IX. Dioptrical Colours X. Dioptrical Colours of the First Class XI. Dioptrical Colours of the Second Class--Refraction Subjective Experiments XII. Refraction without the Appearance of Colour XIII. Conditions of the Appearance of Colour XIV. Conditions under which the Appearance of Colour increases XV. Explanation of the foregoing Phenomena XVI. Decrease of the Appearance of Colour XVII. Grey Objects displaced by Refraction XVIII. Coloured Objects displaced by Refraction XIX. Achromatism and Hyperchromatism XX. Advantages of Subjective Experiments-- Transition to the Objective Objective Experiments XXI. Refraction without the Appearance of Colour XXII. Conditions of the Appearance of Colour XXIII. Conditions of the Increase of Colour XXIV. Explanation of the foregoing Phenomena XXV. Decrease of the Appearance of Colour XXVI. Grey Objects XXVII. Coloured Objects XXVIII. Achromatism and Hyperchromatism XXIX. Combination of Subjective and Objective Experiments XXX. Transition XXXI. Catoptrical Colours XXXII. Paroptical Colours XXXIII. Epoptical Colours PART III. CHEMICAL COLOURS. XXXIV. Chemical Contrast XXXV. White XXXVI. Black XXXVII. First Excitation of Colour XXXVIII. Augmentation of Colour XXXIX. Culmination XL. Fluctuation XLI. Passage through the Whole Scale XLII. Inversion XLIII. Fixation XLIV. Intermixture, Real XLV. Intermixture, Apparent XLVI. Communication, Actual XLVII. Communication, Apparent XLVIII. Extraction XLIX. Nomenclature L. Minerals LI. Plants LII. Worms, Insects, Fishes LIII. Birds LIV. Mammalia and Human Beings LV. Physical and Chemical Effects of the Transmission of Light through Coloured Mediums LVI. Chemical Effect in Dioptrical Achromatism PART IV. GENERAL CHARACTERISTICS. The Facility with which Colour appears The Definite Nature of Colour Combination of the Two Principles Augmentation to Red Junction of the Two Augmented Extremes Completeness the Result of Variety in Colour Harmony of the Complete State Facility with which Colour may be made to tend either to the Plus or Minus side Evanescence of Colour Permanence of Colour PART V. RELATION TO OTHER PURSUITS.