386 
Condensation 
of water round the ions, 43 et seq. 
of emanations, 236 et seq. 
experimental illustration of, 237 
temperature of, 238 
difference between point of, for eman- 
ations of thorium and radium, 243 
from air sucked up from the earth, 
B57 
Conductivity 
of gases exposed to radiations, 28 
et seq. 
variation of, with pressure, 58 et seq. 
variation of, with nature of gas, 61 
comparison of, for gases exposed to 
a, 8 and vy rays, 61 et seq. 
of insulators, 172 
of air in closed vessels, 351, 373 
increase of, with time, in a closed 
vessel, 351 
of air in caves and cellars, 357 
variation of in closed vessels with 
pressure and nature of gas, 376 
variation of with temperature for air 
in closed vessels, 377 
Conservation of radio-activity 
examples of, 308 
Cooke, H. L. 
penetrating rays from the earth, 366 
number of ions per c.c. in closed 
vessels, 376 
radio-activity from ordinary matter, 
378 
Corpuscle 
(see Electron) 
Crookes (Sir W.) 
spectrum of polonium, 20 
separation of Ur X, 178 
nature of a rays, 116 
scintillations produced by radium, 127 
spinthariscope, 127 
number of scintillations independent 
of pressure and temperature, 128 
theory of radio-activity, 319 
cathode rays, 347 
Crookes and Dewar 
absence of nitrogen spectrum in phos- 
phorescent light of radium at low 
pressures, 169 
Curie, Mme 
permanence of uranium rays, 6 
discovery of radio-activity of thorium, 
10 
radio-activity of uranium and thorium 
minerals, 11 
relative activity of compounds of ura- 
nium, 12 
coloration of radium crystals, 15 
spectrum of radium, 15 
nature of a rays, 116 
INDEX 
Curie, Mme (cont.) 
absorption of a rays from polonium, 
31 
secondary radiation tested by electric 
method, 148 
slowly decaying excited activity from 
radium, 264 
bismuth made active by solution of 
barium, 289 
recovery of activity of radium, 303 
Curie, P. 
magnetic deviation of radium rays by 
electric method, 96 
heat emission of radium at low tem- 
perature and variation of heat emis- 
sion with age of radium, 159, 160 
conductivity of dielectrics under 
radium rays, 172 
radio-activity of radium unaffected by 
temperature, 173 
decay of activity of radium emana- 
tion, 206 et seq. 
discovery of excited radio-activity 
from radium, 250 
nature of the emanation, 318 
Curie, M. et Mme 
discovery of radium, 13 
charge carried by radium rays, 102 
luminosity of radium compounds, 168 
production of ozone by radium rays, 
174 
coloration of glass by radium rays, 174 
theory of radio-activity, 318 
possible absorption by radio-elements 
of unknown radiations, 321 
Curie, J. et P. 
quartz piezo-électrique, 87 et seq. 
Curie, P. et Danne 
diffusion of radio-active emanation, 
231 
decay of excited activity from radium, 
262 
occlusion of radium emanation in 
solids, 264 
Curie, P. and Debierne 
active gases 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 amount of ex- 
cited activity, 282 
Curie, P. and Laborde 
heat emission of radium, 158 
origin of heat from radium, 319 
Current 
through gases, 28 et seq. 
variation of with distance between 
the plates, 56 et seq. 

