MULTIPLE STARS. 



549 



the colours of many are due to absorption by the vapours of some of the rays ; 

 and the existence of certain vapours may cut off some, and at other times 

 other vapours may exist and cut off other rays, and so the colours may be 

 changed. Struve gives the following list of binary complements of 

 " multiple " stars : 



Pairs consisting of a blue and white principal star 

 and a light yellow principal star 



,, a yellow or red principal star . 



a green principal star 



53 

 52 

 52 

 16 



183* 



185* 



1836 



Fig. 619. Position of the two stars of y Virginia.* 

 171!) m '9 1802 



1819 



1326 



185*- 5 



Fig. 620. Position of the two stars of Castor.* 

 1751 1QOZ 1809 



Fig. 621. Position of the two stars off Ursae Majoris.* 



We need scarcely pursue this question farther, though many ideas 

 concerning the coloured stars will arise in every thoughtful reader's mind. 

 Supposing that every system has its sun or suns, can we fancy the effects of 

 a green or blue or violet sunlight a light unmixed ? To employ the 

 words of Sir John Herschel " It may be more easily suggested in words 

 than conceived in imagination what variety of illumination two suns, a red 

 and a green, or a yellow and blue one, must afford to a planet circulating 

 round either or what charming contrasts and graceful vicissitudes a red 



