ASTRONOMY. 20? 



ing node. The inequality thus produced in the 

 precession of the equinoxes, and in the obliqui- 

 ty of the ecliptic, will exactly agree with the 

 appearances as observed. 



It was by this construction, that Dr BRADLEY repre- 

 sented the irregularities he had observed. 



From the oscillatory motion thus ascribed to the pole 

 of the equator, or to the axis of the Earth, the 

 name of nutation is derived. 



219. If N be the longitude of the moon's as- 

 cending node, + 9". 6 cos N is the variation in 

 the obliquity of the ecliptic produced by the nu- 

 tation, and IT' .94*6 sin N is the variation in 

 the precession, or in the equinoctial points. 



The last of these equations affects the longitude of 

 all the heavenly bodies equally. 



DE LAMBRE, Abrege d'Ast. legon 20. 16. 



220. If A be the right ascension of a star, 

 and D its declination, the nutation in right as- 

 cension is 



tan (D 8".373 cos (A N) 1".227 cos (A + N)) ; 

 and the nutation in declination is 



+ 8".373 sin (A N) + 1".227 sin (A + N). 



The 



