rate of diffusion of radium emanation, 269
rate of diffusion of thorium emanation, 275
diffusion of, into liquids, 276
condensation of, 277
temperature of condensation of, 280
volume of, from one gram of radium and thorium, 288
measurement of volume of, from radium, 289
diminution of volume of, 290
spectrum of emanation, 292
connection between emanation and excited activity, 298
effect of removal of, on activity of radium, 371 et seq.
fraction of activity of radium due to, 374
effect of rate of escape of, on activity of radium, 374
heat emission of, 420, 431
variation of heat emission with time, 421 et seq.
enormous emission of energy from emanation, 431
radio-activity of atmosphere due to emanations, 504
sucked up from the earth, 507
in caves, 507 et seq.
rate of decay of activity of, from the earth, 508
condensation of, from the atmosphere, 510
in well water and springs, 510 et seq.
from "fango," 516
effect of meteorological conditions on amount of, in atmosphere, 517 et seq.
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