Fig. 7. — Spectra of carbon glow lamp, A, firefly (Pkotinus pyralis); B, and helium vacuum 

 tube, C {after Ives and Coblentz). 



g!§^ 



Fig. 8.— Spectra of helium vacuum tube (1); carbon glow lamp (2); the firefly, Photinus 

 pyralis (3); and the firefly Photuris pmnsylmnica (4) (.after Coblentz). 



