308 OUTLINES OF NATURAL PHILOSOPHY. 



SECT. Vll. 



OF THE PRECESSION OF EQUINOXES. 



311. THE precession of the equinoxes, is the 

 slow angular motion by which the intersection 

 of the equator and ecliptic goes backward, at 

 the rate of 50 r/ | annually ; while the inclina- 

 tion of these planes continues nearly the same ; 

 so that the pole of the equator describes a cir- 

 cle about the pole of the ecliptic in the space of 

 257^8 years nearly. 



In seeking for the cause of this phenomenon, it is 

 natural to inquire how the gravitation toward dis- 

 tant bodies, such as the Sun and Moon, may af- 

 fect the Earth's rotation on its axis. 



312. From what has been proved of the force 

 with which the Sun disturbs the motion of the 

 Moon, it is evident, that every particle in that 

 hemisphere of the Earth which is turned to- 

 ward the Sun, is drawn toward that body, while 

 every particle in the other hemisphere is drawn 

 in the opposite direction, the force that acts 



on 



