280 aOLAR MOTION. 



Investigation n^o^»<**s of the stars when regulated in this manner, arft 



of the proper not QoUke the disposition by which the bodies of the solar 



mo^jon c gyg^gj^ jjpg governed. If we pursue this arrangement, it 



will be proper to consider the condition, and probable 



existence of such a centre of attraction. 



There are two ways in which a centre of attraction, so 

 powerful as the present occasion would require, may be 

 constructed : the most simple of them would be a single 

 body of great magnitude ; this may exist, though we 

 should not be able to perceive it by any superiority of 

 Ivstire; for notwithstanding it might have the usual 

 starry brightness, the decrease of its light arising from its 

 great distance would hardly be compensated by the size of 

 its diameter ; but to have recourse to an invisible centre, 

 or at least to one that cannot be distinguished from a 

 star, would be entirely hypothetical, and, as such, can- 

 not be admitted in a discussion, the avowed object of 

 which is to prove its existence. 



The second way of the construction of a very power- 

 ful centre, may be joint attraction of a great number of 

 Stars united into one condensed group. 



The actual existence of such groups of stars has al- 

 ready been proved by observations made with my largo 

 instruments ; many of those objects, which were looked 

 upon as nebulous patches, having been completely re- 

 solved into stars by my 40 and 20-feet telescopes. For 

 instance, the nebula discovered by Dr. Halley in the year 

 1714, in which the discoverer, and other observers after 

 him, have seen no star, I have ascertained to be a globular 

 cluster, containing, by a rough calculation, probably not 

 Ivis than fourteen thousand stars. From the known 

 laws of gravitation, we are assured that this clnster must 

 luvea very powerful attractive centre of gravity, which 

 may be able to keep many far distant celestial bodies in 

 control. 



But the composition of an attractive centre is not 

 limited to one such cluster. An union of many of them 

 will form a still more powerful centre of gravitation, 

 who.o influence may extend to a whole region o( scat- 

 ter«d stars. To prove that I argue entirely from observa- 

 tions, I shall mention that another nebula, discovered by 



Mr. 



