INDEX 
Spectrum (cont.) 
of emanation, 329 
Spinthariscope 
description of, 127 
Springs 
emanation from water of, 360 
Stark 
energy to produce an ion, 55 
Strauss and Hofmann 
radio-active lead, 25 
Strutt 
conductivity of gases for radiation, 
61, 62 
negative charge carried by radium 
rays, 104 
absorption of 8 rays proportional to 
density, 113 
nature of a rays, 116 
conductivity of gases produced by 
y rays, 62, 144 
absorption of radium rays from sun 
by atmosphere, 343 
radio-activity of ordinary matter, 378 
emanation from mercury, 381 
Sun 
effect of radium in, 342 
age of, 343 
Temperature 
of radium above surrounding space, 
158 
effect of, on intensity of radiations 
from uranium and radium, 173 
effect of, on luminosity, 173 
rate of decay of radium emanation 
unaffected by, 208 
of condensation of emanations, 238 
et seq. 
rate of decay of thorium emanation 
unaffected by, 246 
effect of, on excited activity, 277 
effect of, on amount of excited activity 
in atmosphere, 364 et seq. 
effect of, on natural ionization ofair,377 
Theories 
of radio-activity, review of, 316 
discussion of, 320 
disintegration theory, 324 
Thermo-luminescence, 170 
Thomson, J. J. 
relation between current and voltage 
for ionized gases, 31 
difference between ions as condensa- 
tion nuclei, 46 
charge on ion, 47 
theory of electrometers, 85 
path of charged particle in uniform 
magnetic field, 96 
apparent mass of moving charged 
body, 108 
397 
Thomson, J. J. (cont.) 
structure of atom, 126, 347 
theory of radio-activity, 319 
cause of heat emission from radium, 
321 
possible causes of disintegration of 
radium, 342 
nature of electrons, 347 
emanation from tap-water and deep 
wells, 360 
Thomson, J. J., and Rutherford 
ionization theory of gases, 28 et seq. 
Thorium 
discovery of radio-activity of, 10 
emanation from, 11 
preparation of non-radio-active tho- 
rlum, 25 
nature of radiations from, 90 et seq. 
B rays from, 95 et seq. 
a rays from, 115 et seq. 
y rays from, 141 et seq. 
rate of emission of energy by, 154 
separation of Th X from, 179 
recovery of activity of, 181 
disintegration of thorium, 193 
emanation from, 197 
properties of emanation from, 198 e¢ 
seq. 
diffusion of emanation from, 233 
condensation of emanation from, 236 
et seq. 
excited radio-activity from, 250 et seq. 
successive changes in emanation X of, 
272 
explanation of initial portion of decay 
curve, 295 et seq. 
explanation of initial portion of re- 
covery curve, 295 et seq. 
effect of successive precipitations on, 
296 
recovery curve after large number of 
precipitations, 297 
theory of decay curve of Th X, 298 
non-separable activity of, 296, 304 
radiations from active products of, 
304 et seq. 
division of activity amongst active 
products of, 306 et seq. 
conservation of radio-activity of, 308 
et seq. 
résumé of results, 311 et seq. 
theories of radio-activity of, 316 et seq. 
discussion of theories of radio-activity, 
320 et seq. 
source of energy of radiations, 320 e¢ 
seq. 
theory of radio-active change, 322 et 
seq. 
table of radio-active products of, 326 
rate of change of, 332 et seq. 
