STARS. 



diftance, which is about ai diameters, has continued the 

 fame for 2 1 years, while the angle of pofition has varied 

 confidcrably. On the 2 id November, 1781, the angle of 

 pofition was 40° 44' fouth following, or rather north pre- 

 ceding, fiRce the other ftar was afterwards found to be the 

 fmallerof the two ; and on the 15th April, 1803, the angle 

 of pofition was 30° 20' north preceding, having fuffered a 

 diminution of 10° 24' in 21 years and 145 days. From an 

 obfervation of Mayer's, however, in 1756, Dr. Herfchel has 

 found the angle of pofition for that year to be 54° 21' 37" 

 north preceding, which gives a motion of 24° 2' in 47 years 

 and 105 days. Hence he concludes, that a complete revo- 

 lution ie performed in about 708 years. 



For a catalogue, fuch as our limits would allow, of the 

 principal double ftars, fee the article Dol'bi.k Slars. 



For an account of clullering ilars, clulleru of itars, and 

 groups of ilars, and alfo treble, quadruple, quintuple, and 

 multiole lyftems of ftars, we rauft refer to the articles 

 Galaxy and Heavens ; and for a more particular detail, 

 and catalogues of them, to Dr. Herfchel's papers, or to the 

 2d volume of Fergufon's Aftronomy, by Dr. Brewfter. 



Stars, Infulatcd, a name applied by Dr. Herfchel to 

 thofe celeltial bodies which are in a great degree out of 

 the reach of the attractive force of other ftars, fuch as our 

 Sun, Arfturus, Capella, Lyra, Sirius, Canobus, Markab 

 Bellatrix, Menkar, Shedir, Algorah, Propus, and probably 

 many others. It is obvious that no two Itars in the uni- 

 verfe can be altogether out of the fphere of each other's 

 attraction ; but in the cafe of Sirius and our fun, which, 

 upon the fuppofition that their mafles are equal, and that 

 the former has a parallax of i", would take 33 millions of 

 years to fall to one another by their mutual attion, we are 

 entitled to fay that they are infulated. Infulatcd ftars are 

 confidered by Dr. Herfchel as the centres of extenfive 

 planetary fyltems like our own ; an opinion which he de- 

 duces from analogy, and from the nature of other fidereal 

 combinations. Inllead of fuppofing, therefore, as has gene- 

 rally been done, that every ftar in the firmament is encircled 

 with planets, fatellites, and comets. Dr. Herfchel believes 

 that the infulated ftars alone are fursouiided with fuch 

 numerous attendants. 



Stars, called NchuU. (See Nebul;e, Nebulosity» 

 and the articles to which we have above referred.) Mr. 

 Michel! has ftiewn, from the computation of probabilities, 

 that it is many million million chances to one, that the ftars, 

 which appear to form double ftars, &c. clufters and nebulae 

 in the heavens, are really coUefted together into feparate 

 fyftems. In the cafe of the Pleiades, for example, he 

 computes that it is joo.ooo to i, that no fix ftars out of 

 the number of thofc that are equal to the fainteft of them 

 in fplendour, fcattered at random in the whole heavens, 

 fliould be within fo fmall a diftance from each other as the 

 Pleiades are. 



A fimilar opinion was maintained by profefibr Kant and 

 M. Lambert, who fuppofed that all the itars in the univerfe 

 are collefted into nebulie ; and that all the infulated or 

 fcattered itars which appear in the heavens, belong to the 

 particular nebula in which our fyftem is placed. Wc are 

 indebted, however, folely to the genius and induitry of 

 Dr. Herfchel, for perfecting thefe fagacious views, and fup- 

 porting them by a body of evidence amounting nearly to 

 demonftration. He has obferved the pofition, magnitude, 

 and (trufture of no fewer than 2500 nebulae. He generally 

 detefted them in certain direftions, rather than in others ; and 

 in many parts of the heavens there were vacant fpaces, both 

 preceding and following the nebulous itrata. Dr. Herfchel 

 fuppofes the nebula in Cancer, and that of Coma Berenices, 

 to belong to two ftrata which are nearcft the nebula of the 

 Milky Way. 



The foUovping catalogue of nebulse, copied from Dr. 

 Brcwiler's edition of Fergufon's Aftronomy, is founded 

 chiefly on the obfervations of Meflier, as given in the 

 " Connoiil'ance dcs Terns" for J 784, the more recent obfer- 

 vations of Dr. Herfchel being always added. The Jirjl 

 column contains the number of the nebulse, and the time 

 wiien the obfervation was made ; the fccond and third, its 

 right alccnfion and declination for that time, which are 

 more convenient than their longitude and latitude for finding 

 them on a celeltial globe. The fourth, its diameter in 

 degrees and minutes ; and the lalt, foine general remarks on 

 its appearance. All the nebulae in this clafs may be feen 

 with good telefcopes of a moderate iize. 



Catalogue of 103 Ncbulx-, the Pofitions of which have been determined by Meffier. 



