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LXVIII. On the apparent Place of the Pole-Slar. By Francis 

 BAiLy, Esq. 



JL HE following tables, showing the apparent place of the pole- 

 star for every day of the years 1820, IS21, and 1822, were lately 

 published at Dorpat in Livonia, by Dr. Struve, the director of the 

 observatory at that place. They are computed from the for- 

 mulae and tables given by M. Bessel in various periodical works, 

 whicli are not generally known or read in this country: and 

 therefore tlie following account of them may perhaps be accept- 

 able to the public. 



It is well known to the practical astronomer that the pole- 

 star, on account of its magnitude, and proximity to the pole, can 

 be seen (with telescopes of no very considerable power) at all 

 times of the year, by day as well as by night : so that, when the 

 weather is favourable, it may be observed on the meridian twice 

 within every twenty-four hours. On account of the extensive use 

 to which such observations may be applied, it has become de- 

 sirable that the apparent position of this star in right ascension 

 and declination should be accurately determined for that precise 

 moment in every day in the year, when it passes the meridian. 



The tables, which follow, have therefore been calculated, for 

 that purpose, by Dr. Struve abovementioned, and Dr. Walbeck 

 the director of the observatory at Abo in Finland. The places 

 of the star were calculated by each of them separately for every 

 fifth day ; and the values for the intermediate days were inter- 

 polated, after applying for each separate day the correction de- 

 pending on the moon's longitude. The method of deducing 

 these values, 1 shall now proceed to explain. 



The mean place of the pole-star for the 1st day of January in 

 any given year (denoted by 1815 -|-/, where / denotes the num- 

 ber of years from 181.5) is first deduced from the formulae given 

 by M. Bessel, in bis Finidamenta Astronomice, page 30G : one 

 of which formulae serves to determine the right ascension of the 

 star, and the other its declination. They are as follow : 



Vol. 55. No, 266. June 1820. N n whence. 



