C 25 J • 



Mil. On the Dedrnation of the Fixed Stars. By Professor 

 Bessel. Sent from Konigsberg, 29th August 18^22*. 



ABOUT the middle of the last century, a collection of astrc- 

 nomical observations was made by Bradley, which does 

 not appear to have been followed up, after the death of that 

 great astronomer. In the Observatory at Greenwich, tlie ob- 

 serrations vrere indeed pursued with the same instruments ; but 

 those insti-uments, from continued use, had lost much of their 

 accuracy ; and even at Maskelnie's death had given erroneous 

 results. Other observatories either did not possess sufficient 

 means, or depended too implicitly on the Greenwich catalogue, 

 which was the onlv source fiom which astronomers derived 

 their information till the appearance of Piazzi's great work. 

 Through Piazzi, however, declinations were given, which ren- 

 dered the former doubtful : in fact, Maskelyne acknowledged 

 the defects of his mural quadrants, wliich, to the injury of 

 asti-onomy, had continued far too long without being dis- 

 covered. About tliis time observations with instruments be- 

 gan to be more frequent ; and in foct, those of Piazzi, Oriani, 

 Pond and Brinkley, showed an accordance in the declinations 

 of the stars, which could not be expected to b« siiipassed : al- 

 though at the same time it showed that mistakes might oc^ 

 cur, with those wlio were not accustomed to look alter them. 

 Besides, all the series of observations did not agree, till the 

 excellent Bohnenberger succeeded in showing the real cause 

 of error, in the repeating circles. The first suspicion of those 

 errors arose from the difference that was observed in the obli- 

 quity of the ecliptic at the two solstices. The sniiiller repeating 

 circles gave the obliquity at the winter solstice 8" to 16", and 

 the larger circles of Pia'zzi and Pimd 4-" to 8", smaller than 

 the oblTquity at the summer solstice; whilst the observations 

 of Bradley, Groombridge, and myself, gave them both alike. 

 The declinations of the stars wliich 1 observed with Cary's 

 circle, were altogether more southerly than those copipre- 

 hended in the catalogues above mentioned. But here niine 

 stood (juite alone; for Bradley's observations were too far di- 

 stant, to admit of their being comi)ared ; and, as fir as I know, 

 Groombridge has not published his declinations ot the tun- 

 damental stars. 



Bradley has maintained in liis celebrated paper on the Nu- 

 tation, that it is extremely difficult to make observations which 

 are to be depended upon in every case. The correctness ot 

 this remark I have had many opportunities of experiencing m 



* From Bodc's Aiiroiujiidsc/ic Jalnbuch lor W2o. 

 Vol, 61. No. 297. Jan. 1823. D the 



