291 



VII. 



NEBULOUS SPOTS. ARE THESE ONLY REMOTE AND VERY 



DENSE CLUSTERS OF STARS ? THE TWO MAGELLANIC 



CLOUDS, IN WHICH CROWDED NEBULOUS SPOTS ARE 

 INTERSPERSED WITH NUMEROUS STELLAR SWARMS. 

 THE SO-CALLED COAL-SACKS OF THE SOUTHERN HEMI- 

 SPHERE. 



AMONG the visible cosmical bodies occupying the regions 

 of space, besides those which shine with stellar light (whether 

 self-luminous, or illumined like planets, stars isolated or in 

 multiple groups, and revolving round a common centre of 

 gravity), there are also masses which present a faint and 

 milder nebulous light. 1 These bodies, which appear at one 

 time as sharply defined, disc-formed, luminous clouds, at 

 another as irregularly and variously shaped masses, widely 

 diffused over large spaces, seem to the naked eye, at first 

 sight, to be wholly different from those cosmical bodies of 

 which we treated fully in the last four sections of the Astrog- 

 nosy. In the same way that there is an inclination to infer 

 from the observed and as yet unexplained motion of the 

 visible cosmical bodies* the existence of others hitherto in- 

 visible, so the knowledge gained as to the resohability of a 

 considerable number of nebulous spots has recently led to 



1 Cosmos, vol. i. pp. 69-73, 75 and 131 ; vol. ii. p. 710 ; 

 vol. iii. pp. 44-49, 189, 208 and 220. 

 * Cosmos, vol. iii. pp. 252-254. 

 YOL. iv. B 



