COLOUR VISION [Illustration: TYPES OF COLOUR VISION. W. DE W. A., DEL. W. GRIGGS, LITH. ] COLOUR VISION BEING THE TYNDALL LECTURES DELIVERED IN 1894 AT _THE ROYAL INSTITUTION_ BY CAPT. W. DE W. ABNEY, C.B., D.C.L., F.R.S., LATE ROYAL ENGINEERS WITH COLOURED PLATE AND NUMEROUS DIAGRAMS NEW YORK WILLIAM WOOD AND COMPANY CONTENTS. PAGE PREFACE vii CHAPTER I. The Eye 1 CHAPTER II. Simple Colours and their Mixture 15 CHAPTER III. Three Colour Sensations Possible 32 CHAPTER IV. The Young and Hering Theories of Colour Vision 41 CHAPTER V. General Aspect of Colour Blindness 58 CHAPTER VI. Colour Blindness exhibited by Colour Discs and exhibited by Luminosity Curves of the Spectrum 74 CHAPTER VII. Luminosity of Colours to Different Parts of the Retina 88 CHAPTER VIII. Luminosity of a Feeble Spectrum and the Limit of the Perception of Colour 98 CHAPTER IX. The Extinction of Light from the Spectrum 108 CHAPTER X. The Extinction of the Perception of Light by the Colour Blind 122 CHAPTER XI. Tobacco Blindness 137 CHAPTER XII. Examples of Colour Blindness due to Disease 148 CHAPTER XIII. The Holmgren Test for Colour Blindness 167 CHAPTER XIV. The Spectrum Test for Colour Blindness 180 CHAPTER XV. The Young and Hering Theories of Colour Vision Compared 187 APPENDIX 201 INDEX 229 PREFACE. The writer had for some years past, in conjunction with General Festing, and recently as Secretary and Member of the Colour Vision Committee of the Royal Society, carried out a series of investigations on colour vision, and selected that subject when he was invited, in 1894, to deliver the Tyndall Lectures at the Royal Institution.