390 Mr. Pond and M. Bessel. 



fixed stars, arising from the discovery of a bc?iding in the tele- 

 scope affixed to his meridian circle : and of such a magnitude 

 as to account for all the discordances which existed between 

 his observations and those of Mr. Pond. — We have nothing 

 to do with the comparative merits of these two distinguished 

 astronomers, or of the celebrated artists by whom their re- 

 spective instruments were made : but, as we wish to guard the 

 public, at all times, against viisrep7-esentation, we think it our 

 duty to contradict the above report; which we now do on the 

 authority of the above-mentioned gentleman. 



When M. Bessel, in the year 1820, received the present meri- 

 dian circle from the hands of M. Reichenbach, he set to work 

 immediately in the only proper way in which observations can be 

 sately conducted: which was by endeavouring to cliviinate the 

 errors of the instrument. He minutely examined the divisions, 

 and the centering of the circle, the form and regularity of the 

 axes, and (what had not been done, we believe, by any for- 

 mer observer) instituted a series of observations in order to 

 determine whether any error could arise from the bending of 

 the telescope. All these points he investigated with his usual 

 accuracy and ability ; and the results have long ago been given 

 to the woi'ld in various publications : but, the detail was 

 reserved for the 7th part of his " Obsei'vations," where he has 

 show n the steps of each process, and given tables and formulas 

 for correcting the errors arising from these sources. — It is 

 needless to say that these corrections are properly applied in 

 the formation of his catalogue, in the same manner as the 

 index-eiTor, or any other correctional error is applied in the 

 formation of the Greenwich Catalogue : and the two catalogues 

 can only be compared as thus corrected. 



The error, arising from the bending of the telescope, he 

 found, at a maximum, to be l".ll; as stated upwards of a 

 twelvemonth ago in Bode's Astronomische Jahrbiich, and in- 

 serted in one of the former numbers of our Journal. But, 

 this correction (he justly remarked) instead of reconciling the 

 two catalogues, only made the dijfference greater*'. M. Bessel 

 has not communicated any particulars beyond these, nor any results 

 more recent than those above mentioned ; in fact, his cmrespon- 

 dent was referred to the very works above alluded to, for a mo}-e 

 full explanation of the subject of his letter. And, it is evident 

 that this correction of one second (which, by the by, has been 

 already applied in the formation of his catalogue, and there- 

 fore, in this view of the subject, is no error at all) could never 

 reconcile differences of several seconds which exist between 

 the catalogue of Mr. Pond, and not only that of M. Bessel, 

 * See Phil. Mag. for January 1823, page 29. 



but 



