2St On some new Tables oj' Abciralion and Nutation. 



fore the computations, wlitn once made for any particular 

 days in one year, may be considered as constant quantities for 

 the same days in any succeeding year. Whence, the only 

 variable parts of these expressions will be those which depend 

 on the sine and cosine of ft ; which will vary little during the 

 space of a hundred days. So that it will only be necessary to 

 com^Mie four values of each for any given year ; and to deduce 

 the values for the intermediate days, by interpolation. Sup- 

 plementary tables of diis kind would have formed a valuable 

 addition to those which M. Bessel has given. It would also 

 have been a considerable improvement, if the values of a, b,c, d, 

 had been divided by 15 so as to have given the corrections in 

 time, instead of in arc. 



With respect to the few stars which are observed at Green- 

 wich, and which are called (xar* s^oxvv) Greenmch stars, M, Bes- 

 sel has formed of/ier tables, more convenient for finding their 

 daily corrections. The constant use which is made of those 

 stars, in an observatory, requires that their corrections should 

 be given for everj/ day in the year. But it would be an end- 

 less task to give such corrections for the whole of the 500 stars 

 which I have alluded to in this letter. It was desirable there- 

 fore that a convenient mode should be jiiven for deducins those 

 values, as occasion might require. Such a mode is now pre- 

 sented by M. Besscl: and the astronomical world is much in- 

 debted to him, and his distinguished pupils at the observatory, 

 for this proof of their zeal and public spirit. It is gratifying 

 to see the patronage and protection which are afforded to young 

 men of science on the continent, and to view the rising talents 

 of those who are ambitious to pursue the ste}is of their illustri- 

 ous predecessors. Every attempt is encouraged which tends 

 to relieve the practical astronomer : and France, Italy, Por- 

 tugal, Germany, Russia, Denmark and Prussia nave each in 

 their turn set a laudable example, to this country, of the good 

 effects of this fostei'ing spirit ; which, however, tty seem very 

 loth to pursue. 



I am, gentlemen, 



Your obedient servant, 

 Gray's Inn, Oct. 18, 1822. FranciS Baily. 



P.S. — On referring to M. Schumacher's Aslron. HiUfs. for 

 1820, it appears that M. Bessel's mode is similar to that which 

 has been proposed by M. Gauss. But, no explanation is there 

 given of the steps of tlie process. 



Liv. d:s 



