584 



Marvels of the Universe 



in dealing with double Stars, many of which exhibit the curious and beautiful phenomenon of 

 " complementary colours." Perhaps before going any further, I ought to explain the two phrases 

 just used, namely, " double Stars " and " complementar_v colours." 



When one gazes upwards at the sk^-, with the naked eye or an opera-glass, all the Stars we look 

 at appear as single points of light ; but a telescope will often show that we are looking at two Stars 

 so closely side by side that inadequate optical assistance, or none at all, makes them appear to be 

 only one Star. The larger the telescope, the greater the number of the Stars, apparently single, 

 which are found to be double. As a matter of fact, several thousand Stars are now known to be 

 really pairs of Stars. But this is not the whole case. A certain number of Stars, seemingly single 

 to the naked eye, or in a small telescope, are found, when examined with a larger telescope, to be 



i'lWtO f}u] 



A photograph of the b( 

 They are about an inch long 

 trolled by the slender body. 



THE W 



autiful winss. showj 

 but the flight of th 



[//'/,';// Mnin. y>.,v.. /■■. /:..N'. 



NGS OF THE LACE-WING FLY. 



.■ins the delicate net-like tracery of veins from which the fly derives its name, 

 nsect is slo\v and heavy, as though their e-'cpanse was too great to be con- 



triple ; that is to sa}', one becomes three, whilst there are such combinations as quadruples, quin 

 tuples, se.xtuples. After this we talk of them simply as " multiples." 



I must not go too much into details as regards these matters, or I should get too far astraj' from 

 the main point of this article, which is Coloured Stars. 



The second definition which I said it was expedient to present was the term "complementary 

 colours." In order to understand this, the reader must be reminded that if we take a source of 

 pure white light to start with, and pass a beam of it through a prism, we find the emergent beam of 

 light is transformed into a coloured beam, showing various gradations of colour between violet at 

 one end of the emergent beam and red at the other end. The various intermediate hues pass into 

 one another in beautiful succession, and the result is the well-known spectrum which we used to 

 regard as made up of seven colours, but which scientific men, following Sir David Brewster, often 

 now only regard as consisting of three colours, to be called truly primary, namely, yellow, red and 

 blue ; and that the other colours are no more than an admixture of these primary tints. If in white 



