1823.] Declination of seme of the fixed Stars, 25S 



must be very nearly indeed the same within a moderate distance, 

 as within 15 degrees, for instance, of that point. Upon this 

 supposition, how can we possibly reconcile the great errors that 

 must have been committed in stars, adjacent as to polar dist- 

 ance, but of opposite right ascensions ? I do not wish to press 

 these remarks, in order to obtain greater confidence than they 

 deserve, for observations which can never be regarded with too 

 much suspicion ; but the arguments I have used appear to me to 

 follow logically from the data before us, and strongly to indicate 

 the probabihty that some cause purely astronomical has, at 

 least, some share in producing these unexpected deviations. 



3. The third group, a Herculis, a Pegasi, and Regulus, is still 

 more remarkable, being comprehended within two degrees of 

 declination, and two of the stars, a Herculis and a Pegasi,* 

 being within half a degree of each other. In this group 

 u Pegasi is at least 3^^ south of its predicted place, whereas the 

 other two stars have not deviated much more than 0*5'''' to the 

 south. 



4. a Orionis, a Serpentis, and Procyon, furnish an example 

 equally striking, they being within less than 2° of declination 

 from each other ; a Serpentis is exactly in its predicted place, 

 while a Orionis and Procyon are each of them at least 2'' to the 

 south. 



5. Higel, Spica Virginis, and Sirius, are not contained within 

 so short an arc as the former groups, nor are their places so well 

 determined, on account of their proximity to the horizon ; but 

 they afford another instance of the inequality of southern devia- 

 tion, in stars having nearly the same polar distance, but opposite 

 right ascensions. 



But leaving the considerations suggested by these groups of 

 stars, let us examine more minutely the different hypotheses that 

 may be formed on the supposition, that the whole of these devia- 

 tions depends on error of observation caused by some defect in 

 the instruments employed : this investigation becomes the more 

 necessary, as it does not appear that Dr. Brinkley, with his 

 instrument at Dublin, has met with similar discordances. 

 Admitting the accuracy of the observations of Bradley to form 

 the ground-work of this inquiry, there are then two distinct 

 hypotheses, that may be formed by those, who are inclined to 

 maintain, that the proper motions of the stars are uniform ; and 

 that the discordances in question have their source, not in any 

 astronomical cause, but in some erroneous system of observa- 

 tion. Of the observations from which the catalogues of 1813 

 and of the present year have been computed, we may suppose 

 the one or the other to be erroneous. Let us consider the con- 

 sequences of each hypothesis. 



Let us first suppose the error to be in the observations of 1813. 



• The lunar nutation of « Pegasi was nearly a minimum at each period. 



