THE COLOURED STARS ABOUT KAPPA CRUCIS. 



At the MontMy Meeting of tlie Eoyal Society, on tlie 2n(i 

 October, 1872, Mr. H. C. Eussell, the Government Astrono- 

 mer, read the following paper on the Coloured Cluster of 

 Stars about Kappa Crucis : — 



The beautiful cluster of stars generally known as the coloured 

 cluster about K. Crucis is but a small one, covering, according to 

 Sir John Herschel's estimate, only a 48th part of a square degree ; 

 but I know no cluster in the heavens equal to it in symmetry of 

 form and beauty of colour. There are many coloured clusters 

 brighter and more numerous, which at first sight seem more 

 beautiful, but not one whose beautiful features grow upon 

 acquaintance like this ; no other to which Herschel's glowing 

 description, " a superb piece of fancy jewellery," can be applied. 



In my recent survey of this cluster, facts have come to light 

 which would seem to give it new interest, and which probably 

 point it out as one of the stations from which astronomers will 

 gain knowledge of the distance of the starry systems. 



Some points in the history of the cluster are remarkable, and 

 may be here recorded for convenient reference, should some of 

 the probabilities prove to be facts. 



The first recorded observation of it is by Lacaille, in 1750. 

 He used a telescope 26 inches long, with an aperture of only half 

 an inch, and to him this object appeared as a nebula. This is an 

 important point, as will appear subsequently. 



No other observations were then made until Sir Thomas 

 Brisbane established the Parramatta Observatory, when it was 

 observed in the regular meridian work with the mural circle, the 

 telescope of which has an aperture of nearly 2 inches, and focal 

 length 25 inches, and was set down as " a cluster of 12 or 14 

 small stars, in the form of a rhomboid, very close together. Part 

 of this cluster forms a very perfect cone of mixed stars." 



It does not appear to have been examined with the transit instru- 

 ment or the equatorial, both of which are larger ; but about the 

 same time Mr. Dunlop examined it with a reflector of 9 feet focus 

 and 9 inches diameter, which he kept at his private house, and 

 he thus describes it (page 127, Phil. Trans., 1828) : — 



" Pive stars of the seventh magnitude, forming a triangular 

 figure, and a star of the ninth magnitude between the second and 

 third [in E. A.], with a multitude of small stars on the south 

 side." Unfortunately, he did not count them, nor give any other 

 description than that which I have quoted, but a good (though 



