1912.] 



Colour Adaptation. 



113 



instrument must have been previously in a state of daylight adaptation. 

 It will now be found that 13 blue illuminated by electric light almost 

 exactly matches 12 brown illuminated by daylight. 



The following shows the changes in the appearance of the colours of the 

 previously mentioned cards when two exactly similar cards are illuminated 



in the photometer on the one side by daylight and on the other by Osram 

 electric light. The eye used was daylight-adapted : — 



Illuminated by day- 

 light. 



Illuminated by electric- 

 light" 



(Osram incandescent). 



Illuminated by day- 

 light. 



Illuminated by electric- 

 light 



(Osram incandescent). 



1. Greenish-yellow 



2. Brown 



3. Slate 



4. Blue 



5. Green 



6. Green 



7. Brown 



8. Green 



9. Pure green 



10. Greenish-yellow 



Orange 



Orange 



Brown 



Grey 



Yellow 



G-reenish-yellow 

 Orange 

 Yellow-green 

 Dark yellow 

 Orange 



11. Greenish -yellow 



12. Chocolate 



13. Blue 



14. Brown 



15. Slate 



1 6. Eose red 



17. Eose 



18. Brown 



19. Blue-grey 



20. Brown 



Orange 

 Orange 



Purplish-black 



Orange 



Brown 



Scarlet 



Orange 



Yellowish-orange 



Yellow-brown 



Orange 



It will be seen that colour adaptation greatly assists the correct dis- 

 crimination of colours. 



The same cards were now examined in exactly the same physical condi- 

 tions, that is to say, two exactly similar cards were placed in the photo- 

 meter, and one side was illuminated by daylight and the other by electric 

 light. The eye used for viewing the cards was adapted to electric light 

 by viewing white paper illuminated by electric light (Osram incandescent) 

 for from 5 to 10 seconds. The cards used were the same as before. The 



following results were obtained : — 



Illuminated by day- 

 light. 



Illuminated by electric 

 light 



(Osram incandescent). 



Illuminated by day- 

 light. " 



Illuminated by electric 

 light 



(Osram incandescent). 



1. Green 



2. Buff 



3. Blue 



4. Bright blue 



5. Green 



6. Blue-green 



7. Grey 



8. Blue 



9. Green 



10. Yellow-green 



Orange-yellow 



Orange 



Grey 



Blue-grey 

 Yellow- green 

 Yellow-green 

 Pale orange 

 Black 



Yellow-green 

 Orange-yellow 



11. Greenish-yellow 



12. Purple-brown 



13. Bright blue 



14. Grey 



15. Slate 



16. Eose 



17. Purple 



18. Purple- brown 



19. Blue-black 



20. G-rey 



Orange-yellow 



Orange 



Dark blue 



Brown 



Grey 



Red 



Orange 



Orange 



Black 



Light brown 



When a match had been made to the daylight-adapted eye of chocolate 

 brown 12 illuminated by daylight, and blue 13 illuminated by electric light, 



