INDEX 
405 
Ionisation, 10; equation determining, 65, 66; 
applied to stars, 251, 254; energy of, 142, 
269; in Cepheid variables, 204; in re 
versing layer, 345; in interstellar medium, 
382 
Ionisation potentials, 252, 257, 383 
Ions, size of, 166, 359; diffusion of, 273 
Iron, ionisation potentials of, 257 
Irreversible processes, 32 
Isothermal gas-sphere, 89, 92, 382 
Jeans, J. H., 3, 10, 203, 281, 287, 303, 312, 
322 
Joy, A. H., 160, 307 
K electrons, 23, 69, 217, 252 
Kelvin, 5, 289, 294 
Kohlhorster, W., 317 
Kohlschutter, A., 2, 342 
Kramers, H. A., 223, 225, 229 
Krueger 60, 150 
Kulenkampff, H., 234, 238, 249 
L electrons, 23, 69, 217, 252 
Lane, H., 4, 7, 163 
Laplace, 6 
Larmor, J., 294 
Leavitt, H. S., 181 
Light, absorption of, 383 
Light curve of variables, 147, 180, 205, 208, 
210 
Light ratio for 1 magnitude, 14 
Lindblad, B., 322, 325 
Lindemann, F. A., 10 
Line absorption and emission, 111, 238; 
formation of absorption lines, 337, 381; 
intensity of, 342, 350; width of, 353; 
emission lines, 343 
Lockyer, J. N., 6, 345 
Long period variables, 206 
Luminosity of stars, relation to mass, 151; 
relation to spectral type, 175; relation to 
period in Cepheids, 181; relation to heat 
radiation, 138 
Luminous efficiency, 13, 138, 213 
Magnetic field of star, 389 
Magnitude, 13, 14. See Absolute magnitude, 
Bolometric magnitude, Luminosity, Mass- 
luminosity relation 
Main series, 151, 176, 177, 210, 215, 299 
Mass, relation to energy, 27, 292, 294; dis 
tribution in a polytrope, 86; of chromo 
sphere, 368; of nebulae, 388 
Masses of stars, determined by radiation 
pressure, 16, 118, 308; method of de 
termining, 12; large masses, 148; initial 
masses, 307; change of, 176, 306, 312, 391; 
principal formulae involving, 135 
Mass-absorption coefficient, 22, 100 
Mass-luminosity relation, theory of, 116, 118, 
135; table of, 137; curve, 153; agreement 
with observation, 158; applied to Algol, 210 
Mass-ratios in binary stars, 160, 311 
Mathematicians, 102 
Maxwell’s equations, 57 
Maxwell’s law, proof of, 51; for electrons 
with negative energy, 64 
McDiarmid, R. J., 214 
McLaughlin, D. B., 214 
Merrill, P. W., 12, 207 
Metastable orbit, 74 
Michelson, A. A., 12 
Millikan, R. A., 318 
Milne, E. A., 287, 322, 325, 330, 347, 349, 
355, 361, 362 
Minimal problems (central pressure and 
temperature), 90 
Molecular weight, 10; probable values of, 
253, 258, 259; variation of, 128; deter 
mined by observation, 159; effect of 
change, 255 
Molecules, absorption by, 386 ; band spectra 
of, 350; quantisation of, 352 
Multiplets, 74 
Nebulae, 387; penetrating radiation from, 
319 
Nébulium, 389 
Negative absorption, 50 
Nernst, W., 3 
Newall, H. F., 10, 11 
Nicholson, S. B., 206 
Novae, 389 
Nuclear capture, 245 
Nucleus of atom, 10 
Opacity, 3, 21; distinguished from absorp 
tion, 109 ; inversely proportional to lumin 
osity, 118; astronomical measurement of, 
146; law of variation, 121, 219, 229, 237, 
248; variation with temperature, 202, 221, 
303 ; of dark nebulae, 388 
Optical depth, 321 
Optical spectra, 72 
Orbits of binary stars, 11; photometric 
orbits, 148, 209 
Orbits of electrons, 58, 71 ; of large quantum 
number, 61, 241 ; hyperbolic, 224, 229, 245 
Oscillation. See Pulsation 
Over-stability, 201, 299 
Pannekoek, A., 273, 388 
Parallax of Capella, 13; dynamical paral 
laxes, 158, 161 
Parsec, 395 
Pauli, W., 70, 76 
Payne, C. H„ 141, 369, 401 
Pease, F. G., 208 
85 Pegasi, 160 
Penetrating radiation, 317 
Perfect gas, 5, 8, 84, 116; deviations from, 
131, 167, 260, 263; of high density, 165 
Period of pulsation, 192 
Period-luminosity relation in Cepheids, 181 
Perrin, J., 296