CHAPTER I.
Introduction.
It may at first appear strange that colour, one of the most important indices of value in the Arts, Manufactures, and Natural Products, should have no common nomenclature or reliable standard for reference, the reproduction of a given colour depending for exactitude on the memory of a sensation; whereas this branch of science requires a physical means of recording a colour, with a power of recovery. It remains to be shown that this power of record and recovery is possible, and depends only on the observance of a few simple natural laws easy of application.
The study of colour is carried on by two principal methods: the spectroscopic, where the colours are partially separated as a continuous band by a regular variation in their indices of refraction, the colours gradually merging into each other by overlapping in opposite directions; or by absorption, where a colour is developed by absorbing its complementary, and is isolated as a single or complex colour. This latter is nature’s own method.
It is necessary to touch on some theoretical differences which exist between Scientists and Artists, as to which are Primary colours, as confusion of this character retards investigation. Scientists adopt Red, Green, and Violet as Primaries, regarding all other colours as mixtures of these; whilst Artists and Colourists adopt Red, Yellow and Blue as the Primaries, and all other colours as made from them.
The theory of the Scientists is based on the phenomena developed by mixing coloured lights taken from different parts of the spectrum. This is a method of synthesis, each added colour being a progressive stage towards the complexity of white light. In this case the colour developed is that of the preponderating ray of a complex beam. The theory of the Artists is based on the phenomena developed by mixed pigments. This is a method of analysis, tending towards ray simplicity, each added pigment reducing the complexity of the colour developed by its power of selective absorption.
The theoretical differences between the two schools appear to have arisen from supposing that a given colour developed by the two methods should correspond; but considering the differences in their ray composition, this would be impossible, for although both may be describable by one general colour term, as for instance a Red, they would be of two varieties. It remains to be shown that one theory may cover both sets of phenomena.