254 Mr. J. N. Lockyer. On the Classification [Jan. 10, 



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I'm. 21. Light curve of a meteor-swarm during the various stages of condensation. 

 The numbers represent the spectroscopic groups, I being the least condensed, 

 and YII the most condensed. 



its existence as an nncondensed swarm, however, the increase of 

 luminosity of the swarm will be very steady ; hence there will first of 

 all be a gradual increase of luminosity ; this will be followed by a 

 rapid rise to maximum, and afterwards a steady fall, until finally all 

 luminosity disappears. 



The light curves being of this form, if we begin with two uncon- 

 densed swarms of equal masses and conditions, the curve for each will 

 be the same in length and in the point of maximum luminosity. It 

 will be a neck and neck race, and we shall have equal brilliancy, 

 similar colour and spectrum throughout. Such stars I call Class I. 



JTV. Binary Stars, Class!. Equal Magnitudes and Similar Colours (not 



Yellow), 



The first question is: Are there any such stars, for from the 

 existence of so many nearly equal double nebulae in the heavens we 

 should expect a large number. 



For the purpose of this inquiry I have used the Bedford Catalogue,* 

 and have limited myself to the stars which afford the strongest 

 evidence of being binary systems. In the absence of any spectro- 

 scopic survey of such systems, I am forced to content myself with 

 similar or nearly similar colours. 



The following is a list of the binary stars given by Smyth, in which 

 the magnitudes and colours of the components are almost identical. 

 I except for the present those in which both components are yellow 

 for a reason before stated. 



In these cases the two curves representing the lives of the com- 

 ponents will be identical, or nearly so, and will be as in fig. 21. One of 

 the components may have a somewhat smaller mass, and, therefore, a 

 shorter time of existence, as a self-luminous body, than the other, 

 but the magnitudes and colours may still be nearly equal, or suffi- 



* * A Cycle of Celestial Objects,' Smyth and Chambers ; 2nd edition, 1881. 



