INDEX.

Absorption by red, blue, and green glasses,53

Absorption of light in the earth's atmosphere, 67

Absorption, reference to law of,53

After-glow,74

Arc light,20

Artists and colours, 195

Balmain's paint,33

Black body,18

Blindness to green, 142

Blindness to red,79-142

Bromo-iodide of silver,136

Carbon poles,20

Carmine, light reflected from, 107

" template,106

Chlorophyll, green solution of,51

Collimating lens, focal length of,22

Colour, analysis of,52

Colour-blind, red and green,79 , 80

Colour-blindness,142-146, 157 , 159

Colour constants,15

Colour equations, formation of,147 , 148

Colour, extinction of, by white light,126

Colour mixtures,113

Colour patch apparatus,41-52

Colour sensation of the eye,202

Coloured discs, use of,189

Coloured glasses, measurement of,162

Colours, complementary of pigments,170-172

Colours, complementary of spectrum,167

Colours, how matched,156 , 157

Complementary colours, measurement of,173-178

Compound colours, definition of,16

Continuous spectrum,17

Contrast colours,196-200

Diffraction gratings,23

" spectra,24

Dimness and brightness of spectrum,29

Discs, spinning,182

Dust, particles of,62

Electric light, contrast colours in,197

Electric light, crater of positive pole of,20

Emerald green, light reflected from,94

Equations, colour,147

Essentials of spectrum,22

Extraction of colour by white light,126

Extraction of white light by colour,131

Eye, sensitiveness of,15

Fatigue of the retina,202

Fluorescence,31

Fundamental sensations,140

Gamboge, matching,189

Glass, light from sheet of,14

Glass prisms,21 , 22

Glow-worm,13

Green colour-blindness,142

Heating effect of radiation,38

Hue,15

Images, after,202

Images, persistence of, on retina,179

Impurity of simple colours,124

Indicator of sectors,48

Infra-red rays,32

" photography with,34

Insensitiveness of the yellow spot to green,118

Intensities of limelight, gaslight, and blue sky compared,110 , 121

Interference,58 , 59

Interference bands on soap film,60

Invisible spectrum, methods for showing existence of,32 , 33

Kœnig's curves,151

Kœnig's experiments,140

Law of the scattering by fine particles,66

Light from sun, imitation of,63

Light, quality of, illumining object,14

Light scattered,62

Limelight,19

Lines in solar spectrum,26

Luminosity,13

Luminosity, addition of one to another,85-87

Luminosity of colour,16

Luminosity of pigments, methods of determining,81 , 82

Luminosity of spectrum to normal-eyed and colour-blind persons,76-78

Luminosity of sun at different altitudes,69-71

Maxwell's colour-box,152 , 153

Maxwell's discs,184-186

Measurement of amount of light reflected by different pigments,88-92

Metals, light reflected from,100

Mock suns, cause of change of colour in,64

Molecular physics,54

Molecular swings,136 , 137

Monochromatic light,47

Negative images,203

Normal vision,77

Orange, finding luminosity of,190

Percentages of skylight, sunlight, and gaslight,110 , 111

Phosphorescence,32 , 56

Pigments, absorption by,57 , 58

Plan of forming spectrum,21

Polished and uneven surfaces,13

Primary colours, definition of,133- 135

Prism, Iceland spar,96

Prismatic spectrum into wave-lengths, conversion of,28

Prisms, drawback to use of,23

Prussian blue template,107

" " light reflected from,107

Purity of colour,16

Rays, infra-red,34

Rays, photography of dark,34

Rays, ultra-violet,34

Registering tint of pigments,116

" " colours,156

Retina, persistence of images on,179

Ritter's rays,32

Rood's colour scale,26

Rotating sectors,46

Scaling of spectrum,49

Sectors, rotating,46

Simple colours, how obtained,112 , 113

Slits placed in spectrum,113

Soap-bubbles,58 , 59

Soap-films,59

Spectrum, absorption of,51 , 52

Spectrum of sunlight,18

Sun, mock,64

Sunset clouds,68 , 69 , 72 , 73

Sunset sky,72 , 73

Thermopile, heating effects of,36

Thermopile, principle of,35

Ultramarine, light reflected from,95

Ultra-violet rays,31

Vermilion, light reflected from,93

Vibrations of rays per second,55

Violet bands, brightness of,21

Visible and invisible parts of spectrum,30

Water, particles of,62

Wave-length of lines in solar spectrum,26

White light and contrast colours,200-202

White light, extinction of by colour,131

White light, formation of by mixture of yellow and blue,125

White light, how made,114 , 115 , 119-123

White light, impression of,81

Yellow and blue make white,125

Yellow, chrome, luminosity of,191

Yellow spot,117

Young-Helmholtz theory,138

THE END.

Richard Clay & Sons, Limited, London & Bungay.