Composition of Tones. 
Jo 
tabee showing percentage of white and black, 
respectively, in each tone of the 
TONE OR LUMINOSITY SCALES. 
All. of the vertical scales in the original Plates of 
this work (the scale of carbon grays alone excepted) 
contain the following percentages by color-wheel meas¬ 
urement : 
Tone. 
Percentages. 
White. 
Color. 
Black. 
(White) 
100 
(g) 
70 
30 
f 
45 
55 
(e) 
32 
68 
d 
22.5 
77.5 
(c) 
15 
85 
b 
9.5 
90.5 
(a) 
5 
95 
(Full Color) 
100 
(h) 
64 
26 
i 
55 
45 
(j) 
' 
41 
59 
k 
29.5 
70.5 
(1) 
20 
80 
m 
12.5 
87.5 
(n) 
6 
94 
(Black) 
100 
1 
One of the most serious difficulties encountered in the 
preparation of the Plates of this work was the apparent 
impracticability of reproducing satisfactory shades of 
pure colors. This originated in the fact that there seems 
to be no substance (pigment, dye, or fabric) which repre¬ 
sents a true black, all reflecting more or less of white 
light, and consequently producing shades which are dull 
