Measurements in the Spectrum of the Shell Star HD 218393.

The proffles and displacements of various hydrogen lines present complex and changing patterns. Various members of the Balmer series frequently yield quite different displacements on the same plate. The term "Balmer progression" is suggested to indicate the trend of measured radial velocity from suc- cessive lines of the series. Lines of ionized metals vary in intensity; their displacements usually correspond to those of the hydrogen lines toward the limit of the series