stars, the apparent splitting into three groups of the spectral sequence for temperatures below 4000°, the problem of the c-stars, the Cepheid variables with their variable spectra, and the variables of long period.
It is not possible, in a work like the present, to touch upon many of these subjects, and the writer has selected for brief discussion three upon which she can contribute new material: the problem of the
stars, the classification of the
stars, and the interpretation of the spectra of the stars that display the c-characteristic.
THE STARS OF CLASS
The statistically negligible class containing the