HO 



INORGANIC EVOLUTION. 



[CHAP. xvi. 



metallic, including a few metallic ones which have collected in the 

 galactic plane. In this he agrees with the prior observations to which 

 I have drawn attention. In the table which I now give the mean 

 proper motion is shown. 



Relation between Spectra and Proper Motions of Stars (Kapteyn). 



We find that the gaseous and proto-metallic stars increase in num- 

 ber as the proper motion decreases. We find also the ratio of the 

 metallic to the gaseous and the proto-metallic. We begin with a ratio 

 of 17, and end with something like a ratio of O4; so that the results 

 may be considered to be pretty definite. These results were obtained 

 by Kapteyn with 591 stars which were common to Stumpe's catalogue 

 of proper motions and the Draper catalogue dealing with spectra. 

 The general result may, therefore, be stated that at the nearest dis- 

 tance the metallic stars are seventeen times more numerous than 

 gaseous stars, and at the greatest distance they are not half the 

 number. 



Here again the question arises, how far the intrinsic brightness of 

 these bodies, in relation to their distance from us and the possible 

 greater or less extinction of light in space, has to be taken into con- 

 sideration. That is a problem which will require a considerable 

 amount of work in the future. It is rather remarkable that if we 

 take the stars with very great proper motion, very much greater than 

 the average, we find with regard to four that three of them are 

 undoubtedly metallic, but it is possible that the star 1830Groombridge, 

 which is always looked upon as the star which beats the record in 

 velocity seeing that it would travel from London to Pekin in about 

 two minutes, is not a metallic star.* 



* These stars are 



1830 Groombridge 

 2 2758 . . 

 S 578 . . 

 B.C. 583 . . 



7 '04 . . Gaseous or proto-metallic. 



5 -196 . . Metallic. 



4-0<!9 .. Probably metallic. 



3-7 - . Metallic. 



