24 Color Standx\rds and Nomenclature. 



or broken. The difficulty is increased by the additional 

 fact that any black pigment mixed with almost any color 

 falls short of even the color-wheel mixture in purity of 

 hue in the resulting shades, owing to the very consider- 

 able amount of gray in all black pigments. Chromo- 

 lithography can be made to produce clearer and better 

 shades of the pure colors, but is distinctly objectionable 

 for the purpose of a work of this kind owing to eventual 

 oxidation of the oil or varnish with which the pigments 

 are combined in lithographic inks, causing a change of 

 hue; reds becoming more orange, blues more greenish, 

 etc., in course of time. 



While the absence (in large part) of pure chromatic 

 shades is much to be regretted, the defect js not so seri- 

 ous, from the standpoint of utility, as might appear at 

 first sight ; for while saturated or darkened pure colors 

 are not uncommon in the animal, vegetable, and mineral 

 kingdoms, more or less broken dark colors are infinitely 

 more so; and since the latter are greatly increased in 

 number by the defect mentioned the actual result is 

 rather an advantage than otherwise. 



It will doubtless be noticed that there is a conspicu- 

 ous difference in relative darkness between shades of 

 yellow and contiguous hues on the one hand and corre- 

 sponding ones of violet and adjacent hues on the other, 

 as if the percentage of black in each were very different. 

 This, however, is entirely the result of difference of 

 luminosity of the two sets of colors, that of yellow being 

 between 7000 and 8000 while that of violet is only about 

 13;* for the percentage of black in corresponding tones 

 of the vertical scales is precisely the same for each color 

 throughout the chromatic scale of this work. 



*See Rood, Modern Chromatics, pages 34, 35. 



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