136 Double Stars. 



is perhaps somewhat difficult for a list like the present, but since 

 it may now be seen elongated with a good 31 inch object-glass, 

 and is beautifully divided with my 5£ inches, it seems better 

 not to omit so celebrated a test. Sir W. Herschel considered 

 it, in 1781, as the most difficult but one of all his double stars; 

 in 1832 Smyth could see a black division, but nothing more 

 than an elongation, never even notched, from 1839 to 1852. 

 Secchi could only doubtfully divide it with the splendid Eoman 

 achromatic in 1855 ; in 1859 this was my own case with a power 

 of 460; but in 1860, when Dawes measured it at 0"*87, I suc- 

 ceeded in dividing it, and it is still widening, as I found it, on 

 June 3 last, well separated with 275. There is little difficulty 

 in finding it. A line from a Coronce (see No. 35) to S Bootis (No. 

 23), passes first through /3 Coronce, 4 mag*., and then, a little 

 further on, falls upon tj. The beginner will find it an excel- 

 lent method to prepare the focus of the telescope by adjusting 

 it as carefully as possible previously upon some of the closer 

 pairs in the neighbourhood, as given in the foregoing list. 



We now return to Hercules, where a line from a through $ (No. 

 25) carried more than as far again, points out ir, 3 mag., the 

 brightest of its vicinity, remarkable for its very fine deep yellow 

 hue ; immediately/, are two 4 mag. stars, the furthest of which, 

 in a line towards Wega, is 



39. p Herculis. 3"- 7. 308°-9. 4 and 5±. Bluish-white 

 and pale emerald. This beautiful pair seems to be only optical. 

 Smyth found it within the range of two inches of aperture. 



\ Herculis, a single 4 mag. star, a little nf B, is worth 

 looking at for its colour, a deep, dull orange, with my old 3 T 7 ^ 

 inches, but which I now see somewhat like that of Antares, 

 yellow encompassed by a scarlet glare. It is towards this part 

 of the heavens, according to Sir W. Herschel and Argelander, 

 that our Sun, with his whole attendant system, is being carried 

 by ''''proper motion^ through space. 



40. 95 Herculis t 6"'l. 261°*8. 5^ and 6. Light apple- 

 green and cherry-red : a beautiful and curious instance of dif- 

 ference in colour between stars of very nearly equal magnitude. 

 Secchi thinks the red the larger, the green the brighter of the 

 two. Notwithstanding the complementary character of the 

 tints, which might be thought to infer a connection, no motion 

 has yet been detected. To find this charming object, we must 

 have recourse to a fresh pointer, Al Tair, the lucicla of the con- 

 stellation Aquila, which we shall at once recognize as the 

 brightest star in the S.E. heavens, standing just E. of the left- 

 hand branch of the galaxy, between two 3 mag. attendants 

 7 n p and j3 s f. A line from 8 Herculis to Al Tair will pass, at a 

 little more than one -fourth of its length, through a group of 5th 

 mag. stars, of which the nearest to S is our object. 



