8B2 



in agreement with that found by Ciamician and Silber for the red 

 fluorescein filter we found that the filters I and II which only 

 transmit red (690 — 598 /ii/i) or red and green (^500 ,uf/) absorbed 

 all actinic rajs. 



Also V, which besides red ivajs of about 700 (iii still transmitted 

 blue and violet ^ 433 uft, completely prevented the rednction in the 

 inner tube. On the other hand an important reduction took place with 

 the filters III, IV, and VI which ti-ansmifted i-avs to the extreme, visible 

 violet ± 400/<;7. 



The series of experiments were conducted in this way that a set 

 of four jacketed tubes with photo-filters were exposed to sun-light 

 for some days in front of the white screen: the results are contained 

 in the subjoined table. 



TABLE IX. 



