RELATIVE PHYSIOLOGICAL VALUE OF SPECTRAL LIGHTS 515 



department of the College and we have the unrestricted use of it only 

 during the vacations, thus retarding our progress. Furtherrr.ore extra 

 work which we have both agreed to undertake during the coming college 

 term will leave us little time for research. 



Since it is highly improbable, therefore, that we can publish anything 

 in the near future concerning results obtained with our apparatus, we 

 are desirous of publishing a preliminary description of it so as to afford 

 those who are interested in similar studies the benefit of our experience 

 in the construction of an apparatus fulfilling what we consider the 

 necessary physical conditions for the study of the relative stimulating 

 value of spectral lights. 



SUMMARY 



The reasons are stated why the study of the relative stimulating value 

 of different colored lights should be carried out with a high degree of 

 exactness for all, even the lowest forms. This involves the use of pure 

 "monochromatic" lights, directly m.easurable in terms of energy and 

 preferably made equal in radiant energy content, thus doing away with 

 the necessity of making corrections for this. 



An apparatus is described which delivers lights of equal radiant en- 

 ergy content. Each light is a band 30 wave-lengths wide. The lights 

 now obtained are twenty-three in nuro.ber and extend, by steps of 10 

 wave-lengths, from 420 /^m to 670 ixix. The apparatus used for equat- 

 ing the radiant energy content in the different lights is also described. 



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