Measurement of Color Mixtures. 
3 
demonstrated that thirty-six is the practicable limit, and 
accordingly that number has been adopted.* If the 
number of intermediate hues were equal in all cases 
there would, in this scheme, be five between each 
two adjacent fundamental colors of the spectrum; 
but a greater number of recognizably distinct hues is 
obviously necessary in some cases than in others; for 
example, spectrum orange is decidedly nearer in hue to 
red than to yellow, and therefore the number of inter¬ 
mediates required on each side of the orange is different, 
being in the proportion of four for the red-orange series 
to five for the orange-yellow, and similarly six are 
required for the violet-red series, while four suffice for 
the blue-violet hues. 
There is no known means by which we can measure 
the proportion of two or more pigments in any given 
mixture, “because color-effect cannot be measured by 
the pint of mixed paint or the ounce of dry pigment; ”f 
but, fortunately, we have a very exact method, in the 
color-wheel and Maxwell disks, by which the relative 
proportions of two or more colors in any mixture may be 
precisely measured. This method has been used in the 
painting of every one of the 1115 colors of the present 
work, by means of one disk to represent each one of the 
thirty-six colors (both pure and “broken”), together 
with a black, a white, and a neutral gray disk, the last 
being a match in color to the gray resulting from the 
mixture of red, green and violet on the color-wheel;! the 
neutral gray disk, however, being used only for the 
making of disks for the broken series of colors (', ", 
and and for the scale of neutral grays (Plate 
*That is to say, the practical limit for pictorial representation of the colors in 
itheir various modifications. 
fMilton Bradley: Elementary Color, p. 18. 
JSee colored figure on frontispiece. . 
