to follow is, as far as it will take him, a fairly clear one. Physical facts as to the production of colour and of sound can, within certain limits, be definitely stated and compared. But when we come to the consideration of the effects of colour and of sound upon our eyes and ears, and through them upon our minds and emotions, upon memory and association, and upon those springs of suggestion and mental impulse which are so closely connected with art, we are in an altogether different domain and one within which there must necessarily be almost endlessly varied opinions.
Amongst scientific men we shall therefore not be surprised to find that some attach considerable weight to the analogy between the spectrum-band and the octave, and the action of colour and sound upon us mentally and emotionally; and that others attach very little and endeavour to confine themselves solely to the physical outlook. We may, perhaps, go as far as to say that valuable and helpful as is the opinion of men of science with regard to the latter, it is to those who have been trained to observe
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