396 
Runge and Bédlander 
evolution of gas from radium, 176 
Russell 
photographic action of substances, 68 
Saturation current 
meaning of, 30 et seq. 
application of, to measurements of 
radio-activity, 69 
measurement of, 82 et seq. 
Schmidt 
discovery of radio-activity of thorium, 
10 
Schmidt and Wiedemann 
thermo-luminescence, 170 
Schuster 
radio-activity of matter, 371 
Schweidler and Meyer 
magnetic deviation of 8 rays by electric 
method, 95 
absorption of 8 rays of radium, 113 
Scintillations 
discovery of in zine sulphide screen, 
127 
connection of, with a rays, 127 
illustration of by spinthariscope, 127 
cause of, 128 
production of, by action of electric 
field, 128 > 
Searle 
apparent mass of moving charged 
body, 109 
Secondary rays 
examination of, 
method, 146 
examination of, by electrical method, 
148 
Selenium 
action of radium rays on, 171 
Simon 
value of e/m for cathode rays, 111 
Smolan, Beattie and Kelvin 
discharging power of uranium rays, 7 
Snow 
radio-activity of, 356 
decay of activity of, 356 
Soddy 
comparison of photographic and elec- 
trical action of uranium rays, 68 
nature of rays from Ur X, 294 
Soddy and Ramsay 
evolution of gas from radium, 176 
chemical nature of the emanation, 
227 
gaseous nature of the emanation, 227 
volume of the emanation, and change 
with time, 313 
helium from radium emanation, 320 
Soddy and Rutherford 
separation of ThX, 179 
by photographic 
INDEX 
Soddy and Rutherford (cont.) 
decay of activity of Th X, 181 
recovery of activity of thorium, freed 
from Th X, 181 
decay of activity of UrX, 182 
recovery of activity of uranium, freed 
from Ur X, 182 
explanation of decay and recovery 
curves, 183 
rate of production of Th X, 186 
theory of decay of activity, 188 
influence of conditions on rate of 
decay and recovery of activity, 190 
et seq. 
disintegration hypothesis, 194, 324 
decay of activity of radium emanation, 
206 
measurements of emanating power, 
213 
effect of temperature, moisture, and 
solution, on emanating power, 214 
regeneration of emanating power, 215 
constant rate of production of emana- 
tion of radium and thorium, 216 
et seq. 
source of thorium emanation, 220 
radiations from the emanation, 222 
chemical nature of emanation, 226 
condensation of emanations of radium 
and thorium, 236 et seq. 
temperature of condensation of emana- 
tion, 238 et seq. 
effect of successive precipitations on 
activity of thorium, 2J6 
recovery of activity of radium, 300 
conservation of radio-activity, 309 
theory of radio-activity, 318 
theory of radio-active change, 324 
Soil 
radio-activity of, 362 
difference in activity of, 362 
Solution 
coloration of, by radium, 15 
of emanation X in acids, 275 
electrolysis of active, 276 
Source 
of the thorium emanation, 220 
of radium emanation, 222 
Spark 
action of radium rays on, 171 
Spectrum 
spark spectrum of radium, 15, 16 
flame spectrum of radium, 17 
effect of a magnetic field on spectrum 
of radium, 17 
of polonium, 20 
of phosphorescent light of radium 
bromide, 169 
of helium in radium gases and emana- 
tion, 329 

