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CHAP. XVI. THE DISTRIBUTION OF CHEMICAL GROUPS OF STARS. 



A. In Relation to Direction. 



THE most convenient way to consider the distribution of the various 

 chemical groups of stars, is to take the plane of the Milky Way as a 

 base, as we have already done regarding the stars merely as masses 

 of matter independently of all chemistry, and to note whether any 

 particular chemical species of stars congregates in the Milky Way or 

 avoids it. In this way the new molecular inquiry will be on all fours 

 with the older molar one. 



I will begin by leaving distances out of consideration. 



At present it will be sufficient for our purpose to deal with the 

 more generalised classification (already given on p. 72), which is as 

 follows : 



Highest Temperature. 



f Proto-hydrogen stars. 

 Gaseous stars < J 5 



I Cleveite-gas stars. 



Proto-metallic stars. 



Metallic stars. 



Stars with fluted spectra. 



Lowest Temperature. 



In discussing the work of other observers I have, as far as possible, 

 transposed the different notations employed into the chemical one given 

 above, and in some cases the two arms of the temperature curve will 

 require to be considered. 



The first attempt at such an inquiry as this was made in 1884, by 

 Duner,* who had made himself famous by his admirable observations 

 on two different classes of stars those which I have referred to as 

 being defined by carbon flutings in one case, and metallic flutings in 

 the other. His work was practically the only research on the carbon 

 stars the stars, that is, with carbon flutings. He was, naturally, 

 anxious to see how they were distributed, and he gave the number of 

 these stars in varying parts of the heavens in relation to the Milky 

 Way. He found that the numbers increased towards the Milky Way. 

 The table. I give will show the general result at which he arrived. 



* fitoiles de la troisieme Classe, p. 126. 



K 



