of quick-passing concrete images, to shock, to startle, or to charm—­but as a rich and various language in which light, proverbially the symbol of the spirit, is made to speak, through the senses, some healing message to the soul.  For such a consummation, “devoutly to be wished,” natural forms—­forms abounding in every kind of association with that world of materiality from which we would escape—­are out of place; recourse must be had rather to abstract forms, that is, geometrical figures.  And because the more remote these are from the things of sense, from knowledge and experience, the projected figures of four-dimensional geometry would lend themselves to these uses with an especial grace.  Color without form is as a soul without a body; yet the body of light must be without any taint of materiality.  Four-dimensional forms are as immaterial as anything that could be imagined and they could be made to serve the useful purpose of separating colors one from another, as lead lines do in old cathedral windows, than which nothing more beautiful has ever been devised.

Coming now to the consideration, not of differences, but similarities, it is clear that a correspondence can be established between the colors of the spectrum and the notes of a musical scale.  That is, the spectrum, considered as the analogue of a musical octave can be subdivided into twelve colors which may be representative of the musical chromatic scale of twelve semi-tones:  the very word, chromatic, being suggestive of such a correspondence between sound and light.  The red end of the spectrum would naturally relate to the low notes of the musical scale, and the violet end to the high, by reason of the relative rapidity of vibration in each case; for the octave of a musical note sets the air vibrating twice as rapidly as does the note itself, and roughly speaking, the same is true of the end colors of the spectrum with relation to the ether.

But assuming that a color scale can be established which would yield a color correlative to any musical note or chord, there still remains the matter of values to be dealt with.  In the musical scale there is a practical equality of values:  one note is as potent as another.  In a color scale, on the other hand, each note (taken at its greatest intensity) has a positive value of its own, and they are all different.  These values have no musical correlatives, they belong to color per se.  Every colorist knows that the whole secret of beauty and brilliance dwells in a proper understanding and adjustment of values, and music is powerless to help him here.  Let us therefore defer the discussion of this musical parallel, which is full of pitfalls, until we have made some examination into such simple emotional reactions as color can be discovered to yield.  The musical art began from the emotional response to certain simple tones and combinations, and the delight of the ear in their repetition and variation.