PRECESSION OF THE EQUINOXES. 313 



From this solution we may date the important improve- 

 ments of the lunar tables effected in the last century. 



The most beautiful astronomical discovery of anti- 

 quity, is that of the precession of the equinoxes. Hip- 

 parchus, to whom the honour of it is due, gave a com- 

 plete and precise statement of all the consequences which 

 flow from this movement. Two of these have more 

 especially attracted attention. 



By reason of the precession of the equinoxes, it is not 

 always the same groups of stars, the same constellations, 

 which are perceived in the heavens at the same season 

 of the year. In the lapse of ages the constellations of 

 winter will become those of summer and reciprocally. 



By reason of the precession of the eqitinoxes, the pole 

 does not always occupy the same place in the starry 

 vault. The moderately bright star which is very justly 

 named in the present day, the pole star, was far removed 

 from the pole in the time of Hipparchus ; in the course 

 of a few centuries it will again appear removed from it. 

 The designation of pole star has been, and will be, ap- 

 plied to stars very distant from each other. 



When the inquirer in attempting to explain natural 

 phenomena has the misfortune to enter upon a wrong 

 path, each precise observation throws him into new com- 

 plications. Seven spheres of crystal did not suffice for 

 representing the phenomena as soon as the illustrious 

 astronomer of Rhodes discovered precession. An eighth 



same time by Euler, D'Alembert, and Clairaut. The two last-men- 

 tioned geometers communicated their solutions to the Academy of 

 Sciences on the same day, November 15, 1747. Euler had already in 

 1746 published tables of the moon, founded on his solution of the same 

 problem, the details of which he subsequently published in 1753. 

 Translator. 



14 



