The study of optical spectra of positive rays is continued with the type of tube and Merton wedge described previously. The direction of observation is here longitudinal, in order to isolate the Doppler effect in the "moving" spectrum: accordingly a six-prism spectrograph is substituted for the échelon used with a narrower line in Part I. The results are added to those of Stark, Paschen, Wilsar and Krefft on the same spectrum, and the uncertainties in identifying atomic and molecular carriers are analysed. The distribution of velocity among the particles contributing to the "moving" spectrum is compared with the distribution of velocity in positive rays measured by the electromagnetic method and with some investigations of Retschinsky and Döpel. The appearance of the many-lined spectrum of hydrogen in the positive rays, and the ratio of intensity of the "moving" and "resting" spectra are also considered. The inverse square law of probability of electron capture, and some consequences of the work of Wien and Rüchardt, are the most likely controlling factors in the several phenomena.