Mr, Pond on the C/uinges in the [Oct. 



t)f which thr6e are found to the north, and three to the south of 

 their computed places. These inequalities may appear at first 

 sight to be wholly accidental ; but if we pay attention to the 

 right ascension, we shall find that the three which appear to 

 the northward, are situated in that part of the heavens as to 

 right ascension where the southern deviation is the least per- 

 ceptible, and that the three which appear to the southward, are 

 in that part as to right ascension where the southern deviation 

 is the greatest. But of these six stars there are two, a Cassio- 

 peiae, and y Ursae Majoris, which deserve further consideration. 

 These two stars are within less than one degree of each other in 

 polar distance, and consequently pass over the meridian at 

 nearly the same altitude. Ihe observations of Bradley on the 

 stars north of the zenith are not so numerous as could be wished ; 

 but each of the two stars in question was observed by him about 

 five times towards the year 1753 ; that is 60 years from the 

 date of my catalogue of 1813. I have carefully recomputed the 

 predicted places of these stars, and I find a Cassiopeiae not less 

 than 1-5'' to the south of its predicted place, and y IJrsae Majoris 

 half a second to the north. Now I am quite at a loss to conceive 

 how this difference in so small an arc can arise from error of 

 observation, and I can only attribute it to that cause, whatever 

 it may be, which seems so generally to depend not on the polar 

 distance, but on the right ascension of the star. 



2. The second group which I shall consider, contains the 

 stars a Arietis, Arcturus, and Aldebaran, comprehended within 

 an arc of about six degrees and a half. Of these three, Arc- 

 turus alone has yet been observed by reflection ; but from the 

 present very perfect state of the Greenwich circle, which the 

 method of reflection has enabled me to ascertain, it cannot be 

 doubted that the places of the two other stars are well deter- 

 mined.* In Arcturus the southern deviation is nearly insensi- 

 ble, but in the two other stars it is very considerable, being in 

 each not less than 1*5''. Now these three stars, but particularly 

 the two latter, are among those that have been most assiduously 

 observed by Bradley and myself, at each of the three periods. 

 Let us suppose then, if it be possible, that the whole of these 

 tleviations arise from error of observation ; or, in other words, 

 that no systematic deviation has really taken place in the stars, 

 but that their proper motions are uniform. Then we must admit 

 that the mural quadrant and the mural circle have at each period 

 given the polar distance of Arcturus correct, or at least subject 

 to the same constant error ; and as this star has been observed 

 at each period, at all times of the day, and at all seasons of the 

 year, the observations may be considered as perfectly exempt 

 from accidental error. It will I believe be readily conceded that 

 both instruments are so far perfect, that if the error be either 

 nothing, or a given quantity at one point of the arc, the errors 



• This has been confinned by subsequent observation. 



