192 



BIOLOGICAL EFFECTS OF RADIATION 



and shorter wave-lengths, 2536 A being the last line of any great intensity 

 emitted by the mercury arc. Referring to Table 16, we find from 



2400 



2800 



4000 



3200 3600 



WAVE LENGTH 



Fig. 30. — Upper section — transmission of filters: BF — barium flint, 3.18 mm. (thickness) 

 (50); CD— corex D, 2.3 mm. (21); CA— corex A, 2.86 mm. (21); Q— fused quartz, 4.7 mm. 

 (21). Center section — sensitivity of detectors and erythemal response curve: Q-BF, 

 balanced thermocouple with quartz and barium-flint filters; CA-BF, balanced thermo- 

 couple with corex A and barium-flint filters; CD-BF, balanced thermocouple with corex 

 D and barium-flint filters; E, erythema (24); ZnS-1, lithopone A (13) (Brickwedde); 

 ZnS-2, balanced zinc sulphide method with quartz and barium-flint filters. Lower 

 section— response to solar energy: Sun, solar energy (28) (Forsythe and Christison); S, 

 response of standard balanced thermocouple to solar energy; ZnS-2, response of balanced 

 zinc sulphide detector to solar energy; E, erythemal response to solar energy. 



Column 7 that the amount detected by this method in microwatts/ 

 square centimeter at 25 cm. from a 2.0-cm. midsection of arc shows a 



