Am. Jour, Sci., Vol. XL, 1890. 



Plate IV. 



PHOTOMETRIC CURVES. 

 FOR EQUAL TOTAL AMOUNTS OF LIGHT. 



A — Sun-light. 

 B— Fire-fly light. 



Abscissae.— Wave Lengths. 

 Ordinates.— Luminous Intensities. 



A. Sunlight Spectrum. 



JB. Fire-fly Spectrum. 



