300 Ocafltatlo??s of stars at Madras. [July 



Now 1st instant . . +t^-f or — according to the sign of 

 the hour angle)— time of apparent conjunction in right 



ascension. Eut in the interval t, the Moon's declina- 

 tion will he altered by (d + P — P') t. 

 Therefore 



A + P^ -I- f-P' — py—apparentdifFerence of declin- 

 ations at apparent conjunction in ris;ht ascension. 



Let us now suppose the Moon to be stationary and the 

 star to be relatively in motion. 



Let N. w. y represent the Moon's surface; c the cen- 

 tre ; a b and b e the star's apparent horary motion in 

 right ascension and declination ; a e the portion of the 

 orbit described in one hour ; c x the difference of appa- 

 rent declinations at apparent in right ascension, and 

 c n the nearest approach of the centres. 



Now c n X and x d a being right angles, 

 the angle d a x=90 — d x a. 



=.90— c X n. 

 :=90— (90— X c n). 

 =x c n. 



