NO. 2 EFFECT OF ULTRAVIOLET ON ALGAE MEIER 3 



and double monochromator is similar to the one described by Brackett 

 and McAlister (1932). 



INTENSITY DATA 



The intensity data for plates 39 to 57 are recorded in table i. 

 Intensities were measured with a thermocouple. The values to be 

 given below represent the average intensities over the areas affecting 

 the algae. A special experiment was planned to test the joint propor- 

 tionality of the intensity of irradiation and the time of irradiation to 



Table i. — Intensify Data 



the lethal effect. Accordingly, a smaller diaphragm was placed over the 

 lens of the spectrograph so that fiv^e plates, plates 58-63, could be ir- 

 radiated at I the original intensity, /. e., the intensity used for irradia- 

 tion of all the previous plates. By the adjustment of a 20-cm focal 

 length lens in place of a 30-cm lens at the camera end of the spectro- 

 graph, a shorter, more intense spectrum was obtained, giving lines 

 three times the intensity of the original sjxictrum. This verv intense 

 spectrum was used to irradiate plates 64-67. The intensity data for 

 the ^ and 3-fold intensities are recorded in table 2, together with 

 the original intensities of December 14. 



