Composition of Tones. 



23 



TABI.E 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) 



(g) 

 v f 

 (e) 



d 

 (c) 



b 



(a) 



(Full Color) 



(h) 



i 



(j) 

 k 



(1) 



m 



(n) 



(Black) 



100 



70 

 45 

 32 



22.5 

 15 



9.5 



5 







30 

 55 



68 

 77.5 



85 

 90.5 



95 

 100 



64 

 55 



41 

 29.5 



20 



12.5 

 6 





1 



1 













26 

 45 



59 

 70.5 



80 



87.5 

 94 

 100 





















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 



