Plate II 



PHOTOMETRIC CURVES?. 

 FOR EQUAL TOTAL AMOUNTS OF LIGHT. 

 A — S)in-li{lfif. 



B—Firt'-Un liijiit. 



Abscissae.— Wave Lengths. 

 Ordinates.— Luminous Intensities. 



A. Sun-light Spectrmni. 



B. Fire-fly Spectrum. 



