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



tube, C {after Ives and Cohlentz). 



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

 pyralis (3); and the firefly Photuris pennsylvanica (4) {after Cohlentz). 



