730 ANNUAL KEPOKT SMITHSONIAN INSTITUTION, 1913. 



Simultaneous contrast is illustrated by regarding a strip of gray 

 against a colored field when the gray becomes tinted with the comple- 

 mentary hue. There are two simple methods for performing this 

 experiment, one is to spin a colored disk, midway between the center 

 and circumference of which is a circle, composed partly of black and 

 partly of white ; this synthesizes to a gray which becomes tinted with 

 the complementary hue of the colored field. The other Avay is to lay 

 a narrow strip of gra}'^ paper (cut as a zigzag) on a colored sheet and 

 then to cover the whole with thin tissue paper ; the gray will assume 

 the complementary hue. No experiments in color vision are more 

 striking than these, nor are there any that have more direct appli- 

 cation in the use of colors in picture painting; thus, a gray wall 

 viewed against a sunlit background of green is no gray, but like the 

 piece of paper in our experiment it becomes tinted of a purplish hue. 

 Similarly, a shadow cast on yellow sand is blue, and one thrown on 

 the skin when this is otherwise in strong light often acquires a strik- 

 ing quality of green. 



The phenomenon of successive contrast is elicited by steadily regard- 

 ing a patch of a certain color for some time and then either closing 

 the eyes, or better still, directing the gaze to a neutral surface, such 

 as a gray untinted wall. A vivid color impression of the same shape 

 as that of the colored patch previously looked at will be seen in both 

 cases, but exhibiting a hue which is complementary to that of the 

 patch. 



In the experunents above described the complementary color is 

 demonstrated by the use of a gray sm-face. It is evident, however, 

 that, if we cause it to be projected against a background which itself 

 possesses a certain hue, the two hues (the complementary and that 

 of the regarded surface) will become blended and will have the same 

 effect as if thej had been spun on a Maxwell's disk. For example, 

 suppose we regard for some time a blue surface and then direct the 

 gaze to one of red, the impression will be that of orange, because the 

 complementary of blue, being yellow, fuses with red and produces 

 orange. 



Having determined the complementaries b}' means of these contrast 

 methods we may confirm our results by color synthesis ; thus suppos- 

 ing we have determined by the contrast methods that the comple- 

 mentary for a certain yellow is a certain blue, we may proceed to 

 ascertain whether this is strictly the case by preparing disks composed 

 of these two hues and rotating them on Maxwell's machine. If the 

 hues are complementary the greatest possible degree of whiteness 

 will be produced. 



Successive contrast finds only a limited application in art, although 

 it is of course conceivable that the intensive fixation of one colored 

 area in a painting or a design might, by successive contrast, greatly 



