390 
Excited radio-activity (cont.) 
possible connection of polonium and 
radio-tellurium with, 290 et seq. 
from the atmosphere, 351 et seq. 
concentration of, on negative elec- 
trode, 351 
decay of, 353 
due to emanation 
354 
distribution of, on surface of earth, 
354 
concentration of, on prominences of 
the earth, 354 
of rain and snow, 356 
decay of, on rain and snow, 356 
due to emanation from earth, 357 
produced by emanation from tap 
water, 360 
effect of meteorological conditions on 
amount of, 364 
amount of, at Niagara Falls, 366 
rate of decay of, dependent on con- 
ditions, 368 
Exner and Haschek 
spectrum of radium, 17 
Eye 
action of radium rays on, 177 
in atmosphere, 
Fehrle 
distribution of excited activity on a 
plate, in electric field, 282 
Fluorescence 
produced in substances by radium 
rays, 18 
produced in substances by radium 
and polonium rays, 166 
Fog 
large amount of excited activity, 
during, 365 
Forch 
loss of weight of radium, 336 
7 rays 
discovery of, 141 
absorption of, by matter, 142 
connection between absorption of, and 
density, 143 
discussion of nature of rays, 143 et seq. 
conservation of radio-activity mea- 
sured by, 311 
measurement of radio-activity by 
means of, 321, 339 
Gases 
evolved by radium, 175 
presence of helium in gases from 
radium, 176, 327 et seq. 
Gates, Miss F. 
effect of temperature on excited ac- 
tivity, 278 
discharge of quinine sulphate, 372 
INDEX 

Geitel 
natural conductivity of air in closed 
vessels, 351, 373 
Geitel and Elster 
radio-active lead, 25 
effect of magnetic field on conducti- 
vity produced by radium rays, 95 
scintillations produced by active sub- 
stances, 127 : 
action of radium rays on spark, 171 
photo-electric action of bodies co- 
loured by radium rays, 174 
radio-active matter in earth, 345 
discovery of radio-active matter in 
atmosphere, 351 
emanations from the earth, 357 
radio-activity of air in caves, 362 
radio-activity of the soil, 362 
radio-activity of natural carbonic acid, 
364 
variation of radio-activity of air, with 
meteorological conditions, 364 et seq. 
effect of temperature and pressure on 
radio-activity in atmosphere, 365 
Giesel 
coloration of bunsen flame by radium, 
15 
separation of radium bycrystallization 
of bromide, 15 
emanating substance, 23 
radio-active lead, 26 
magnetic deviation of B rays, 95 
temperature of radium bromide above 
air, 159 
decrease with time of luminosity of 
radio-active screen, 168 
coloration of bodies by radium rays, 
174 
evolution of gases from radium, 176 
action of radium rays on eye, 177 
emanation from the emanating sub- 
stance, 209 
luminosity produced by radium ema- 
nation, 209 
excited activity 
substance, 287 
bismuth made active by radio-active 
solution, 289 
activity of radium dependent on age, 
300 
Glass 
coloration produced in, by radium 
rays, 174 
phosphorescence produced by emana- 
tion, 210 
Globulin 
action of radium rays on, 175 
Goldstein 
canal strahlen, 92 
coloration of bodies byradium rays, 174 
from emanating 
