cal
quantities. No space will be given to such a relation because it is so
absurdly superficial; however, the language of music will be borrowed
with the understanding that no relation is assumed.

A few facts pertaining to vision will indicate the trend of developments
necessary in the presentation of mobile light. The visual process
synthesizes colors and at this point departs widely from the auditory
process. The sensation of white may be due to the synthesis of all the
spectral colors in the proportions in which they exist in noon sunlight
or it may be due to the synthesis of proper proportions of yellow and
blue, of red, green, and blue, of purple and green, and a vast array of
other combinations. A mixture of red and green lights may produce an
exact match for a pure yellow. Thus it is seen that the mixture of
lights will cause some difficulty. For example, the components of a
musical chord may be picked out one by one by the trained ear, but if
two or more colored lights are mixed they are merged completely and the
resultant color is generally quite different from any of the components.
In music of light, the components of color-chords must be kept
separated, for if they are intermingled like those of musical chords
they are indistinguishable. Therefore, the elements of harmony in mobile
light must be introduced by giving the components different spatial
positions.

The visual process is more sluggish than the auditory process; that is,
lights must succeed each other less rapidly than musical notes if they
are to be distinguished separately. The ear can follow the most rapid
execution of musical passages, but there is a tendency for colors to
blend if they follow one another rapidly. This critical frequency or
rate at which successive colors blend decreases with the brightness of
the components. If red and green are alternated at a rate exceeding the
critical frequency, a sensation of yellow will result; that is, neither
component will be distinguishable and a steady yellow or a yellow of
flickering brightness will be seen. The hues blend at a lower frequency
than the brightness components of colors; hence there may be a blend of
color which still flickers in brightness. Many weird results may be
obtained by varying the rate of succession of colors. If this rate is so
low that the colors do not tend to merge, they are much enriched by
successive contrast. It is known that juxtaposed colors generally enrich
one