ASTRONOMY. 129 



= (6 IS' 17".S) sin x + (12' -49"-7) sin 2 * 

 + (42".3) sin 3 #, ,r being put for the mean ano- 

 maly, reckoned from the perigee. 



This is the equation of the centre, as deduced from 

 DE LAMBRE'S Tables, published in ViNC&'aAstron. 

 vol. in. see p. 133., &c. 



The maximum of the equation is 6 17' 28", and 

 takes place when the mean anomaly = 86 5' 0". 



. The axis of the lunar orbit is not at rest, 

 but has a progressive motion, like that of the 

 sun's orbit. This motion is & 41" in a day, 

 or 40 41' 33" in a year ; so that it makes an en- 

 tire revolution, relatively to the fixed stars, in 

 3232 d .5807, or in a little more than nine years. 



The Tropical revolution of the perigee is shorter by 

 K1056. 



The motions hitherto enumerated, are similar in the 

 Moon and in the Sun. There are other inequa- 

 lities peculiar to the moon. 



129. The moon's longitude, calculated ac- 

 cording to the laws of the elliptic motion, does 

 not agree exactly with her true place, but re- 

 quires to be corrected by an arch proportional 



VOL, JL I to 



