530 Astronomical Society, 



the positions observed at Geneva are in general a very little advanced 

 in the sense of the comet's motion in respect of those observed at 

 Berlin. M. Gautier thinks the results plainly indicate that a dimi- 

 nution is required to be made in the value of the mass of Mercury 

 adopted by M. Bremicker in calculating the effects of the perturba- 

 tions; and this is also the opinion of Encke : but M. Valz, who 

 observed the comet at Marseilles, from the 23d of November to the 

 16th of December, is of a contrary opinion. The observations of 

 the latter, it may be remarked, confirm entirely a circumstance re- 

 marked on a former occasion by himself, and also by Struve ; namely, 

 the contraction of the nebulosity in proportion as the comet ap- 

 proaches to the sun. 



On Ptolemy's Catalogue of Stars. By Francis Baily, Esq., Vice- 

 President of the Society. 



The catalogue of stars, which goes under Ptolemy's name, will 

 always be interesting to the astronomer, as containing the first 

 record of the state of the heavens. The precise epoch for which it 

 was formed is not clearly ascertained. Ptolemy himself says, that 

 it is reduced to the first year of the reign of Antoninus, which cor- 

 responds to the year a.d. 138; but there is some mistake or con- 

 fusion, on this point, which has led many persons to believe that 

 Ptolemy himself did not actually make the observations from which 

 the catalogue was deduced, but merel)' reduced, or brought up, a 

 more ancient catalogue of Hipparchus, by means of an erroneous 

 precession, to his own time. It is very evident that the longitudes 

 of all the stars in Ptolemy's catalogue are above 1° too great ; but, 

 from what cause this has arisen, it is not my object here to inquire. 

 The point to which, in the present view of the case, I am more de- 

 sirous of directing attention is, how far the existing editions of that 

 work may be considered as faithful transcripts of the catalogue as 

 it issued from Ptolemy's hands. 



This important question can only be decided by a careful exami- 

 nation of various manuscripts, and by comparing the discordant 

 readings with the actual positions of the stars as determined from 

 modem observations. Unfortunately the public have not been in 

 possession of much varied information on this head, the manuscripts 

 hitherto employed having, until lately, been confined to three only ; 

 to which two others have been recently added, as I shall presently 

 explain. But all these are, in many cases, so grossly discordant, that 

 it would appear, at first sight, almost a hopeless task to reconcile the 

 different readings that present themselves, or to account for the in- 

 troduction of so many discrepancies in so small a jjortion of Ptolemy's 

 great astronomical treatise. The five sources of information here 

 alluded to are, 



1st. The Latin translation published by Liechtenstein at Venice, 

 in 1515 ; the name of the translator Is not known, nor Is it stated 

 whence the manuscript was obtained. The translation, however, 

 bears Internal evidence of having been made from an Arabic manu- 

 script, and throws great light (as I shall presently show) on the sub- 

 sequent translations and editions from the Greek manuscripts. 



