On the Quantity of the precession of the Equinoxes, as determined 

 by certain Stars that appear to have no proper motion. By 

 The President. 



Read January 17, 1825. 



The observations of astronomers during the last half century have 

 shewn that a multitude of stars, which had usually been consi- 

 dered fixed, are not really so. They exhibit a regular change of 

 place, very perceptible in the course of a few years ; which, with 

 respect to any one star, arises either from the motion of our own 

 system, or from the motion of the star, or from the combined motion 

 of each system. In different stars the directions of these motions 

 are so various, that little hope can be entertained of developing the 

 motion of our own system, or of ascertaining whether, with respect 

 to any one star, it be at all sensible. 



These apparent motions, although, when contemplated in con- 

 junction with the immeasurable distances of the bodies, they afford 

 us most sublime views of the creation, are in some degree inconve- 

 nient to the astronomer. 



In referring any motions in our system to a fixed star, it was 

 formerly supposed we referred to a permanent point ; now we find 

 it not easy to separate the motion of the star from the motion to 

 be investigated. Thus, in the important matter of the quantity of 

 precession of the equinoxes, it was thought only necessary to com* 

 pare the distances of a star in the ecliptic from the equinoctial 

 point at two distant periods. The motions now ascertained to 

 belong to so many stars render entirely unsafe this mode of proceed- 



VOL. XV. B 



