presented to it in reality. We turn our attention therefore, in the first place, to this harmonious juxtaposition.
809.
As a very simple means of comprehending the principle of this, the reader has only to imagine a moveable diametrical index in the colorific circle.56 The index, as it revolves round the whole circle, indicates at its two extremes the complemental colours, which, after all, may be reduced to three contrasts.
810.
Yellow demands Red-blue,
Blue demands Red-yellow,
Red demands Green,
and contrariwise.
811.
In proportion as one end of the supposed index deviates from the central intensity of the colours, arranged as they are in the natural order, so the opposite end changes its place in the contrasted gradation, and by such a simple contrivance the complemental colours may