INDEX. 
The numbers refer to the pages. 
a rays 
discovery of, 115 et seq. 
nature of, 115 et seq. 
magnetic deviation of, 117 et seq. 
electrostatic deviation of, 121 
velocity of, 122 et seq. 
value of e/m for, 122 
mass and energy of, 125 et seq. 
origin of, in atomic disintegration, 126 
scintillations produced by, 127 
absorption of, by matter, 129 et seq. 
increase of absorption with thickness 
of matter traversed, 129 et seq. 
relative absorption of a rays from 
radio-elements, 132 
absorption of, by gases, 133 
connection between absorption and 
density, 137 
relation between ionization and ab- 
sorption, 138 
theory of absorption of, 138 
effect of thickness of layer of radiating 
matter on emission of, 149 
relative ionization produced by a and 
B rays, 149 
relative energy emitted in form of a 
and 6 rays, 150 et seq. 
number and energy of a particles 
from radio-elements, 154 
emission of energy from radio-ele- 
ments in form of a rays, 154 
connection of heat emission of radium 
with a rays, 160 et seq. 
connection of, with radio-active 
changes, 193, 322 
from the emanations, 222 
absence of, in change in emanation 
X of thorium, 270 et seq. 
absence of, in change in emanation 
X of radium, 273 
non-separable activity of radio-ele- 
ments consists of, 304 
emission from all active products 
except last change, 304 
a particles consist of helium, 331 
loss of weight due to expulsion of, 335 
Abraham 
apparent mass of moving charged 
body, 109 
Absorption 
law of, in gases, 56 et seq. 
relative absorption of a, B and y rays 
by matter, 93 
of 8 rays by solids, 112 et seq. 
of a rays by solids, 129 et seq. 
of y rays by solids, 142 
connection between absorption and 
density for 8 rays, 113 et seq. 
connection between absorption and 
density for a rays, 137 
connection between absorption and 
density for y rays, 143 
of 6 rays in radio-active matter, 115 
of a rays in gases, 133 et seq. 
connection between absorption and 
ionization, 138 
theory of, 138 
of a rays by radium, 164 
of rays from the emanations, 222 
of penetrating rays from the earth, 367 
Actinium 
methods of separation of, 22 et seq. 
properties of, 23 
similarity to ‘‘emanating substance ” 
of Giesel, 24 
possible connection with radio-activity 
of thorium, 25 
emanation from, 208 
excited activity produced by, 288 
effect of magnetic field on excited 
activity from, 288 
Adams 
decay of activity of emanation from 
well water, 361 
decay of excited activity from the 
emanation, 361 
Age 
of radium, 333 
of sun and earth, 343 
Allan 
increase with time of excited activity 
from atmosphere, 355 
