SECT, xxxvn.] NEBULA BOUND n ARGUS. 443 



far superior to the Nubecula Minor in every respect, though 

 they are similar in internal structure. The former consists 

 of large tracts and ill-defined patches of irresolvable nebulae, 

 and nebulosity in every stage of resolution, up to perfectly 

 resolved stars like the Milky Way; and also of regular and 

 irregular nebulae, properly so called ; of globular clusters in 

 every stage of resolvability ; and of clustering groups suffi- 

 ciently insulated and condensed to come under the designa- 

 tion of clusters of stars. Of these the nebula known as 

 Lacaille's 30 Doradus is too remarkable to be passed over. 

 It is very large, situate within the Nubecula Major, and 

 consists of an assemblage of nearly circular loops uniting in 

 a centre, in or near which there is a circular black hole. 

 In short, for the number and variety of the objects, there is 

 nothing like this cloud. Within an - area of only forty-two 

 square degrees, Sir John Herschel has determined the 

 places, and registered 278 nebulae and clusters of stars, with 

 fifty or sixty in outlying members immediately adjacent. 

 Even the most crowded parts of the stratum of Virgo, in 

 the wing of that constellation, or in Coma Berenices, offer 

 nothing approaching to it. It is evident, from this, that 

 from the intermixture of stars and unresolved nebulosity, 

 which probably might be resolved with a higher optical 

 power, that the nubeculae are to be regarded as systems sui 

 generis, and which have no analogies in our hemisphere. 



Next to the Magellanic clouds the great nebula round T) 

 Argus is one of the most wonderful objects of the southern 

 sky. It is situate in that part of the Milky Way which lies 

 between the Centaur and the body of Argus, in the midst of 

 one of those rich and brilliant masses, a succession of which 

 is so curiously contrasted with the profoundly dark adja- 

 cent spaces, and surrounded by one of the most beautiful 

 parts of the southern heavens. Sir John Herschel says : "It 

 would be impossible, by verbal description, to give any just 

 idea of the capricious forms and irregular gradations of 

 light affected by the different branches and appendages of 



