Fig. 7.—Spectra of carbon glow lamp, A, firefly (Photinus pyralis); B, and helium vacuum tube, C (after Ives and Coblentz).
Fig. 8.—Spectra of helium vacuum tube (1); carbon glow lamp (2); the firefly, Photinus pyralis (3); and the firefly Photuris pennsylvanica (4) (after Coblentz).