54 



COLOUR VISION 



'00 



90 



30 



70 



60 



50 



40 



30 



20 



- 10 



6 8 



10 \Z 14 16 18 ZQ Zt 24 26 2& 50 52 JS4 56 58 40 42 44 46 48 50 52 54 56 58 60 62 64 66 

 22-8 34 39 8 50 6 591597613 



Fig. 14. Normal trichromat's photopic and scotopic luminosity curves. (One amy] 

 acetate or Hefner unit is equal to 0-9 international candle power. ) Abscissae, arbitrary 

 scale of the prismatic spectrum of the arc light ; ordinates, arbitrary scale, the maxi- 

 mum of luminosity being in each case 100. (Abney and Festing.) 



01 2345678 9 10 1112 13 14 15 



oioi olOioicnoicnoioicn 



Ol 05 Ol O) O) 

 ^ Oi CO -* O 

 0-» -t».(DCOCD^ 01CnO>-«l CONOCnCD K3 



CD CD CO -* 



W-* 4kO*>.IO COOJ J^-J fO 



23 



25 



27 



4^ 

 CO 



ID 



Fig. 15. Scotopic luminosity curves. 



trichromat). — Nagel's curve (deuteranope) 



Schaternikoff's curve (normal 

 X X X X X and o o o o o. 



other observations by Nagel. Abscissae, wave-lengths of the prismatic spectrum 

 of gas light ; ordinates, arbitrary scale. (Schaternikoff.) 



