INOEGANIC EVOLUTION 27 



heavens are most numerous in the parts remote from the 

 Milky Way. 



The stars are of various colours. Some shine with a white or 

 bluish- white light, like Sirius and Vega ; some are yellowish, like 

 Arcturus and our Sun ; some are reddish, like Antares ; and 

 some few are of a deep red colour. By means of the spectroscope 

 we have been enabled to analyze the light of the stars, and in 

 the main we find the elements which compose them to be 

 similar to those which occur in our earth. Yet each star- 

 spectrum presents its own peculiarities, and no two spectra are 

 exactly alike. Stellar spectra may be divided into several main 

 types, some of which I will mention, first premising that there 

 are all kinds of intermediate forms, giving us indeed an 

 unbroken series. There are gaseous or bright-line stars, which 

 have spectra showing a band of continuous light crossed, not 

 only by dark, but by bright lines mostly of hydrogen and helium. 

 Then there ai-e the so-called helium stars, which have a bright 

 continuous spectrum crossed by fine dark lines of helium 

 and hydrogen. These two types are only found in the Milky 

 Way. Then there are the Sirian stars, the most noticeable 

 thing about their spectra being the lines of hydrogen, which in 

 some of them are very thick ; their spectra are also crossed by 

 fine lines due to metallic vapours. These are most numerous in 

 the Milky Way. All these three varieties are Avhite stars. Then 

 we have the Solar stars, like the Sun, which are yellowish, and 

 present spectra delicately ruled from end to end by absorption 

 lines of metallic vapours ; the lines of hydrogen are also there, 

 but are not so prominent as in the Sirian stars. Besides these 

 we have reddish stars, called by Lockyer Antarian stars, whose 

 spectra are crossed by dusky bands or flutings of absorption, as 

 well as fine lines. Finally, we have the deep red stars called by 

 Lockyer Carbon stars, from lines and flutings due to carbon 

 compounds being prominent in their spectra. The white stars 

 are considered to be the hottest, the yellowish stars of medium 

 temperature, and the red the coolest. 



Now let us consider for a moment what all this means. We 

 have in the universe of stars an immense number of bodies all 

 differing from each other, not only in size and in rapidity of 

 motion, but in temperature and in physical constitution. They 

 form, indeed, a complete series, all the different forms passing 

 gradually into each other. Let us run over them. First we 

 have a nebula, where matter exists in its most diffuse form ; 

 then a stellar nebula, which is somewhat more condensed ; next 



