Watson, Color Vision in Monkeys. 



15 



these conditions arc introspcctivelv similar to those made with an 

 ordinary photometer,. The images of T^ and C appear side by 

 side, with no dividing surface between. Six judgments for each 

 change in the intensity of the band were made, three ascending and 

 three descending, and the results averaged. 



The units in which the results below are given are "hefner- 

 meters." In other words, the apparatus measures the "intensity 

 of illumination" of the variable surface, Y, in terms of C, the "in- 

 tensity of illumination" of which can be calculated from the for- 

 mula : 



Cos (9 ■ 

 r* 



(($>= 45^ in all cases; r is read directly from the scale of B). ^^ 

 The following table of constants gives the wave lengths of the 

 four bands used in the present work and their "intensity of illumina- 

 tion" under the various conditions. 



Table of Constants. 



Width of Monochromatic Bands. 



Red = A 6485 — 5790. 



Yellow = A 5750 — 5600. 



Green = A 5250 — 4825. 



Blue = A 4800 — 4650. 



"The angle 6 refers to the angle at which the light from the source falls 

 upon the cardboard C. 



"These are broad spectral bands, mutually exclusive, but not "monochro- 

 matic" in the sense in which the physicists use that term. 



