S9 



the College Observatory with the eight feet Circle and Transit In- 

 strument. The equinoxes observed were those commencing Autumn 

 1822, and ending Spring 1825. It is believed these right as- 

 censions have been determined with considerable exactness. They 

 have therefore been applied to investigate, by help of the quantities 

 of annual precession as now found, the proper motions in right as- 

 cension of the principal fixed Stars. The catalogue in North polar 

 distance formed by observations with the eight feet Circle, has also 

 been used for finding the proper motions in North polar distance. 

 There is reason to expect that these proper motions will be found 

 hereafter more exact than any which have hitherto been given. 



It may be right to mention, that in forming the catalogue of right 

 ascensions, the constant of aberration was taken =20 ',36, and that 

 of nutation = 9"25, as I had found by former observations and in- 

 vestigations. 



This Catalogue in right ascension differs so much from the Cata- 

 logue in right ascension as given in the Nautical Almanacs for 

 1827 and 1828, that it appears necessary to notice this circum- 

 stance. In some of the Stars the difference amounts to ^ of a 

 second of time, or 6" in space. The determination of the absolute 

 right ascension of a Star is certainly a very delicate investigation, 

 but still with the present improved means of observing it was not to 

 be expected so great a difference would be found. It is an object of 

 interest to ascertain which determination is nearer the truth. M. 

 Bessel's recent Catalogue ("Astronomische Nachrichten, No. 78,) 

 is between the two, but somewhat nearer to mine. I can only 

 refer to the small mean errors of my Catalogue in each of the three 

 years, which tend to establish its exactness. — There appears no 

 cause whence a constant error should arise, unless from the different 

 degrees of temperature at the Vernal and Autumnal Equinoxes, and 



