Produced by Chris Curnow, Hazel Batey and the Online Distributed Proofreading Team at https://www.pgdp.net (This file was produced from images generously made available by The Internet Archive) This E text uses UTF-8 (unicode) file encoding. If the apostrophes, quotation marks and Greek text [ἀπολύτρωσις] in this paragraph appear as garbage, you may have an incompatible browser or unavailable fonts. First, make sure that your browser’s “character set” or “file encoding” is set to Unicode (UTF-8). You may also need to change the default font. Illustration: COLOUR-PATCH APPARATUS. _THE ROMANCE OF SCIENCE._ COLOUR MEASUREMENT AND MIXTURE. =With Numerous Illustrations.= BY CAPTAIN W. de W. ABNEY, C.B., R.E., D.C.L., F.R.S. PUBLISHED UNDER THE DIRECTION OF THE COMMITTEE OF GENERAL LITERATURE AND EDUCATION APPOINTED BY THE SOCIETY FOR PROMOTING CHRISTIAN KNOWLEDGE. SOCIETY FOR PROMOTING CHRISTIAN KNOWLEDGE. LONDON: NORTHUMBERLAND AVENUE, W.C.; 43, QUEEN VICTORIA STREET, E.C. BRIGHTON: 135, NORTH STREET. NEW YORK: E. & J. B. YOUNG & CO. 1891. PREFACE. Some ten years ago there were three measurements of the spectrum which I set myself to carry out; the last two, at all events, involving new methods of experimenting. The three measurements were: (1st) The heating effect; (2nd) the luminosity; and (3rd) the chemical effect on various salts, of the different rays of the spectrum. The task is now completed, and it was in carrying out the second part of it that General Festing, who joined me in the research, and myself were led into a wider study of colour than at first intended, as the apparatus we devised enabled us to carry out experiments which, whilst difficult under ordinary circumstances, became easy to make. On two occasions, at the invitation of the Society of Arts, I have delivered a short course of lectures on the subject of Colour, and naturally I chose to treat it from the point of view of our own methods of experimenting; and these lectures, expanded and modified, form the basis of the present volume. As a treatise it must necessarily be incomplete, as it scarcely touches on the history of the subject--a part which must always be of deep interest. The solely physiological aspect of colour has also been scarcely dealt with; that part which the physicist can submit to measurement being that which alone was practicable under the circumstances. W. De W. Abney. _South Kensington, 1st May, 1891._ 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.