AbstractIn the course of the 1961 Perseid shower, ten faint spectra were obtained with one spectrograph. The spectra can be classified into four groups, which form a continuous sequence. The forbidden green line of neutral oxygen at 5577A is visible in the two brightest spectral classes, but appears weaker in the spectrum showing the H and K lines of ionized calcium than it does in those that do not. The green line appears to be relatively stronger in the spectra of faint meteors. An attempt is made to explain some aspects of green line behaviour with the aid of the Whipple comet model.