The maxima of absorption lines in stellar spectra (second paper)

§ I. In a previous paper† we have applied the theory of hightemperature ionisation, first developed by Saha, to the positions of maximum intensity of absorption lines in the stellar sequence of spectra. During the past year the series relationship of lines belonging to treblyionised silicon and to ionised carbon, which are important in the spectra of the hotter stars, have been discovered by A. Fowler. ‡ It is the object of the present paper to use A. Fowler’s results to calculate by the method of maxima the temperatures and pressures in the reversing layers of the hotter stars. We can supplement these results by provisional estimates for certain other spectra. We deal also with a number of other points which arise in applications of the theory. § 2. Resume of the Method.—We use the terms “ principal series ” or “ principal lines” to denoto series or lines which are absorbed in transitions from the normal state of a neutral, singly-ionised, or multiplyionised atom to an excited state, or state of higher energy. We use the