as regards the plane of the picture. The direction of the light is attended to in like manner. This is considered to produce a gradation from side to side, while keeping has reference to depth, to the comparative distinctness of near and distant things.
871.
In proceeding to consider this subject, we assume that the painter is generally acquainted with our sketch of the theory of colours, and that he has made himself well acquainted with certain chapters and rubrics which especially concern him. He will thus be enabled to make use of theory as well as practice in recognising the principles of effect in nature, and in employing the means of art.
COLOUR IN GENERAL NATURE.
872.
The first indication of colour announces itself in nature together with the gradations