NO. 17 



ULTRA-VIOLET INTENSITIES- — McALISTER 



II 



Table 3 gives the intensities of radiation in the different spectral 

 regions for a distance of i m from the arc. They are expressed in 



Fig. 3. — Microphotometer curves of spectrograms of the 2,536 A. region for 

 the " high " and " low intensity " arcs. 



microwatts per cm \ Column i shows the intensity of the therapeutic 

 (4) radiation .2^ to .35/^, column 2 the near ultra-violet, visible, and 



Table 3. Filter measurements 



High Intensity 



, ,. , fmcw cm 



20 mm of vertical arc. . . > 



\ per cent 



Total vertical arc... 



Total horizontal arc. 



Low Intensity 

 20 mm of vertical arc. 



Total vertical arc... 



Jmcw cm' 

 l^per cent 



fmcw cm" 

 tper cent 



Jmcw cm" 

 i per cent 



fmcw cm" 

 \per cent 



12 3 4 5 



•2--3Si<t .35-I.4A i.4-i9,tt >I9A Total 



84 167 245 68 564 



14.8 29.7 43.4 12. 1 100 



600 1,130 2,710 350 4,790 



I2.S 23.6 56.6 7.2, 100 



615 995 2,700 370 4,680 



13.2 21.2 57.7 7.9 100 



2.8 77 77-5 8.0 96 



3.0 8.0 81.7 8.3 100 



19.8 59.6 704.8 124 908 



2.3 6.6 77.6 13.5 100 



near infra-red .35^1 to 1.4/x, column 3 the infra-red from i.4ju, to 19/^, 

 column 4 the deep infra-red beyond 19/j,, and column 5 the total 



