5f 



Tlie quantity of proper motion for each of these Stars may be 

 separately investigated by means of the three fixed Stars Rigel, 

 « Orionis and « Cygni. — Taking the distances between Rigel and «, 

 Cygni for the common base of two spherical triangles, the vertices 

 of which are the places of the Star in 1755 and 1821. — The dis- 

 tance between these vertices is the whole proper motion of the Star 

 in 66 years. The part of this motion in N. P. dist. being applied to 

 the whole change of North Polar distance, gives the change by pre- 

 cession in that time. Hence, the annual luni-solar precession for 

 each of these Stars is obtained. The near agreement of these re- 

 sults for each Star as exhibited in the Table hereafter given, will 

 shew the degree of confidence that may be placed in them. — The 

 precession separately determined for each Star enables us to deduce 

 the proper motion of the Pole Star by comparing the observed 

 change of N. P. distance with the computed. The mean of 13 

 results gives the proper motion of the Pole Star in declination 

 = 3",2. The near agreement of the quantity of proper motion of 

 the Pole Star in N. P. distance in 66 years, as determined by these 

 difFererit processes, appears to establish the accuracy of the result. 



The proper motion in N. P. distance being taken = + 3",3, the 

 luni-solar precession in Longitude in I788 = 50', 50. This quantity 

 considerably exceeds that determined by Mr. Bessel, but the steps by 

 which it lias been deduced appear to me to render it certain that it 

 cannot be in error more than ^V of a second. This increase of the 

 luni-solar precession will not affect the quantity of general preces- 

 sion, which will be 50",22 nearly as before, but the direct motion of 

 the ecliptic on the equator will be greatly increased, so much so as, 

 according to our present knowledge, to appear incompatible with 

 the result deduced by Physical Astronomy. The accuracy of the 

 general precession aa deduced from observation, depending on the 



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