INDEX 
Walker, G. W. 
theory of electrometer, 75 
Walkhott 
action of radium rays on skin, 176 
Wallstabe 
diffusion of radium emanation into 
liquids, 235 
Water 
emanation from, 360 
decay of activity of emanation from, 
361 
Water-falls 
amount of excited activity produced 
at Niagara, 366 
electrification produced near, 366 
Waits, Marshall 
atomic weight of radium, 17 
Weight 
loss of by radio-elements, 335 
attempts’ to measure loss of, in 
radium, 336 
Wheeler and Bumstead 
emanation from surface water and 
the soil, 361, 368 
identity of emanation from soil with 
radium emanation, 361 
absence of emanation in mercury, 
381 
Whetham 
effect of valency of ion on colloidal 
solutions, 175 
possible cause of disintegration of 
atom, 342 
Wiedemann and Schmidt 
thermo-luminescence, 170 
Wiedemann 
thermo-luminescence 
radium rays, 170 
Wien 
amount of charge carried by radium 
rays, 105 
positive charge of canal rays, 125 
produced by 
399 
Willcock, Miss, and Hardy 
coloration of iodoform solution by 
radium rays, 175 
Willemite 
phosphorescence of under radium 
rays, 168 
use to show condensation of emana- 
tion, 237 
Wilson, W. E. 
radium in sun, 342 
Wilson, H. A. 
charge on ion, 48 
Wilson, C. T. R. 
ions as nuclei of condensation, 44 
et seq. 
difference between positive and nega- 
tive ions as condensation nuclei, 46 
equality of charges carried by positive 
and negative ions, 47 
construction of electroscope, 73 
natural ionization of air in vessels, 351 
radio-activity of rain and snow,355,356 
loss of charge in closed vessels, 373 
presence of ions in free air shown by 
condensation, 375 
number of ions produced per ¢.c., 375 
effect of pressure and nature of gas 
on ionization in sealed vessels, 376 
Zeleny 
velocity of ions, 39 et seq. 
difference of velocity of ions, 40, 42 
potential gradient between electrodes, 
63 
Zerban and Hofmann 
active substances from pitchblende, 25 
Zine Sulphide 
scintillations produced in by a rays, 
127 
cause of luminosity of, 127 et seq. 
scintillations due to cleavage of 
crystals, 128 
CAMBRIDGE: PRINTED BY J. AND C, F. CLAY, AT THE UNIVERSITY PRESS. 
