4 Color Standards and Nomenclature. 



LIU.) These colored disks are slit on one side from 

 center to circumference, and therefore by interlocking 

 two or more they may be adjusted so that either occupies 

 any desired percentage of the whole area, which may be 

 very precisely determined by a scale of 100 segments 

 shown on the outer edge of a larger disk on which the 

 colored disks are superimposed. When connected with 

 the color- wheel and adjusted as may be desired, and then 

 rapidly revolved, the two or more distinct colors resolve 

 themselves into a single uniform composite color, whose 

 elements are shown, in their relative proportion, by the 

 scale surrounding the disks.* 



The scales (both horizontal and vertical) of the 

 present work are all prepared directly from definite 

 color-wheel formulae, based on carefully calculated 

 curves; the thirty-six pure spectrum hues, represented 



*See the colored figure on the frontispiece of this work, which clearly illustrates this 

 method of color measurement. Larger disks of spectrum red, green, and violet are 

 interlocked and adjusted so that they present, respectively, 32, 42, and 26 per cent. 

 of the circumference ; superimposed on these is a single smaller disk of neutral gray, 

 and on this two still smaller disks of black and white, the former occupying 79, the 

 latter 21, per cent, of the area. The result of this combination of colors, when the 

 disks are rapidly revolved, is that the entire surface becomes a uniform neutral gray 

 precisely like the middle disk, which blends so completely with the color inside and 

 outside its limits that no trace of division can be detected. Hence, neutral gray 

 equals a combination of red 32, green 42, and violet 26 per cent., and also equals a 

 combination of black 79 and white 21 per cent. As further illustrating the point, it 

 may be mentioned that not only does the above-mentioned combination of the three 

 primary colors equal neutral gray but so also does the combination of any color 

 ("secondary" or "tertiary" as well as primary) with its complementary, though the 

 darkness or lightness of the gray varies somewhat, as the following table shows : 



Spectrum Color. 



Complementary Color. 



Equivalent 

 Gray. 



Name. 



Per 



Cent. 



Per 

 Cent. 



Composition. 



Black. 



White. 



Red 



44 



28.5 



33 



51 



64 



62.5 



56 



71.5 



67 



49 



36 

 37.5 



Blue 41 + Green 59. 72.5 

 Blue 51.5 + Green 48.5. j| 69 

 Blue 60.5 + Violet 39.5. jj 64 

 Red 57.5 + Violet 42.5. 73 

 Yellow 82 + Orange 18. 62 

 Yellow 69 a- Green 31 1 61.5 



27.5 





31 



Yellow 



36 





27 



Blue 



37 



Violet 



38.5 











