Yellow

Abstract

IT would seem to me that the great difficulty of conceiving yellow as a compound colour is the brightness or lightness of yellow, as compared with its components. In the spectrum, we have the maximum of light in the yellow, and it is against our experience to put two dark colours together and form one light one, as, for example, to put the red and green together and form yellow. But there is just the same difficulty in the production of white light from all the colours of the spectrum, for we regard white as lighter than any of the colours, even than yellow. This, however, is a mental fallacy, and if once exposed, seems to me to do away with the difficulty of conceiving white as made up of a series of colours. Our ideas of colours and tints are derived from our own experience, and we produce tints by precisely the opposite method to that of nature. Nature's method of painting a blade of grass is, to throw on it all the colours of the spectrum, and afterwards pick out those which shall have a residue of green. The artist's method is to see what colours will produce green and then lay those on. I do not think it too much to say that all colours are merely tints of white—that, for example, yellow is really yellowish white, green, greenish white, and so on. If we take two cards, one green, the other red, and hold them so that the light is properly reflected from the one on to the other, the cards do not appear black but white. If the red and green were pure colours, the cards should of course appear black, for the light from the green card would be totally absorbed by the red card, and similarly with the red card. The white cannot be produced by a combination of the red and green, but by the extinction on one card of the green that gives the greenish white, and on the other of the red which gives the reddish white. That yellow is but little different from white is well illustrated in the beautiful experiment of Newton's of synthesising the colours of the spectrum by reflection from seven moveable mirrors. With the mirrors placed at equal distances from each other, the spot of compound light is not white but yellow, that is to say, it is yellowish white, the colours lost between the mirrors being just those necessary to bring out the full white.