"You will find that this experiment will instruct you, not only in the principles of light and shade, but also of colours; for that there is a corresponding hue with respect to colours is not to be disputed. In order to demonstrate this, place in the ball which you have illuminated, the prismatic colours, suiting their hues to those of the tints. Yellow will answer to the focus of illumination, and the other secondary and primary hues will fall into their proper places. Hence, on the enlightened side of a group or figure, you may lay yellow, orange, red, and then violet, but never on the side where the light recedes. On that side must come the other prismatic colours in their natural order. Yellow must pass to green, the green to blue, and the blue to purple. The primary colours of yellow, orange, and red, are the warm colours, and belong to the illuminated side of objects; the violet is the intermediate, and green, blue, and purple are the cold colours, and belong to the retiring parts of your composition. "On the same principle, and in the same order, must be placed the tints which compose the fleshy bodies of men and women, but so blended with each other, as to give the softness appropriate to the luminous quality and texture of flesh; paying attention, at the same time, to reflections on its surface from other objects, and to its participation of their colours. The latter is a distinct circumstance arising from accident. "When the sun illuminates a human body, in the same manner as the ball, the focus of the illumination in that body will partake of the yellow; and the luminous or transparent tint, will have the orange and the red. These produce, what is called, the carnation. The pure red, occasioned by the blood, lies in the lips, cheeks, joints, and extremities of the figure, and no where else. On the receding side of the focus is the local colour of the flesh, and on the receding side of that is the greenish tint; in the shade will fall the cold or bluish, and in the reflection will fall the tint of purple. The most perfect tint of ground, from which to relieve this arrangement of colours, is either blue, grey, or purple, for those colours partake of the complexion of the watery sky in which the rainbow appears, or the ground which best exhibits the prismatic colours. "In acquiring a practical knowledge of the happiest manner of distributing your colours according to nature, it will assist you, if you will copy with attention some pieces of Titian, Correggio, Reubens, and Vandyke; the masters in whose works you will most eminently find the system pursued, which I have endeavoured to illustrate by the simple image of the ball.