20 Mayer — Phenomena of Simultaneous Contrast- Color, 



The hue of the light of " a white incandescent Welsbach 

 lamp 71 compared with daylight. — When the screen, fig. 1, is 

 illuminated on one side by the Welsbach lamp and on the other 

 by daylight, the side of the ring of the screen facing the 

 daylight appears a feeble blue decidedly tinged with violet. 

 The side of the ring facing the Welsbach lamp is colored 

 greenish orange. This greenish orange was matched in hue, 

 but not in luminosity, by a rotating disk having 41*5 parts of 

 red lead, 41*5 of chrome yellow and 17 of emerald green, viewed 

 illuminated by daylight. This appears to be the hue of the 

 Welsbach light when compared with daylight. 



Experiments in which are compared the hues of the light of 

 an incandescent Welsbach lamp and of candle light. — When 

 "a white-light incandescent Welsbach lamp " is placed on one 

 side of the large screen, fig. 1, and a candle, or petroleum 

 flame, on the other side, the cardboard ring of the screen fac- 

 ing the Welsbach light appears of a light bluish green ; the 

 side of the ring facing the candle, or petroleum flame, appears 

 of a light carmine. 



Matching these hues on the rotator with split disks gave the 

 following results when the two sides of the screen were equally 

 illuminated. The hue of the ring on the side facing the 

 Welsbach lamp was matched by 8 parts of emerald green, 10 

 of cobalt blue, 25 of ivory black and 57 parts of white Bristol 

 board, as seen illuminated by the Welsbach lamp. The hue 

 on the side of the ring facing the candle or petroleum flame 

 was matched by 12 of carmine, 17 of ivory black and 71 of 

 white cardboard, as seen illuminated by the petroleum flame. 



Experiments with the rotating -photometer disk placed be- 

 tween the Welsbach lamp and the petroleum flame. — On rotat- 

 ing the photometer disk, without any central disks, between 

 these lights, the same hues as those already described were 

 seen on its sides, only these hues were much less saturated. 



The white disks placed on the sides of the rotating pho- 

 tometer made the hues less saturated. 



With a white disk on the petroleum flame side and a black 

 disk on the Welsbach lamp side the difference between the 

 hues of the sides of the photometer were more pronounced. 



With a disk of cobalt blue, emerald green and white on the 

 Welsbach-light side and a white disk on the petroleum flame 

 side, the side of photometer facing the Welsbach lamp ap- 

 peared white and the side facing the petroleum flame was less 

 carmine ; the differences in hue being less than in any of the 

 previous experiments. 



By trial I found that when a disk of 33 parts of emerald 

 green, 42 of cobalt blue and 25 of white was placed on the 

 Welsbach lamp side of the photometer disk, with a ring of the 



