56 Double Stars. 



on apparent brightness, is applicable, from tlie extreme minute- 

 ness of the measures required, and their rapid decrease and 

 disappearance with increasing distance, to so few cases, that 

 we still feel bewildered as at the entrance of a mighty labyrinth; 

 so very few are the known points, the unknown, practically 

 infinite. 



To find S, run a line N. from a, which will strike it at 10° 

 distance ; it will be the first conspicuous star in that direction, 

 and, though not large, the brightest in a considerable region. 



26. S Serpentis. 2"-8. 196°-2. 3 and 5. Bright-white 

 and bluish-white ; under the very best vision, both bluish. 

 Dembowski gives yellow tints, probably from his telescope. 

 Motion is suspected in this very fine pair, which may be found 

 by drawing a line through the two stars called Yed (see No. 15) 

 towards the right, and bending it a little upwards ; this will 

 pass, at some distance, through three stars, of the 3rd, 2nd, 

 and 3rd mags, the centre one, which is by far the brightest, is 

 a Serpentis ; the furthest is our object, 8. 



27. k Herculis. 81"-4. 9 0> 7. 5f and 7. Pale-yellow and 

 reddish-yellow. Probably stationary. To find it, run a line 

 through the "two heads," a Ophiuchi and a Herculis, and 

 bend it a little upwards ; at a considerable distance it will strike 

 upon /3 Herculis, 3 mag., the brightest star in a wide region ; 

 a little s p from /3 lies a smaller star, 7, in the unbent line 

 through the " two heads." Another line through /3 and 7, bent 

 a little upwards, falls upon several minute stars close together, 

 rather further from 7 than 7 is from /3 : k is the most to the W. 

 of these. It is also nearlv in a line from 7 Herculis to S Ser- 

 pentis (No. 26). 



28. 53 Ophiuchi. 41"-3. 192°-5. 6 and 8. Greyish and 

 pale blue. This beautiful object, which ^eems only optical, is 

 rather minute for the naked eye in twilight, but it is not diffi- 

 cult to find, as it lies due s of a, only 3° distant ; the space 

 between a Ophiuchi and a Herculis being about 5^°. 



The number by which this and other stars are designated, 

 is that assigned by Flamsteed, and denotes the place in his 

 catalogue, in the order, not of brightness, but of Right 

 Ascension. 



Before it sinks too far towards the horizon, we had better 

 turn to — 



29. 12 Ganum Venaticorum. Cor Oaroli. 19"-8. 227°. 

 2 1 and 6£. Flushed white and pale lilac, 1837'4. There is 

 some doubt about these tints. Herschel II. says, in 1830 or 

 1831, "with all attention, I could perceive no contrast of 

 colours in the two stars." His father calls them white, in- 

 clining to red ; Struve, in 1830, made them white ; Sestini, in 

 1844*5, yellow and blue; Smyth, again in 1850*5, full white 



