SECT. XXXVI. ELLIPTICAL NEBULAE.' 413 



heavens consist of spherical or elliptical forms presenting every 

 variety of elongation and central condensation. Of these a great 

 number have been resolved into stars, and a great many present 

 that mottled appearance which renders it certain that an increase 

 of optical power would decompose them. Those which resist do 

 so on account of the smallness and closeness of the stars of which 

 they consist. 



Elliptical nebulas are very common ; by much the finest may 

 be seen near the star v in the girdle of Andromeda. It is visible 

 to the naked eye, and has frequently been taken for a comet. 

 With a low optical power it has the spindle-shaped form of fig. 6, 

 plate 5, the brightness being at first gradually and then rapidly 

 condensed towards the centre, so that it has been compared to a 

 star shining through horn, but had never appeared resolvable even 

 with high optical powers till Mr. Bond examined it at the obser- 

 vatory of Cambridge in the United States. He found that its 

 brightness extends over 2^ degrees in length, and more than a 

 degree in breadth, including two small adjacent nebulas ; so that it 

 is oval. It is strongly and rapidly condensed into a nucleus on 

 its northern side ; and although it was not all resolved, it was 

 seen to be strewed over with star dust, or extremely minute visible 

 stars, which leaves not a doubt of its being a starry system. The 

 most remarkable part of Mr. Bond's discovery are two very 

 narrow dark lines which extend along one side of the oval parallel 

 to its major axis. These black streaks, difficult to distinguish, 

 indicate a stratified structure, and are not the only instance of 

 that arrangement in nebulas. Fig. 1, in plate 9, is from Mr. 

 Bond's drawing of this nebula. 



Multitudes of nebulas appear to the unassisted eye, or are seen 

 with ordinary telescopes, like round comets without tails ; but 

 when viewed with powerful instruments they convey the idea of 

 a globular space, insulated in the heavens and full of stars, con- 

 stituting a family or society apart from the rest, subject only to 

 its own internal laws. To attempt to count the stars in one of 

 these globular clusters, Sir John Herschel says, would be a vain 

 task ; they are not to be reckoned by hundreds. On a rough 

 computation, it appears that many clusters of this description 

 must contain ten or twenty thousand stars compacted and wedged 

 together in a round space, whose apparent area is not more than 

 a tenth part of that covered by the moon ; so that its centre, 



