404 
INDEX 
Density of stars, 5, 8; ratio of central to 
mean density, 84 ; mean densities of stars, 
'136; high density possible, 170 
Destruction of matter, 293 
Detailed balancing, principle of, 45 
Deviations from perfect gas, 260; in ionised 
gas, 263; in stars, 131, 165 
Diameter. See Radius 
Dielectric constant, 237 
Diffuse matter in space, 371 
Diffuse nebulae, 387 
Diffusion, coefficient of, 277; thermal, 276; 
of electrons, 273 
Dilution, factor of, 382 
Disorganisation of energy, 30 
Displacement law (Wien’s), 39 
Dissipation of energy in Cepheids, 198 
Distribution, of elements in a star, 275, 298; 
of subatomic sources, 122 
Dootson, F. W., 277 
Double stars. See Binary stars 
Doublets, 74 
Douglas, A. V., 307 
Duration of stages of evolution, 309 
Dwarf stars, 7, 130; white dwarfs, 170 
Dynamical parallaxes, 158, 161 
Earth, age of, 290 
Eclipsing variables, 156, 208 
Effective temperature, of radiation, 37 ; of a 
star, 2, 120, 135, 140, 323; of radiation in 
space, 371 
Eggert, J., 346, 399 
Einstein’s equation, 46, 56 
Einstein’s theory of gravitation, 6, 172; 
identity of mass and energy, 294 
Electric charge in a star, 272 
Electrons, 10; orbits of, 58; K and L groups, 
69; capture of, 24, 218, 221, 230, 245; 
scattering by, 74, 77, 316, 385; free, 64, 
263; runaway, 302; destruction of, 293 
Electrostatic energy and pressure, 264; cor 
rection to ionisation, 257 
Elements, atomic numbers and energy levels 
of, 252; stellar abundance of, 369 
Emden, R., 5, 81 
Emission coefficient, 24, 47, 218, 329; re 
lation to absorption coefficient, 50, 54, 
105; theories of, 223, 229, 245 
Emission lines, 343 
Enclosure, 35, 39, 100 
Energy, of a polytrope, 86; of a star, 141; 
of a white dwarf, 172; of the sun, 289, 292; 
of ionisation, 269 
Energy, subatomic, 292 
Energy and mass, 27, 294 
Energy levels in atoms, 252, 257 
Energy-density of equilibrium radiation, 38; 
relation to pressure, 29 
Enhanced Unes, 345 
Enskog, D., 277 
Entropy, 30 
Equilibrium of a star, 9, 79; stability of, 142 
Equilibrium radiation, 36 
66 Eridani, 380 
Escape of atoms, 368, 392 
Evenly diluted radiation, 376, 382 
Evershed, J., 362 
Evolution of stars, 7, 174, 296, 309 
Exchanges, principle of, 35, 45 
Excited atoms, 45, 66, 238, 259, 346 ; life of, 
364 
Excluded volumes, 259 
Exhaustion of subatomic sources, 297, 299 
Fabry, C., 330, 371 
Fixed calcium lines, 377 
Flow of heat, 100, 321; variable, 197 
Fowler, A., 73, 345 
Fowler, R. H., 194, 220, 256, 266, 347. 379 
Free electrons, 64, 263 
Free path, 222, 277, 280, 368, 373 
Frequency. See Wave-length 
Gas, deviations from perfect, 131,165;theory 
of, 260, 263 
Gas-constant, 8 
Gas-sphere, 79; polytropic, 80; isothermal, 
89; tables, 82, 90 
Gerasimovic, B., 286 
Giant and Dwarf theory, 2, 119, 163 
Giant stars, 5, 176; masses of, 307; lower 
effective temperature, 361 
Gravitation opposed by radiation pressure, 
17 
Gravity on Capella, 15; on the sun, 395 
Guggenheim, E. A., 256, 266 
Guillotine, 231, 256; factors, 233 
Güssow, M., 181 
Gyllenberg, W., 207 
Hamiltonian equations, 59, 67 
Hartree, D. R., 257 
Heat, aetherial and material, 19; irreversible 
flow of, 32; radiometer measurement of, 
138, 206; sun’s store of, 289 
Helium, formation of, 292, 296, 301, 314, 
315, 317 
Helmholtz, H. L. F., 289 
Hertzsprung, E., 7, 139, 152, 158, 161, 164, 
180, 290, 310 
Hubble’s variable nebula, 387 
Hyades, 158 
Hydrogen, exceptional behaviour of, 10, 244, 
276, 315; quantisation of, 58; trans 
mutation of, 293, 296, 301, 314 
Hypothetical parallaxes, 158, 161 
Initial temperature of electron gas, 376 
Inner quantum number, 74 
Inside of a star, 19 
Insight, 102 
Interferometer, 6, 12, 171 
Interstellar space, 371 ; calcium cloud in, 378 
Invariance of weights, 68 
Inverse square forces, 168