3. Glasses may be prepared of the correct tint for any fraction or multiple of this dose up to 2 B or 10 H. 4. Either daylight or electric light can be used. 5. The optical instrument itself, by cutting off extraneous light, greatly assists the colour comparisons, so that the practical error need never exceed 10 per cent. INDEX Abnormal light, 13 Analysis of white light, 11, 13 Arbitrary scales, 9 Artists and scientists, 1, 2 Beam of white light, 7, 11 Black units, 16, 23 Black, ideal, 15, 11 Blood curves, 33 Code of laws, 7 Colour charts, 31, 39 education, 59 equivalence, 10 nomenclature, 17, 21 qualitative, 17, 19, 24 quantitative, 24 scales, 20, 29 standardization, 20, 69 theories, 2, 3 Coloured surfaces, 44 Colours, complex, 18 sadder than standards, 25 simple, 17 Corbett, Dr. Dudley’s, radiometer, 83 Daylight colours, 24, 84 measurement, 14 Diffused light, 10, 43 Direct lights, 46 Dulled colour, 10, 18-26, 36 Equivalent colour units, 7, 9, 29 Fog, whiteness of, 10 Glass standards, 20 Human blood curves, 82 Laws of colour, 7 Light, 11, 13, 42, 45-46, 81-84 abnormal, 8 brighter than standards, 14, 27 direct, 46 for colour work, 42 intensities, 42, 43 white, 14 Lovibond’s new colour theory, 5 Matching colours brighter than standards, 18 complex colours, 17 Measuring and naming colours, 21 Monochromes, 17, 19 Munro, Dr., 34 Neutral tint, 18, 24, 26 North light, 15 Past theories, 3 Photographic energies, 53 Physical colour constants, 8 Pigmentary black, 15, 71 Primary colours, 1 Prismatic spectrum colours, 29 Qualitative analysis of colour, 17, 19, 24 Quantitative analysis of colour, 24 Radiometer, 83 Rate of colour absorption, 8 Rays, six colour, 7 Red ray, 41 Scales, arbitrary colour, 9 coloured, 10, 20 cross checking of, 9 Scientists and artists, 1, 2 Sea fog, 10 Specific colour, 32 Spectrum colours, 4, 18, 36 Three colours, 10, 57 Time, appreciation of colour by, 42 Ultra violet, 32, 40 Unit, checking of, 9 Unit, neutral tint, 18, 24, 26 Wave length position, 37, 38 White light, 11, 13 Butler & Tanner Frome and London Transcriber’s notes: In the text version, italics are represented by _underscores_, and bold and black letter text by =equals= symbols. Superscripts are represented by ^{} and subscripts by _{} Missing or incorrect punctuation has been repaired. Inconsistent spelling and hyphenation have been left, In the html version, dittos have been replaced by the repeated text so that text aligns for easier reading. Very wide tables (V and VI and VII)have been split to fit on portrait oriented pages. The following mistakes have been noted: