VOL. LXXXVI.] PHILOSOPHICAL TRANSACTIONS. ' 7 17 



annexed to stars with a strict view to their order of brightness, they would now 

 be of considerable service ; but the intention of the astronomers who lettered 

 the stars seems only to have been to give them a name, by which to c:ill them 

 more readily, than by the descriptive method of pointing out their situation. 

 It was indeed natural enough to give the name a. to the brightest star, on ac- 

 count of its being the most remarkable in a constellation ; and we may admit 

 that with a few of the most conspicuous stars the letters a(3y would present 

 themselves in succession ; but whoever compares all the letters of the Greek, and 

 English alphabet that have been used, with the numerical magnitudes annexed 

 to the same stars, will immediately give up all thoughts of intended order. In 

 the constellation of Andromeda, which happens to lie before me, is found the 

 following arrangement : So^i, Ott^, AuuX, and dhc. In that of Hercules iS, ^xx, 

 7r9, fp, o-i/, TO, and h\ebhqcmz. 



It will be needless to point out the irregularities which take place in every 

 other constellation ; they go indeed so far, that it would be wrong to call them 

 irregularities, because certainly no order could be intended in the arrangement 

 of the letters. A doubt has even arisen whether any succession of brightness 

 might be argued from the very 1st, 2d, or 3d letters of the alphabet ; and when 

 we find them arranged thus : (3^ Cassiopae, ^px Cancri, y^ Aquilae, (3(^ Canis mi- 

 noris, A\ y Arietis, we can hardly think it safe to regard the order of letters as 

 of the least consequence. To which may be added, that in many constellations 

 «Py are all marked to be of the same magnitude, in which case again the order 

 of the letters can bring no information. And therefore, even in those cases 

 where the order of the letters agrees with the different magnitudes assigned to 

 them, the knowledge we can have of the former state of the heavens must be 

 derived from the magnitudes, and cannot be from the letters. 



It may in the next place be remarked, that if not the letters, at least the nu- 

 merical magnitudes affixed to the stars by astronomers, point out an order of 

 brightness ; and therefore contain my method already established. A succession 

 of the marks 1, 2, 3, 4, 5, &c. and other intermediate notations, which are to 

 be found in the British, and other catalogues, give us a long list of stars that are, 

 or should be, in a regular order of brightness, from a star of the 1st magnitude 

 down to one of the 8th or Qth. That these marks, denoting the magnitudes of the 

 stars, are of some use every astronomer will readily perceive ; but if we would 

 apply them to the purpose of detecting a change in the lustre of some suspected 

 star, the defect of this method will easily appear, and has already been shown in 

 the instance of <t Leonis. It was hinted before that the subject would recur 

 ao-ain, I shall therefore mention 2 other instauL-es, in the first of which the 

 common notation is sufficiently expressive. It will be so in all cases where a very 

 considerable change lakes place. Thus, j3 Persei being marked 2.3 m, and ^ of 



