STARS. 



iiiludes, have been diftributed into feveral clafles, called 

 magnitudes. 



The fii-ft clafs, or ftars of the firft magnitude, are thofe 

 which appear largeft, and may probably be neareft us. 

 Next thefe, are thofe of the fecond magnitude, and fo on to 

 the fixth, which comprehends the fmalleil ftars vifible to the 

 naked eye. All beyond thefe are called tehfcopic ftars. Not 

 that all the ftars of each clafs appear juftly of the fame 

 magnitude ; there is great latitude in this refpeft ; and thofe 

 of the firll magnitude appear almoft all different in luftre 

 and fize. Other ftars there are, of intermediate magnitudes, 

 which aftronomers cannot refer to one rather than another 

 clafs, and therefore they place them between the two. 



Procyon, for inftance, which Ptolemy makes of the firft 

 magnitude, and Tycho of the fecond, Mr, Flamftead lays 

 down as between the firft and fecond. 



Thus, intlead of fix feveral magnitudes, we may fay there 

 are almoft as many orders of ftars as there are ftars ; fuch a 

 difference being obfervable in the magnitude, colour, and 

 brightnefs of them. 



Whatever room there may be to hope, that we may fome 

 time or other be able to difcover the parallax of a few 

 among the fixed ftars, yet at the fame time it feems probable, 

 that we ftiall never be able to difcover any fenfible magni- 

 tude in their apparent diameters, which, even in Sirius, if 

 his native brightnefs is not lefs than that of the fun, muft 

 be confiderably lefs, whatever be his parallax, than the hun- 

 dredth, probably than the two hundredth part of a fecond ; 

 £b that it could fcarcely be diftinguiftiable with a telefcope, 

 upon the former fuppofition, that iliould magnify fix, or, 

 upon the latter, with one that fhould magnify twelve thou- 

 fand time?. Nor can we well expect to find their apparent 

 diameters from any occultation by the moon, fince the dia- 

 meter of a hundredth part of a fecond would be covered by 

 the moon, if it entered direftly, in lefs than the fiftieth part 

 of a fecond of time, and, therefore, a Itar can hardly enter fo 

 obliquely, as to appear to vanifti by degrees ; no ftar, pro- 

 bably, which the moon can pafs over, fubtcnding an angle 

 half fo great. Nor is it likely there can any thing be deter- 

 mined from occultations by any of the planets. And, 

 therefore, there feems to be little chance of difcovering with 

 certainty the real fize of any of the fixed ftars, and we muft 

 be content to deduce it from their parallax (if that fhould 

 ever be found) and the quantity of light which they afford 

 us, compared with that of the fun. Dr. Herfchel, however, 

 informs us, that with a magnifying power of 6.1.50, and by 

 means of his new micrometer, he found the apparent diameter 

 of a Lyrx to be o".355. 



The ftars are likewife diftin^iiiflied, with regard to their 

 fituation, into njlerifms, or conjiellutwtis, which arc nothing 

 'but aflemblages of feveral neighbouring ftars, confidcrcd 

 as conftitutingfome determinate figure, as of an animal, &c. 

 and denominated from it ; a divifion as ancient as the 

 book of Job, in which we find mention of Orion, and the 

 Pleiades, &c. See Constkllation. 



Befides the ftars thus dilliiiguiflicd into magnitudes and 

 conftellations, there are others not reduced to cither. Thofe 

 not reduced into couftcllations, arc called informa, (which 

 fee,) or unformed Jlars ; of which kind feveral, fo left at 

 large by the ancients, have been fince formed into new con- 

 fteliations by the modern aftronomers ; as Cor Caroli, by 

 Dr. Halley ; Senium Sobiefci, by Hcvelius, &c. 



In defcribing the particular ftars, it will be moft conve- 

 nient to begin with fuch as never fet in our climates, and we 

 may then refer the fituations of others to their pofitionswith 

 refpeft to thefe. 



