INDEX 
Current (cont.) 
variation of with pressure of gas, 
58 et seq. 
variation of, with nature of gas, 61 
measurement of, by galvanometer, 69 
measurement of, by electroscope, 70 
et seq. 
measurement of, by electrometer, 84 
measurement of, by quartz piezo- 
électrique, 87 
magnitude of, for one gram of radium, 
156 
Danne and Curie, P. 
diffusion of radium emanation, 231 
decay of excited activity from radium, 
262 
occlusion of 
solids, 264 
Danysz 
action of radium rays on skin, 177 
Darwin, G. H. 
age of sun, 343 
Debierne 
actinium, 22 
emanation from actinium, 208 
effect of magnetic field on activity 
excited from actinium, 288 
barium made active by actinium, 289 
Debierne and Curie 
evolution of gas from radium, 175 
active gas evolved from radium, 210 
phosphorescence produced by radium 
emanation, 211 
distribution of luminosity, 211 
rate of production of emanation inde- 
pendent of pressure, 224 
effect of pressure on excited activity, 
282 
Decay 
of heating effect of emanation, 162 
of activity of Th X, 180 
of activity of Ur X, 182 
significance of law of, 189 
effect of conditions on the rate of, 190 
of activity of thorium emanation, 200 
of activity of radium emanation, 206 
excited activity due to thorium for 
long exposure, 256 
excited activity due to thorium for 
short exposure, 258 
excited activity due to radium, 261 
excited activity of slow decay due to 
radium, 264, 291 
excited activity from atmosphere, 351 
et seq. 
of activity of rain and snow, 356 
of emanation from earth, 358 
differences in, of excited activity from 
atmosphere, 368 
radium emanation in 
387 
Deflection 
of rays in a magnetic field, 92 
of 8 rays in a magnetic field, 95 et seq. 
of 6 rays in an electrostatic field, 106 
of a rays in a magnetic field, 117 et seq. 
of a rays in an electrostatic field, 121 
of ‘‘ions activants” in a magnetic 
field, 288 
Demarcay 
spectrum of radium, 16 
Des Coudres 
magnetic and electric deviation of a 
rays of radium, 122 
determination of e/m for a rays, 122 
velocity of cathode rays diminished in 
passage through matter, 139 
Dewar 
emission of heat from radium in liquid 
hydrogen, 160 
Dewar and Crookes 
absence of nitrogen spectrum in phos- 
phorescent light of radium at low 
pressures, 169 
Dielectrics 
conduction of, under radium rays, 172 
Diffusion 
of ions, 49 
of radium emanation into gases, 228 
et seq. 
of thorium emanation into gases, 233 
of radium emanation into liquids, 235 
Discharge 
action of rays on spark and electrode- 
less, 171 
Disintegration 
account of theory of, 126, 193, 323 et 
seq. 
list of products of, 326 
helium a product of, 327 et seq. 
rate of, in radio-elements, 332 et seq. 
emission of energy in consequence of, 
336 et seq. 
possible causes of, 338 et seq. 
of matter in general, 347 et seq. 
Dissipation of charge 
in closed vessels, 351, 373 
in cayes and cellars, 357 
effect of pressure and nature of gas 
on, 376 et seq. 
effect of material of vessel on, 378 et seq. 
Dolezalek 
electrometer, construction of, 78 e¢ seq. 
Dorn 
charge carried by radium rays, 104 
electrostatic deflection of 6 rays from 
radium, 106 
discovery of radium emanation, 205 
effect of moisture on emanating power 
of thorium, 214 
electrolysis of radium solution, 276 
25—2 
