INDEX.

Schenck radium emanation in springs, 513
Schenck and Richarz theory of radio-activity, 441
Schmidt discovery of radio-activity of thorium, 10
Schmidt and Wiedemann thermo-luminescence, 207
Schuster number of ions per c.c. in air of Manchester, 528 radio-activity of matter, 529
Schweidler and Mache velocity of ions in air, 528
Schweidler and Meyer magnetic deviation of β rays by electrical method, 113 absorption of β rays of radium by matter, 136 activity proportional to amount of uranium, 195 emanation from uranium, 348 effect of crystallization on activity of uranium, 349 rate of decay of radio-tellurium, 411
Scintillations discovery of, in zinc sulphide screen, 158 connection of, with α rays, 158 illustration of, by spinthariscope, 158 cause of, 160 production of, by action of electric field, 160
Searle apparent mass of moving charged body, 71, 127
Secondary rays examination of, by photographic method, 187 examination of, by electrical method, 188 production of, by β and γ rays, 189 et seq. from different materials, 191 amount of, depends upon atomic weight, 192 magnetic deflection of, 193
Seitz absorption of electrons by matter, 137 et seq.
Selenium action of radium rays on, 208
Simon value of e/m for cathode rays, 75, 129
Simpson amount of excited activity in north of Norway, 519
Slater, Miss effect of temperature on active deposit of thorium, 354
Smolan, Beattie and Kelvin discharging power of uranium rays, 7
Snow radio-activity of, 506 decay of activity of, 507
Soddy comparison of photographic and electrical action of uranium rays, 83 nature of rays from Ur X, 347 production of radium from uranium, 463
Soddy and Ramsay evolution of gas from radium, 215 production of hydrogen and oxygen from radium, 215 chemical nature of the emanation, 268 gaseous nature of the emanation, 268 volume of the emanation, and change with time, 289 helium from radium emanation, 291 amount of helium produced by radium, 480
Soddy and Rutherford separation of Th X, 220 decay of activity of Th X, 221 recovery of activity of thorium freed from Th X, 221 decay of activity of Ur X, 223 recovery of activity of uranium freed from Ur X, 223 explanation of decay and recovery curves, 224 rate of production of Th X, 227 theory of decay of activity, 229 influence of conditions on rate of decay and recovery of activity, 233 disintegration hypothesis, 234 decay of activity of radium emanation, 247 measurements of emanating power, 254 effect of temperature, moisture, and solution, on emanating power, 255 regeneration of emanating power, 256 constant rate of production of emanation of radium and thorium, 257 source of thorium emanation, 261 radiations from the emanation, 264 chemical nature of emanation, 267 condensation of emanations of radium and thorium, 277 temperature of condensation of emanation, 278 effect of successive precipitations on activity of thorium, 358 recovery of activity of radium, 372 theory of radio-activity, 439 theory of radio-active change, 445 conservation of radio-activity, 469

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