IN a paper by Johnson and myself (Proc. Roy. Soc. A, vol. 106, p. 200) on the effect of argon on certain spectra, attention was directed to structural modifications induced in the CH band, 4315, and in the CN bands, these being similar to changes observed by Strutt and Fowler (Proc. Roy. Soc. A, vol. 86, p. 116), when these spectra were stimulated in the afterglow of nitrogen. In a recent paper by Johnson (Phil. Mag. vi., vol. 48, p. 1069) further evidence has been adduced for the similarity of the electrical conditions obtained in the afterglow to those existing when mild uncondensed discharges are passed through high-pressure argon. In particular, an energy displacement in the first positive band spectrum, as developed in a tube containing a little nitrogen in the presence of high-pressure argon, was regarded as the analogue of the selection of three of the more refrangible heads in the several groups constituting the visible spectrum of the afterglow. The energy displacement was related quantitatively to the percentage of nitrogen in the nitrogen-argon mixture. If the analogy can be sustained, it should follow that the intensity maximum in the several groups of the afterglow spectrum will be displaced a little towards the violet end as the afterglow is dying away (that is, as the percentage of activated molecules diminishes).