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 phenomena which are elaborately explained in a book entitled "The principles of Harmony and Contrasts of Colours" by M. Chevreul. The first edition of this book was prepared in 1835 and published in 1838. The author had at that time been employed for a number of years as superintendent of the manufactory of Gobelin Tapestries in Paris under the control of the French government.

In this book are described in detail the results of a great number of experiments which were instigated by complaints regarding certain colors produced in the dyeing department of the manufactory, and which afford the most elaborate exposition of the subject ever published.

One of the first things which led Chevreul to make his investigation was the complaint that certain black yarns used as shades in blue draperies were not a full black but more or less gray.

The author says in his preface, "The work I now publish is the result of my researches on Simultaneous Contrasts of Colours; researches which have been greatly extended since the lectures I gave on this subject at the institute on the 7th April, 1828. In reflecting on the relations these facts have together, in seeking the principle of which they are the consequence, I have been led to the discovery of the one which I have named the Law of Simultaneous Contrast of Colours."

The closing sentence of the preface to the first edition and dated 1835 is as follows:—

"I beg the reader never to forget when it is asserted of the phenomena of simultaneous contrast, that one colour placed beside another receives such a modification from it, that this manner of speaking does not mean that two colours, or rather the two material objects that present them to us, have a mutual