8 Mayer — Phenomena of Simultaneous Contrast-Color, 



The hue of the rose-colored rings as seen through the tube 

 is much more intense than the hue of the ring viewed on the 

 emerald ground with the unassisted eye. Experiments made 

 with the aid of an achromatized calc spar prism, and by match- 

 ing on a rotating disk the colors of the gray ring on an emerald 

 green ground showed that the intensity of the contrast-color, 

 as seen with the reflecting tube is nearly double of what it is 

 when viewed by the eye alone. The color of the ring when 

 viewed by the unassisted eye was matched on the rotator by a 

 disk having 30 parts of Chinese vermillion + 7 of "Hoffman's 

 violet R P. R" + 34 parts of ivory- black + 29 of white 

 Bristol board. As seen through the reflecting tube the match 

 appeared to be given by 57 of Chinese vermilion + 15 of 

 " Hoffman's violet E. R R" + 28 of white Bristol board. 



Another tube, 4 # 5 cms in diameter and 18 cms long gave excel- 

 lent results, with two reflected rings, and on nearer vision, with 

 four reflected rings. A tube, suitable for these experiments, 

 is selected by closing one of its ends by a disk of cardboard 

 having a pin hole at its center. When the end with the pin 

 hole faces the sky and we look through the other end we see 

 bright rings caused by the reflection of the light of the pin 

 hole from the surface of the tube. If these rings are circular 

 and concentric the tube is of circular section and its axis is a 

 right line. 



The value of this mode of observation is shown by the fol- 

 lowing experiments. Place the ring of gray paper, or, a circle 

 of gray paper, about l^ cms in diameter, on a surface painted 

 with cobalt blue, not too saturated. The gray ring, or, circle, 

 appears of an orange tint. Place a similar gray ring, or, circle, 

 on a surface lightly washed with emerald green, it appears 

 pinkish. The difference between the hues of the ring when 

 viewed on the cobalt blue and on the emerald green though 

 decided is not strongly marked ; but if viewed through the 

 reflecting tube the ring on the cobalt blue appears of a rather 

 intense orange and the ring on the emerald green appears of a 

 rose color. When so viewed the difference in these hues is 

 strongly marked. 



Pieces of card-board, painted with the following colors, 

 were arranged in pairs. Orange yellow on the less refrangible 

 side of D, and orange yellow on the more refrangible side of 

 D. Greenish yellow and yellowish green, both made with 

 gamboge and Prussian blue. Purple of violet end of spec- 

 trum with added red, made with Hoffman's violet R P. P., and 

 violet between G and H, Young and Miiller's fundamental 

 color. Place a pair of the colors, as given above, side by side 

 and on each put a gray ring, with a reflecting tube over each 



