appreciable as such, if it is lighter than white and darker than black. It is, however, to be remarked, that the white surface round the light greenish image seems tinged with a reddish hue, and the black surface round the dark image becomes slightly illuminated with the same colour, thus in both cases assisting to render the image apparent (58).
The difficulty or impossibility of describing degrees of colour in words, has also had a tendency to mislead, by conveying the idea of more positive hues than the physiological contrast warrants. Thus, supposing scarlet to be relieved as a dark, the complemental colour is so light in degree and so faint in colour, that it should be called a pearly grey; whereas the theorists, looking at the quality of colour abstractedly, would call it a green-blue, and the diagram would falsely present such a hue equal in intensity to scarlet, or as nearly equal as possible.
Even the difference of mass which good taste requires may be suggested by the physiological phenomena, for unless the complemental image is suffered to fall on a surface precisely as near to the eye as that on which the original colour was displayed, it appears larger or smaller than the original object (22), and this in a rapidly increasing proportion. Lastly, the shape itself soon becomes changed (26).
That vivid colour demands the comparative absence of colour, either on a lighter or darker scale, as its contrast, may be inferred again from the fact that bright colourless objects produce strongly coloured