THE ULTRA VIOLET COMPONENT IN ARTIFICIAL LIGHT. 



By Louis Bell. 

 Presented March 13. Received March 25, 1912. 



Purpose of the Invest igati on. — The fundamental purpose of this 

 study has been definitely to evaluate the amount of energy given by 

 various artificial illuminants in the ultra violet portion of the spectrum. 

 In particular, beside determining the general proportion of ultra 

 violet rays and their actual amount in each lamp investigated, the 

 writer has determined in absolute measure the ultra violet energy 

 delivered by each light source for unit illuminating value. Assuming 

 that each of the artificial lights studied is to be used to produce a 

 certain given illumination, the amount of ultra violet radiation in- 

 cidental to that illumination has been set down in absolute terms of 

 ergs per second per sq. c. m. This classification of illuminants, which 

 has not hitherto been made, is important in view of the possible 

 harmful effects of radiation of short wave length which have been 

 repeatedly discussed during the past few years. The amount of such 

 possibly injurious radiation given by any particular lamp is a matter 

 of small importance except as it is correlated with the illuminating 

 power of the lamp, so that one may know to what amount of possibly 

 harmful radiations he is exposed in securing a required degree of 

 illumination. 



Nature and extent of Radiations under Suspicion as harmful. — There 

 has been much discussion concerning the effects of radiations of 

 different wave lengths upon the eye. Without going extensively 

 into an examination of the literature, which is very scattered and 

 extensive, or of the physiological facts, some of which the writer now 

 has under careful investigation and which will be reported later, it is 

 sufficient here to say that the investigators of this matter may be 

 divided into somewhat divergent schools. All agree that the extreme 

 ultra \iolet rays, those of wave length less than 300 /jl/jl, which are 

 absorbed by the cornea and so do not penetrate to the inner parts 

 of the eye, produce when in sufficient intensity more or less serious 

 damage to the corneal ephithelium, resulting in acute irritation, 

 always accompanied by conjunctivitis, and sometimes by cloudiness 

 of the cornea and other symptoms which go to make up the complex 



