56 



THE NATUKE OF ANIMAL LIGHT 



lights and is obtained from a knowledge of the radiated 

 energy and the visual sensibility. Reduced luminous efl&- 

 cieney = light {radiated energy X visual sensibility) or 

 luminosity -=- total radiated energy. 



0.4S 0.52 



Author 



— — Coblentz & Emerson 



0.60 



0.64 



0.68 



-Reeves 



-Ivea 



Nutting 



Pig. 12. — Visibility curves of various investigators obtained by different methods {afitr 

 Hyde, Forsythe and Cady). 



The spectral energy curve for the firefly has been 

 ■worked out by Ives and Coblentz (1910), using a pho- 

 tographic method in which the intensities of different 

 wave-lengths of the firefly {Photinus pyralis) light is com- 



