RELATIVE PHYSIOLOGICAL VALUE OF SPECTRAL LIGHTS 



511 



where the region of maximum stimulating efficiency was, to work 

 with a smaller number of wave-lengths. But it is difficult, under our 

 conditions, to work with bands of light less than 30 wave-lengths wide. 

 We decided therefore to increase the number of lights, keeping each 30 

 wave-lengths wide, but, beginning with a band of light extending from 

 420 MM to 450 MM) to advance through the spectrum by 10 wave- 

 length steps. The twenty-three lights thus obtained are listed in 

 table 2. 



TABLE 2 



A summary of all the conditions necessartj for obtaining twenty-three lights, each 

 30 wave-lengths uide and equal in radiant energy content 



* With reflector. 



The lamp is enclosed in an asbestos lined, blackened box (see fig. 1), 

 through an aperture in the front of which the light emerges to enter the 

 slit *S, kept at constant width, of the collimator. The back of the 



