Explanation of Plates. 5 



by the middle horizontal line of color-squares on Plates 

 I-XII (together with an equal number of intermediates 

 represented by blank spaces) , requiring a separate curve 

 and consequently different relative proportions of the 

 two component colors for each series of hues — that is, 

 the series from red to orange, orange to yellow, yellow 

 to green, green to blue, blue to violet, and violet to red, 

 respectively; but the progressive increments of white in 

 the scales of tints, black in those of shades, and neutral 

 gray in the several series of broken colors are exactly 

 the same in every case. The first series of Plates (I-XII) 

 shows the pure, full spectrum colors and intermediate 

 hues (middle horizontal line, nos. 1-72),* each with its 

 vertical scale of tints (upward, a-g) and shades (down- 

 ward, h-n), the increments of white for the tints being 

 9.5, 22.5, and 45 per cent., respectively, those of black 

 in the shades being 45, 70.5, and 87.5 percent. The 

 remaining Plates show these same thirty-six colors or 

 hues in exactly the same order and similarly modified 

 (vertically) by precisely the same progressive incre- 

 ments of white (upward) and black (downward), but 

 all the colors are dulled by admixture of neutral gray; 

 the first series (l'-72\ Plates XIII-XXVI) containing 32 

 per cent, of neutral gray, the second (l"-72", Plates 

 XXVII-XXXVIII) 58 per cent., the third (l'"-72"\ 

 Plates XXXIX-XUV) 77 percent., and the fourth (l""« 

 72'"', Plates XLV-Iy) 90 per cent. The last three 

 Plates (LJ-L,III) show the six spectrum colorsf (also 

 purple, the intermediate between violet and red) still 

 further dulled by admixture of 95.5 per cent, of neutral 



*The number is doubled so that every other one represents an intermediate hue 

 not shown in color. 



fOwing to the circumstance that spectrum orange does not, at least when mixed 

 with gray, fairly represent a medium hue between red and orange, being much 

 nearer the former, a hue much near to yellow (yellow-orange, No. 15) has been 

 selected. 



