Clusters and Nebulae. 451 



faint and small, with a 7-inch object glass ; 1854, seen by 

 Chacornac at Marseilles ; 1855, November, December; 1856, 

 January, easily distinguished, even in moonlight, at Leipzig, 

 with a 6-feet telescope ; 1855, 1856, observed by Breen, with 

 the Northumberland telescope at Cambridge; 1858, February, 

 March, seen faintly at Gottingen with 6-feet achromatic ; 1861, 

 Konigsberg, 8 -feet heliometer, October 4, traces conjectured ; 

 November 3, in remarkably clear air, not a vestige of it, nor 

 had it been seen there up to 1862, April 2 ; 1861, October 3, 

 invisible in the great Copenhagen achromatic; 1862, January, 

 sought in vain with the great Foucault silver-on-glass reflector 

 at Paris, 27 inches in diameter, as well as by Hind and Secchi. 

 Nor was Lassell able to perceive it, even with 48 inches of metal, 

 in the pure sky of Malta ; the Poulkowa achromatic alone con- 

 tinuing to show some feeble appearance of it in 1861 and 

 1862. This is marvellous enough, but the wonder is in- 

 creased by the fact that a small star, only 1' distant from 

 it, has sunk, between 1852 and 1862, from 9*4 to 13 or 14 

 mag. The coincidence, to say the least of it, is sufficiently 

 strange to arrest our watchful attention, especially in con- 

 nection with Otto Struve's views as to the probability of vari- 

 able light, not only in certain parts of the nebula in Orion, but 

 in some of the minute stars involved in its extent. 



7. The Crab Nebula. — In the directions for finding No. 75 

 of our Double Star List (Intellectual Observer, Feb. 1863, 

 p. 55), the position of £ Tauri is pointed out : this star will 

 readily guide us to a nebula lying rather less than 1° np, which, 

 though inconspicuous in itself, has become well known from 

 the commonest of its portraits. It is No. 1 of Messier 's list, 

 having been discovered by him in 1758. He was observing the 

 position of a comet near £ Tauri, when he perceived it as " a 

 whitish light, elongated like the flame of a taper;" aud was 

 thus induced to undertake his useful Catalogue. Smyth re- 

 marks that it " was also a mare's nest to more than one astro- 

 nomical tyro in August, 1835, when on the look-out for the re- 

 turn of Halley's comet/'' The Admiral describes it as a large, oval, 

 pearly -white nebula, brightest towards the S . In Sir J. HerschePs 

 Catalogue, where it stands 357, it is stated to be 4' long, 

 3' broad ; very gradually a little brighter in the middle, and 

 resolvable. But a grand change was wrought in its aspect by 

 the three-feet speculum, which was the earlier fruit of the 

 Earl of Posse's labours ; he observes that " it is no longer an 

 oval, resolvable nebula : we see resolvable filaments, singularly 

 disposed, springing principally from its southern extremity, and 



not, as is usual, in clusters, irregularly in all directions 



it is studded with stars, mixed however with a nebulosity, pro- 

 bably consisting of stars too minute to be recognized." I have 



