Juis 53 



then he found that s' M was equal to the former s M, 

 but that TM' was greater than. the former TM, or that M' 



M 



FIG. 22. The movement of the equator. 



was slightly to the east of M. This change M M' being 



nearly the same for all stars, it was simpler to attribute it 



to an equal motion in the 



opposite direction of the 



point T , say from T to T ' 



(fig. 22), i.e. by a motion of 



the equator from TN to 



T'N', its inclination N' T'M 



remaining equal to its former 



amount N T M. The general 



effect of this change is shewn 



in a different way in fig. 23, 



where T T' =~ * being the 



ecliptic, A B c D represents 



the equator as it appeared 



in the time of Timocharis, 



A'B'C'D' (printed in red) FIG. 23. The precession of the 



the same in the time of equinoxes. 



Hipparchus, r, === being the 



earlier positions of the two equinoctial points, and r', t 



the later positions. 



