Angles, of reflection, 27; of total
reflection, 54; of polarisation, 222;
of bi-axial crystals, 319
Anomalous dispersion, 81, 85, 107;
in crystals, 314, 320
Apophyllite rings, 314
Apparatus, 1-21; polarising, 242;
for bi-axial crystals, 249, 316
Arragonite, conical refraction in, 324
Artificial quartz preparations, 303;
uni-axial crystals, 313, 329; Nicol
prisms, 257
Artists, mistakes of, 75, 121
Axes, optic, 226, 231, 325; relation
of, 326, 338
BALMAIN'S paint, 144
Balsam and bezol, for mounting, 264
Bands in spectrum of Newton's
rings, 172; mica, 173; selenite,
268; quartz, 286
Barton's buttons, 190
Becquerel on phosphorescence, 151
Bi-axial crystals, 231,315; apparatus
for exhibiting, 249, 316; theory of,
321
Biot's experiment on sonorous vibra-
tions, 278
Bi-quartz, 286, 288
Bi-sulphide prisms, 16, 84 -
Black surfaces, polarisation by, 346
Blue and yellow, variety of effects
from, 123
Brewster on the polarising angle,
223; his artificial crystals, 313
Brookite, peculiar dispersion of, 321
Brücke on polarisation by small
particles, 345
Bunsen's holder, 16
CALCITE, 208
Calorescence, 150
Camera obscura, 22
Care of calcite prisms, 252
Cascade, luminous, 55
Cauchy on dispersion, 108
Change in wave-length, 141
Chemistry, solar and stellar, 138
Chlorophyll, phenomena of, 114, 148
Chromatic aberration, 70
Circular double-refraction, 284, 292
Circular polarisation, 294; effects
on crystal figures, 333
Clock, polar, 344
Collimator, use of, 84
Colour, III; caused by suppression,
72, 112, 159; absorbed, reflected,
and transmitted, 114; only a
sensation, 118, 124
Colour-blindness, 127
Colours, not primary, 123; com-
plementary, 116; of thin films,
158; of thick plates, 207; of polar-
ised light, 260, 286
Combinations of mica and selenite,
328
Common light, theories of, 234
Complementary bands in spectrum
of polarised light, 268, 286
Complementary colours, 116, 260,
286
Composite crystals, 326
Composition, of colours, 71; of
vibrations, 295
Conical refraction, 324
Conservation of energy, 153
Continuous spectra, 131
Convergent rays in crystals, 309
Cord, displacement of, analogous to
light, 239
Cornu's saccharometer, 289
Crossed crystals, 328; mica films,
329
Crossing films, effects of, 266
Crova's disc, 96
Crystallisations, 269; on the screen,
273
Crystals, uni-axial, 226, 230; bi-
axial, 231, 315; rotatory, 290;
composite, 326; irregular, 327;
crossed, 328; rings and brushes
in, 308; in circular light, 333;
spirals in, 337
Crystal stage, 311
Cylindrical lens, 72
DE DOMINIS, experiment on the
rainbow, 78
Deflection of rays, 57
Delezenne's analyser, 207
Descartes on the rainbow, 80
Designs for polarised light, 263
Deviation, minimum, in prism, 59
Diagrams for lantern, 18
Diffraction, 182; spectra, 191; in
the microscope, 200
Direct vision prisms, 83
Direction of vibrations in polarisa-
tion, 224; in common light, 234
Disc, Crova's, 96; Newton's, 73
Dispersion, 66, 107
Dispersion, anomalous, 81, 85;
crystals, 314, 320
Dolbear's opheidoscope, 39
Doubled angle of reflection, 31
Double-image prisms, 209
Double refraction, 208; analysed,
Foucault's experiment on velocity of
light, 90; his prism, 251
Fox, on diffraction patterns, 185; on
mica preparations, 264, 305
Fraunhofer's lines, 132, 136
Fresnel, on transverse vibrations,
217, 235; his theory of common
light, 235; his mirrors, 178;
his prism, 179; his quartz
prism, 284; his rhomb, 295;
on quartz, 284; on rotatory
polarisation in fluids, 292
Fuchsine, anomalous dispersion of,
85
GASES, spectra of, 130; of in-
candescent, 133
Gas-burner in lantern, 4
Gas-regulators for lime-light, 9
Geological sections polarised, 273
Glass in sonorous vibration, 278
Glass piles, 215, 252
Goldleaf, colours of, 115
Gratings, 183
Green, not a compound, 118
Grey, nature of, 75
Gypsum, effects of heating, 321
