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PAINTERS' COLOURS, OILS,

AND VARNISHES.

CHAPTER I.

INTRODUCTORY.

COLOUR, COLOURS, PAINTS, AND VARNISHES. Colour is a term used by persons in several senses; hence confusion sometimes arises, although, as a rule, the context leaves no doubt as to the particular sense intended. When a beam of white light is made to pass through an angle of a triangular prism in a certain manner, and the light which has passed through is received upon a screen, we find that it has undergone a wonderful change; instead of being one uniform colour, as it was originally, it is spread out into a band of many colours, of which seven can readily be distinguished-viz., red, orange, yellow, green, blue, indigo, and violet. We see these colours by the effect or sensation produced by their action on the retina of the eye; in a sense, therefore, these colours have an abstract existence only, we can see them by the eye, but we cannot handle them as we can a piece of cotton. When we speak of a red colour or a green colour, we use the term "colour" in an abstract sense to indicate the sensation which these colours create in our eyes. On the other hand, we often speak of coloured bodies (that is bodies which give the sensation of being coloured when we look at them) as "colours," especially when (as with vermilion, chrome yellow, emerald green, Prussian blue, and magenta) they can be used to impart colour to other bodies. In this way "colour" is used in a concrete sense to indicate

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