2 Mayer — Phenomena of Simultaneous Contrast- Color, 



Place the screen, thus formed, in front of a petroleum lamp 

 and exclude the daylight from the side thus illuminated. The 

 other side of the screen is illuminated by the light of the sky 



admitted through a distant window. 

 The cardboard ring is thus illumi- 

 nated on one side only by the lamp ; 

 on the other side, only by the day- 

 light. The translucent paper trans- 

 mits the lamplight to the side facing 

 the window, while it transmits the 

 daylight to the side facing the lamp. 

 On the side of the screen facing the 

 window the cardboard ring appears 

 cyan-blue while on the side facing the 

 lamp the ring appears orange yellow. 

 Hues of the sides of the ring. — An 

 idea of the hues and intensities of 

 these colors, which cause astonishment 

 even in those who are experimenters 

 in chromatics, will be given by the 

 description of the following experi- 

 ments. 



By means of a Bunsen-photometer 

 disk I adjusted the distance of the 

 lamp from the screen so that I ob- 

 tained, as nearly as I could judge, 

 equal illumination of the sides of the 

 screen. I then found that the blue was matched in a rotator 

 by a disk having a sector of 60 parts of the circumference of 

 Prussian blue, with a sector of 10 parts of emerald-green and 

 a sector of 30 parts of white cardboard. The blue was that 

 of one of the many colored disks given me by Professor O. IS". 

 Pood and was marked, "Blue between cyan-blue and the 

 ultramarine of the physicist, but nearer the latter. Near F 

 and on its more refrangible side. Made with Prussian blue." 

 The blue on this disk appeared as saturated in hue as could 

 be made by the pigment. 



The match of the color of the side of the ring facing the 

 lamp, L in fig. 3, was obtained by placing a silvered mirror, 

 M, so that the reflection of this side of the ring, S, was seen 

 close to the rotator, P. 



The color of the cardboard ring facing the lamp was 

 matched by the rotation of a disk formed of 50 parts of chrome 



Fig.l 



of red lead (red orange) and 20 parts of 



Such appears to be the hue of the light of 



in this manner, with the 



yellow, 30 parts 



white cardboard. 



a petroleum flame when compared. 



light of the sun. 



