None
227 Hall effect, 434 Hefiier lamp, 81 ; emission o( 486 Helmholtz, 59 Hertz, 530 Hockin, sine law, 59 Hoeck, 470 Homocentric beam, 46 Huygens, 125; double refraction, 243 eyepiece, xoi; principle, 159, 179, 213 Illumination, intensity of; 79 Images, concept o^ 14; formed by coaxial surfaces, 17 Image space, 15 Incidence, angle o^ 3 ; plane o^ 3 ; prindpal angle o^ 362 Index of refraction, 3, 129; effect on temperature radiation, 502; by total reflection, 301 Interference, of light, 124; of polarized light, 247; by crystals in polarized light, 341; in absorbing biaxial crys- tals, 374; in absorbing uniaxial crys- tals, 380; ill crystals in convergent lig^t, 349; with laxige difference of path, 148. Interferometer, 144 Ions, 382: hypothesis of; 529; ratio of charge to mass, 447; radiation of, 535; vibrations of, damping of, 534 Isochromatic curves, 352 Isogyre, principal, 354 Isogyric, curves, 352 Jamin, 144 Katoptric systems^ 26 Kerr effect, 451 Ketteler, ether drift, 474 Kirchhoff, 169; inversion of spectral lines, 501; law of emission and ab- sorption, 496, 529, 542; consequences of Utw, 499 Kanig, 448 Kundt, anomalous dispersion, 394; nietal prisms, 357 INDEX 545 Lagrange, 321, 330 Langley, solar constant, 487, 516 Least time, law o^ 129; principle of, ii Lenses, 40; classification kA, 42; thin, 42 Limit of resolution of microscopes, 106 Lippmann, 157 Longitudinal waves, 259 Lorentz, moving media, 457, 481 Luminescence, 494, 529 Lummer, 79 Macalttso, 432 Mach, 146; anomalous dispersion, 394 Magnetically active substances, 418 Magnetic field, 262; energy of, 272; force, 262 ; rotation of the plane of po- larization, 426; dispersion in rotation of the plane of polarization, 429, 438 Magneto-optical properties of iron, nickel, and cobalt, 449 Magnification, angular, 22; in depth, 21; lateral, 19; of microscope, 104, 106; normal, 90; of telescopes, 108 Magnifying-glass, 95 Malus, 130; law of, ii Mascart, ether drift, 474 Maxwell, electromagnetic theory, 260; equations of electzomagnetic field, 264; fundamental assumption, 267 Meridional beam, 50 Metals, optical constants ol^ 366; dis- persion of, 396 Michelson, echelon, 228; ether drift, 478; interferometer, 149; limit of visibility, 540; velocity of light, 1 19; in water and carbon bisulphide, 120^ 123; in moving water, 446; visibility curves, 151; ^eman effect, 447 Microscope, 97 Neuhauss, 158 Neumann, elastic theory, 260; reflec- tion equations, 283 Newton, 125; rings, 136, 144, 148; in- tensi^ of rings, 302 Nicol prism, 244 Nodal points, 22 Normal surf&ce, 317 NOrremberg polariscope, 246 Objective, microscope, 98 Object space, 15 Opera-glass, Z09 Optical length oi the ray, 6 Optical systems, classifications of, 25 Orthoscopic points, 64 Qrthotomic system, 12 Paramagnetic, 269 Permeability, 269 ; equal to I for light- waves, 466 Phase, 126 Photographic systems, 93 Photography in natural colors, 156 Polariscope, NOrremberg, 246 Polarization, 243; by diflfraction, 205; circular, 249; elliptical, 249; ellipti- cal due to surface layer, 287; plane, 250; by tourmaline, 247; by pile of plates, 285; rotary, 400 Polarized light, partially, 253 Polarizer, 286 Polarizing angle, 246 Pouillet, solar constant, 487 Poynting, theorem, 273 Pressure of radiation, 488 Prevost, theory of exchanges, 491 Pringsheim, temperature. 