CONTENTS.

[CHAPTER I.]

Sources of Light—Reflected Light—Reflection from Roughened Surfaces—Colour Constants p. 11

[CHAPTER II.]

A Standard of Light—Formation of the Spectrum by Prisms and by the Diffraction Grating—Wave-lengths of the principal Fraunhofer Line—Position of Colours in the Spectrum p. 17

[CHAPTER III.]

The Visible and Invisible Parts of the Spectrum—Methods for showing the Existence of the Invisible Portions—Phosphorescence—Photography of the Dark Rays—Thermo-Electric Currents p. 30

[CHAPTER IV.]

Description of Colour Patch Apparatus—Rotating Sectors—Method of making a Scale for the Spectrum p. 41

[CHAPTER V.]

Absorption of the Spectrum—Analysis of Colour—Vibrations of Rays—Absorption by Pigments—Phosphorescence—Interference p. 51

[CHAPTER VI.]

Scattered Light—Sunset Colours—Law of the Scattering by Fine Particles—Sunset Clouds—Luminosities of Sunlight at different Altitudes of the Sun p. 62

[CHAPTER VII.]

Luminosity of the Spectrum to Normal-eyed and Colour-blind Persons—Method of determining the Luminosity of Pigments—Addition of one Luminosity to another p. 76

[CHAPTER VIII.]

Methods of Measuring the Intensity of the Different Colours of the Spectrum, reflected from Pigmented Surfaces—Templates for the Spectrum p. 88

[CHAPTER IX.]

Colour Mixtures—Yellow Spot in the Eye—Comparison of Different Lights—Simple Colours by Mixing Simple Colours—Yellow and Blue from White p. 112

[CHAPTER X.]

Extinction of Colour by White Light—Extinction of White Light by Colour p. 126

[CHAPTER XI.]

Primary Colours—Molecular Swings—Colour Sensations—Sensations absent in the Colour-blind p. 133

[CHAPTER XII.]

Formation of Colour Equations—Kœnig's Curves—Maxwell's Apparatus and Curves p. 147

[CHAPTER XIII.]

Match of Compound Colours with Simple Colours—All Colours reduced to Numbers—Method of Matching a Colour with a Spectrum Colour and White Light p. 156

[CHAPTER XIV.]

Complementary Colours—Complementary Pigment Colours—Measurement of Complementary Colours p. 167

[CHAPTER XV.]

Persistence of Images on the Retina—The Use of Coloured Discs p. 179

[CHAPTER XVI.]

Contrast Colours—Measurement of Contrast Colours—Fatigue of the Eye—After-Images p. 196