ANNULAll NEBULAE. 



is described as a bright round nebula, forming almost a disc 15' 

 diameter, surrounded by a very feeble atmosphere. (Herschel.) 



Fig. 27. 



Fig. 28. 



84. Annular Nebula. A very few of the nebulae have been 

 observed to be annular. Until lately there were only four. The 

 telescopes of Lord Rosse have, however, added five to the number, 

 by showing that certain nebulae formerly supposed to be small 

 round patches are really annular. It is extremely probable, that 

 many others of the smaller class of round nebulas will prove to be 

 annular, when submitted to further examination with telescopes 

 of adequate power and efficiency. 



In fig. 29 one of this class is given, the situation of which is 

 (n A S h 47 m N P D 57 11') between the constellations of Gemini and 

 Cancer. This object, drawn by Sir J. Herschel, is the annular 

 nebula between /3 and 7 Lyra). He estimates its diameter at 

 6" -5. The annulus is oval, its longer axis being inclined at 57 to 

 the meridian. The central vacuity is not black, but filled with a 



Fig. 29. Fig. 30. 



nebulous light. The edges are not sharply cut off, but ill defined ; 

 they exhibit a curdled and confused appearance, like that of stars 

 out of focus. He considers it not well represented in the drawing. 



29 



