iXXXVl NOTES. 



t 404 ) p. 235. Annular nebula : (Cape Observ. p. 53 ; Outlines of Astr. p. 

 602); Nebuleuse perforce: (Arago, in the Annuaireforl842, p. 423) ; Bond, 

 in Schum. Astr. Nachr. No. 611. 



( 405 ) p. 235. Cape Observations, p. 1 14, PI. vi. fig. 3 and 4 ; compare 

 also No. 2072, in the Phil. Trans, for 1833, p. 466. See Lord Rosse's 

 drawings of the ring-nebula in Lyra, and of the singular crab-nebula in Nichol's 

 " Thoughts on the System of the World," p. 21, PL iv. ; and p. 22, PI. i. 

 fig. 5. 



t 406 ) p. 236. Regarding the planetary nebula in Ursa major as a sphere, 

 and supposing it placed at a distance from us not more than that of 61 Cygni, 

 its apparent diameter of 2' 40" would imply an actual diameter seven times 

 greater than that of the orbit of Neptune (Outlines, 876). 



(^T) p. 236. Outlines, p. 603 ; Cape Observations, 47. An orange-red 

 star of the 8th magnitude is near No. 3365, but the planetary nebula still 

 appears of a deep indigo-blue when the red star is not in the field of the tele- 

 scope : the colour is therefore not the effect of contrast. 



C 408 ) p. 236. Kosmos, Bd. iii. S. 173, 299, and 309 (Engl. edit. p. 115, 

 208209, Note 348). In more than 63 double stars the companion and 

 the principal star are both blue or bluish. Small indigo-blue stars are inter- 

 mingled in the superb many-coloured star-cluster No. 3435 of the Cape Cata- 

 logue (Dunlop's Cat. No. 301). There is an entirely uniform blue cluster of 

 stars in the southern heavens (No. 573 of Dunlop, No. 3770 of John Her- 

 schel). It has 83' diameter, with projections which run out to 8' of length : 

 the stars are from the 16th to the 14th magnitude (Cape Observ. p. 119). 



C 409 ) p. 236. Kosmos, Bd. i. S. 88 and 387 (Engl. edit. p. 76, Note 31). 

 Compare Outlines, 877. 



( 41 ) p. 236. On the complexity of the dynamic relations in the partial 

 attractions in the interior of a spherically round star-cluster, which in weak 

 telescope* appears as a round nebula denser towards the centre, see Sir John 

 Herschel, in Outlines of Astronomy, 866 and 872; Cape Observ. 44 and 

 111113 ; Phil. Trans, for 1833, p. 501 ; and Address of the President in 

 the Report of the Fifteenth Meeting of the British Association, 1845, p. xxxvii. 



( 4n ) p. 237. Mairan, Traite de 1'Aurore boreale, p. 263 (Arago, in the 

 Annuaire for 1842, p. 403413). 



( 412 ) p. 238. Other instances of nebulous stars are only from the 9th to 

 the 8th magnitude; as, for example, No. 311 and No. 450 of the Catalogue 

 of 1833, fig. 31, with photospheres of 1' 30" (Outlines, 879). 



( 413 ) p. 238. Cape Observations, p. 117, No. 3727, PL vi. fig. 16. 



