STELLAK CLUSTERS AND NEBULA. 



rays correspond with their dimensions in the direction at right 

 angles to those rays. 



In fig. 1 7 is represented a cluster observed and delineated by 

 Sir J. Herschel. It is situated at about 1| south of the celestial 

 equator, and about 38| east of the autumnal equinoctial point. 

 It occupies a space on the heavens, the diameter of which is equal 

 to the 300th part of that of the full moon. Sir John Herschel, 

 who observed it with a reflecting telescope of nine inch aperture, 

 describes its appearance as that of a most superb cluster of stars 

 of the fifteenth magnitude, so condensed towards the centre as to 

 become a perfect blaze of light. He compares it to a mass of fine 

 luminous sand. 



Nothing can be more striking than the different appearances 

 which the same objects have presented, when viewed by the 



Fig. IT. 



telescopes of Sir John Herschel and the more powerful instruments 

 constructed by the Earl of Rosse. In fig. 18 we have given the 

 same cluster as it appears in one of Lord Rosse' s telescopes. 



The stars which, in Sir John Herschel' s instruments, are crowded 

 together so as to produce a blaze of light, are completely separated 

 by the telescope of Lord Rosse. 



In fig. 19 is represented an object as delineated by Sir John 

 Herschel, which appears in his telescope as a fine oval nebula, the 

 length of which is about the eighth, and the breadth the tenth, 

 part of the moon's diameter. This nebula is situated a few 



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