The Great Bear is the moft confpicuous of the conftella- 



tions which never fet ; it confifts of fevfn ftars, placed Lke 

 the four wheels of a waggon, and its three horfes, except 

 that the horfes are fixed to one of the wheels. The two 

 hind-wheels are the pointers, which direft us to the pole- 

 ftar, in the extremity of the tail of the Little Bear : and fur- 

 ther on, to the conftellation Cafliopeia, which is fituated in 

 the milky way, where it is neareft to the pole, and which 

 confifts of feveral ftars, nearly in the form of the letter W. 

 The two northernmoft wheels of the Great Bear, or wain, 

 point at the bright ftar Capella, the goat, in Auriga. De- 

 fcending along the milky way from CafTiopeia, if we go to- 

 wards Capella, we come to Algenib, in Perfeus ; and a little 

 further from the pole we find Algol, or Medufa's head : but 

 if we take the oppofite direftion, we arrive at Cygnus, the 

 fwan ; and beyond it, a little out of the milky way, is the 

 bright ftar Lyra. The Dragon confifts of a chain of ftar* 

 partly furrounding the Little Bear ; and between Caffiopeia 

 and the Swan is the conftellation Cepheus. 



Near Algenib, and pointing directly towards it, are two 

 flars of Andromeda, and a third is a little beyond them. A 

 line drawn through the Great Bear and Capella paffes to the 

 Pleiades, and then, turning at a right angle towards the 

 milky way, reaches Aldebaran, or the bull's eye, and the 

 flioulders of Orion, who is known by his belt, confifting of 

 three ftars, placed in the middle of a quadrangle. Alde- 

 baran, the Pleiades, and Algol, make the upper, and Men- 

 kar, or the whale's jaw, with Aries, the lower points of a W. 

 In Aries we obfcrve two principal ftars, one of them with a 

 fmaller attendant. 



A line drawn from the pole, midway between the Great 

 Bear and Capella, pafies to the Twins and to Procyon ; and 

 then, in order to reach Sirius, it muft bend acrofs the milky 

 way. Algol and the Twins point at Regulus, the lion's 

 heart, which is fituated at one end of an arch, with Dene- 

 bola at the other end. 



The pole-ftar and the middle horfe of the wain direct us 

 to Spica Virginis, confiderably diftant : the pole and the 

 firft horfe nearly to Ardlurus, in the waggoner, or Boote». 

 Much further fouthwards, and near the milky way, is 

 Antares, in the Scorpion, forming, with Ardlurus and Spica, 

 a triangle, within which are the two ftars of Libra. The 

 Northern crown is nearly in a line between Lyra and Arc- 

 turus, and the heads of Hercules and Serpentarius are be- 

 tween Lyra and Scorpio. 



In the milky way, below the part neareft to Lyra, and on 

 a line drawn from ArClurus through the head of Hercules, 

 is Aquila, making with Lyra and Cygnus a confpicuous 

 triangle. The laft of the three principal ftars in Andronuda 

 makes, with three of Pegafus, a fquare, of which one of the 

 fides points to Fomalhaut, fituated at a confiderable diftance 

 in the fouthcrn fifli, and in the neighbourhood of the whale, 

 which has already been mentioned. 



By means of thefe allineations, all the principal ftars that 

 are ever vifible in Britain may beeafily recognifid. Of tiiole 

 which never rife above our horizon, there are feveral of the 

 firft magnitude ; Canopus, in the fliip Argo, and Achernar, 

 in the river Eridanus, arc the moft brilliant of them ; the 

 feet of the Centaur, and the Crofier arc the next ; and, ac- 

 cording to Humboldt's obfcrvations, perhaps fome others 

 may require to be admitted into the fame clafs. 



Thole ftars not reduced to clad'es or magnitudes, are called 

 nebulous ftars, being fuch as only appear faintly in clufters, 

 in form of little lucid nebul*?, or clouds. See Ni;hl i-.t:. 



Ptolemy fets down five cloudy ilar , viz. one at the ex- 

 tremity of the right hand of IVrfeus, which appears, tiimugh 

 the telefcope, thickly fet wi'h ftars ; one in the middle of the 

 Crab, called Prxfepe, or the Manger, in which Galileo 

 5 C 2 counted 