HAMILTON on conical refraction,
324
Heat, effects of, 276, 322; identical
with light, 142, 350; its vibrations
visible, 33
Hemitrope crystals, 327
Herschel, on polarisation of the sky,
345; on reversal of phase in re-
flected light, 195; right and left
handed crystals, 284; on a
stretched cord, 241; on water-
colour painting, 121
Hoffman's arrangement for bi-axials,
317
Huyghens' construction of waves,
IOI; experiment, 210; on double
refraction, 217
Hyperbolic curves, 170, 328
Identity of light, heat, and actinism,
142, 350
Images, 22; from mirrors, 29, 41;
from lenses, 61; virtual, 28, 43, 62
Indices of refraction, 52, 230
Intensity, law of, 27
Interference, 154; conditions of, 158
Interference bands in spectrum, 172,
268, 286; in analysis, 282
Inverse squares, law of, 27
Inversion of images, 25, 42, 62
Invisibility, of polished surfaces, 45;
of light, 46
Invisible rays, 141
Iodide prism, 83
Irregular crystals, 327
Irregular refraction, 181
Isolating phenomena, need for, 24,
78, 173
Ivory balls as illustrating waves, 94
JAMIN'S prism, 257
Jellett's analyser, 289
KALEIDOPHONE, 37
Kaleidoscope, 31
Kundt on sonorous vibrations, 281
LANTERN, I; vertical attachment,
19; mounting, 12; diagrams, 18
Lantern polariscope, 4, 253
Lenses, 60; achromatic, 83; mount-
ing, 14
Light, for optical experiments, 4;
centering, II; invisible, 46; a
mode of motion, 91; theories of,
88, 91, 94
Lime-light, 6
Line spectra of gases, 133
Lines, Fraunhofer, 132, 136
Lines, thickened, 137
Lippich on common light, 238
Liquid waves, 155
Lissajous' experiment, 34
Lloyd on conical refraction, 324
Lockyer, on transmission of states,
93
Lommel on fluorescence, 148
Lycopodium, diffraction by, 186
MACH, on sonorous vibrations, 281
Magnesium light for fluorescence,
147
Magnetic rotation, 290
Matter, possibly vortices in the
ether, 355
Measurement, of wave-lengths, 192;
of molecules, 196
Mechanical illustrations, of undulat-
ory theory, 108; of polarisation,
219
Metals, reflection from, 299
Mica, bands in spectrum of, 173,
268; designs in, 263; artificial
uni-axial crystals of, 303, 329;
work with films, 305; quarter-
wave plates, 297; combinations
with selenite, 328
Microscope, bi-axials in the, 318;
diffraction in the, 200
Micro-slides, 250, 272
Mirrors, concave, 40; convex, 43;
reflecting, 37; Fresnel's, 178
Mistakes of artists, 75, 121; of the
eye, 118, 125
Mitscherlich's experiment, 226,322 ;
his saccharometer, 289
Mixed plates, 181
Mixtures of light and pigments, 118
Molecular constitution, 197, 291
Molecules, size of, 196
Mother-of-pearl, 188
Motion, light must be, 91; a form
of, 352; a revealer of, 152
Mounts for lenses, &c., 13
Multiple images, 29, 59
NARROW slit, need of, 77
Natural colours residual, 115
Nature and her Author, 354
Newton's experiment on the spec-
trum, 65; in total reflection, 67;
colour-disc, 74; rings 166; analysis
of, 170
Nicol prisms, 243; care of, 252;
artificial, 257
Nobert's gratings, 184, 197
Normal, the, in optics, 28
Norremberg's artificial mica-film
uni-axial crystals, 329; doubler,
255; lenses for bi-axials, 317;
mica and selenite combinations,
328
OBJECTIVE for optical lantern, 2
Oil-lamps, for lantern, 6
Opheidoscope, 39
Opposite rotations, 284
Optic axes, 226, 231, 325; relation
of, 326, 338
Organic substances, 273
Oxide, colours in film of, 160
Oxygen, for lime-light, 7
P. ANGULATUM, effects of, 204
Particles, small, as polarisers, 345
Pendulum, experiments with, 295
Perforated cards, experiments with,
186
Persistence of vision, 73
Phase, reversal of, 195, 262
Phoneidoscope, 174
Phosphorescence, 144
Pillar-stands for apparatus, 13
Pigments, mixtures of, 118
Pincette, tourmaline, 311
Plane of polarisation, direction of
vibrations in, 224
Plateau's soap solution, 162
Polar clock, 344
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