The yellow and blue, in the first case (214), can by degrees meet so fully, that the two colours blend entirely in green, and the order will then be,
Yellow-red.
Green.
Blue-red.
In the second case (215), under similar circumstances, we see only
Blue.
Red.
Yellow.
This appearance is best exhibited by refracting the bars of a window when they are relieved on a grey sky.[4]
In all this we are never to forget that this appearance is not to be considered as a complete or final state, but always as a progressive, increasing, and, in many senses, controllable appearance. Thus we find that, by the negation of the above five conditions, it gradually decreases, and at last disappears altogether.