Plate III 



Pour Curves of Equal Areas, showing- one unit of heat displayed 

 successively in heat spectrum of Gas, Electric Arc, Sun and 

 Fire-Fly. 



Abscissae. -Wave Lengths. 

 Ordinates. — Energy as Heat. 



0{4- 0.6 



500— 

 400— 

 300- 

 200- 

 lOO- 

 0- 



800- 

 700- 

 600- 

 500— 

 400- 

 300—] 

 200- ; 

 100— 

 0- 



ENERGY CURVE. 



Electric Arc SiDcctrum. 



MAXIMUM AT 1*^16. 



Fig. 2. 



400- 

 300— 

 200- 

 100- 

 0— 



ENERGY CURVE. 



Solar Spectrum. 



MAXIMUM AT 'o'^62 



Fig. 3. 



LIMITS 



OF 



VISIBLE 



SPECT/iUM. 



ENERGY CURVE. 

 Fire-Fly Spectrum. 



MAXIMUM AT 0*^57. 



Fig. 4. 



il 



0.6 



