Turning for the moment from the results of actual experiment to outside criticisms, it has been asserted that one difficulty with which colour-music has to deal is, that the eye is incapable of appreciating changes of colour as rapid as the changes of tone which occur in music. If this were so, it would merely be an argument against the direct translation of rapid sound-music compositions into colour-music. The art of mobile colour does not, however, make such translations or adaptations one of its chief objects, and it might, in fact, abandon them altogether and yet leave its main purposes untouched.
It is, moreover, demonstrable that, so far from the eye being unable to appreciate changes as rapid as those which the ear can follow, its capacity is much greater in this respect. In photography it is found impossible to design a shutter so rapid in its action as to enable the most sensitive photographic plate to seize the image of some very rapidly moving bodies. These are therefore sometimes exposed in the dark, and illuminated for an infinitesimal portion of
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