THE LUMINOSITY OF THE SPECTRUM 



47 



phenomenon (p. 57). Maximum luminosity is at about (JlO/x/x with 

 these intensities. Krarup^ has calculated the curves from Konig's 

 results in terms of the energy values of the spectrum, making allowance 

 for absorption by the macular pigment, so that the results are inde- 

 pendent of the particular source of light. 



Abney's luminosity curves for the spectrum of the arc light with 

 inclined carbons are shown in Fig. 11. They were also obtained by 

 the equality of brightness method. 



The following are the macular luminosities for the chief Fraunhofer 

 lines, the source of light being the crater of the positive pole of the 

 electric arc, with sloping carbons : 



The difference between the luminosity curve by the equality of 

 brightness method and the flicker luminosity curve is shown in Fig. 12. 



/oo 



90 

 80 

 70 



60 

 50 

 -fO 

 30 

 20 

 /O 



SS/^ 26 30 55 'fO -fS SO S5 60 65 



Fig. 12. Normal trichromat's photopic luminosity curves with the equality of brightness 

 and the flicker methods. Abscissae, arbitrarj^ scale of the prismatic spectrum of 

 the arc light ; ordmates, arbitrary scale, the maximum luminosity by the equality 

 of brightness method being 100. (Abney.) (Cf. Fig. 38.) 



^ Loc. cit. p. 46. 



