interweaving of opposing colours and the resultant effects of luminosity and other beautiful qualities, and also by the æsthetic emotions produced by contrasts into which the element of time enters. Just as in a picture a contrast is largely influenced by the relative size of contrasting colour patches, or, in other words, by the relative masses of colour, so in mobile colour contrast is greatly modified in its effects on the eye and mind by the length of time during which the contrasting colours remain upon the screen. If, for instance, it is flooded with a deep red for a second or two, and a short sharp note of sapphire-blue is then struck, the contrast will be greater than that produced by two brief notes of scarlet and blue of equal duration. A whole series of rapid notes of colour of equal length which are more or less in contrast to each other affect the colour-senses less strongly than the same colours in contrast with others when of longer duration upon the screen.
Of special interest also to artists is the introduction of the element of time into gradated effects of colour by means of mobile
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