ent known intensities of light were passed through the monochromatic gelatin 

 filters. 'Colors reversed' means that the color which in the first part of an experi- 

 ment had indicated the presence of food was changed to mean paper, and that food 

 was now given on the color with which paper had formerly been associated. The 

 letters indicate the colors; blue is represented by B, green by G, red by R, violet by 

 V and yelloiv by Y. 'Gray plates' means that 'fogged' photographic plates were used 

 and that the source of the light shining through them was an incandescent lamp. 

 'Square and dots' means that, instead of monochromatic gelatin filters, glass plates 

 with these designs on them were used with the light from an incandescent lamp 

 passed through them. The appearance of the square tvas accompanied by food and 

 the dots by paper. 



No. 25 <! 



No. 27 



No. 40 



No. 



No. 60 



TYPE OF EXPERIMENT 



R and G papers 



R and G lights from flash- 

 lights 



Lights dim 



Batteries renewed 



B and R papers 



V and B papers 



B and R lights from flash- 

 lights 



Lights dim 



Batteries renewed 



R and G lights 



Intensity varied 



Square and dots 



G and R lights from flash- 

 light 



Lights dim 



Batteries renewed 



Colors reversed < 



G and R lights 



Intensity varied 



G and R lights 



Intensity varied 



G and R lights 



Intensity varied 



Gray plates 



G and Y lights 



Gray plates 



ss 



11.11 



42 8'. 



48.14 



6.66 



25.00 



20.28 



53.49 

 58.64 

 0.00 

 34.78 

 14.58 

 90.2 



12.50 

 59.46 



0.00 

 51.62 



0.00 

 36.00 

 17.02 



16.66 

 0.00 

 12.9 

 11.11 

 82.15 



23.07 

 93.37 



461 



