ABSTRACT
A Full account of the growth of stellar spectroscopy would take us too far from the purpose of this little book, and it is not easy to find a suitable place to consider it as a whole. The principles of the Astrographic Conference, and of the International Solar Union, have already extended into stellar spectroscopy, which has not yet seen its jubilee. The calcium absorption is the strong feature of this class, and we have already noted its importance in the case of the sun, especially in regard to the prominences of the chromosphere. In Lockyer's 'Meteoritic Hypothesis', published in book-form in 1890, after appearing from 1887 onwards in a series of communications to the Royal Society, the evolution was traced from nebule through seven stages-gaseous, Antarian, imperfect solar, Sirian, true solar, carbon, and extinct. But between solar stars and red stars the gradation is not so regular; there are 'missing links'.
