On the apparent Place of the Pole- Star. 403 



where he has moreover given tables and rules for determining 

 the apparent places of 14 of the principal stars observed by Brad- 

 ley, at the time they passed the meridiaji of Greenwich, for the 

 years 1750 to 1762. And in the first part of his Astronomical 

 observations above mentioned, he has given tables and rules for 

 determining the apparent places of Dr. Maskelyne's 36 principal 

 stars ai the lime of their culmination, for every tenth day of the 

 year. As these stars are generally obse'!^vcd when on, or near, 

 the meridian, it certainly would be desirable that their apparent 

 places should be given for the time of their culmination, ra^.d not 

 for noon, a"^ is usually practised. 



I have thought it the more necessary to make these observa- 

 tions, in order to obviate any false impression which may arise 

 from comparing the values given in this table, with those which 

 are now given for the first time in the Nautical Almanac for 1S22. 

 For instance, the app.arent place of the pole-star on June 29, 1 822 

 is stated in the Nautical Almanac to be yR = 0'\ 57'. 19",6, 

 D = 8S'. 21'. 29",fi ; whereas, in the following tables, it is stated 

 to be 751 = 0''. 57'. 20",8, D = S8°. 21'. 29",0. Now various 

 reasons may be assigned for this, and other differences : in the 

 first place, the computations are not made for the same moment 

 of time ; secondly, the mean place, at the beginning of the year, 

 is not the same in each; and thirdly, the corrections are more 

 numerous in the latter than in the former. Still however this 

 will not account for the whole of the differences observable in 

 the two tables. 



As the pole-star is sometimes obscured, when other principal 

 stars in its neigJibourhood, such as 8, /3, y UrscB minoris and 

 y Cephei, are visible, the observations of which might be made 

 available to many useful purposes, would it not be desirable to 

 attempt the correction of the places of those stars in a similar 

 manner ? Some of the stars, also, situated still further from the 

 pole, and innnediately in the zenith, such as y Draconis and 

 others, of which considerable use is made in practical astronomy, 

 may likewise be subject to variations not hitherto understood ; 

 but vvhicli may hereafter )ield to the investigations of the analyst. 

 In shorf, is it too much to presume that what is called the proper 

 motion of a star may at some future time be resolvable into ge- 

 neral forumlae ; whereby its value may be asceitained in the same 

 way as that of aberration and nutation ? These subjects, how- 

 ever, 1 shall leave at present for the consideration of those who 

 have leisure and disposition for the investigation : contenting my- 

 self with having directed the attention of the public thereto. 



It is scarcely necessary to add that the following formula? for 

 the right ascension must be divided by 15, if it he required to 

 determine it in time. 



N n 2 Formuler 



