Bright and pale yellow paper. 



Experiment 34 

 44 



75 

 79 



Yellow glass. 

 Experiment 37 13 



A yellow background tends 

 most strongly of all to pro- 

 duce the brightest pni^as, not 

 a single exception occurring. 

 In this case the paper retiects 

 the same rays, with the addition 

 of a broad strip of green, and 

 the green-yellow rays are less 

 absorbed. Comparison with the 

 green backgrounds proves that 

 it is the additional yellow rays 

 rather than the green, which 

 are effective. Light transmitted 

 through yellow glass, and re- 

 flected from light wood, tends 

 (in this case) in the same direc- 

 tion as the yellow background. 



Faded yellowish green tissue-paper. 



Experiments 3 & 4 

 15 

 39 



2 =2 

 1 =1 

 1 =1 



4 



Bright green paper. 

 Experiment 80 I |l|l|l| =3 



Dark green paper. 

 Experiment 81 1 2 \ ~^ 



Green glass. 

 Experiment 16 



12 =12 



Green gelatine. 

 Experiment 38 1 I 1 I =2 



Although used as a complete 

 covering, the tissue-paper acted 

 as a background as well as a 

 screen. Its thickness was very 

 irregular, and there were many 

 minute holes, so that a large 

 amount of white light passed 

 through it, and the conditions 

 resembled those of a coloured 

 background in light rather than 

 those of a screen i:)laced in front 

 of a white surface. It reflected 

 chiefly the green rays and most 

 of the red, orange, and yellow, 

 while the blue was much ab- 

 sorbed. It produced bright 

 green pupa3 without exception. 

 On the other hand, the bright 

 green paj)er, absorbing the red, 

 orange, and yellow strongly, and 

 reflecting much of the blue as 

 well as green, produced far 

 darker pupas ; while the dark 

 green, absorbing much of every 

 part except the green (and some 

 of this), tended to form distinct 

 dark pupfe. The green glass 

 placed in front of white paper, 

 and the green gelatine in front 

 of light wood, produced effects 

 entirely opposite to the green 

 backgrounds, although the 

 transmitted light was by no 

 means rich in yellow and 

 orange. 



