OUTLINES OF NATURAL PHILOSOPHY. 



and the arc AS, in the triangle ABS. Hence 

 the angle SAD being known, and the side AS, 

 in the triangle ADS, the sides AD and DS are 

 found. This is somewhat more prolix. CAGNOLI, 

 1448, (2d, edit.) considers the subject different- 

 ly, but brings out the same solution with Dr MAS- 



KELYNE. 



DE LAMBRE has computed tables, for faciliating 

 this computation, as it occurs very often in as- 

 tronomy. 



If the star is in the ecliptic, or Lat. = 0, x = <p, 

 andj/ = 0, therefore cosy = 1, and 



T tan Right Asc. 



tan Long. = - 



cos<p 



The changes are obvious, that would make the same 

 formulas apply to the converse of the problem, 

 viz. to find the right ascension and declination 

 from the longitude and latitude being given. 



31. By the methods now explained, and 

 chiefly by the observations made on the meri- 

 dian, catalogues of the stars have been formed, 

 in which their places are all set down in res- 

 pect of the circles of the sphere, viz. the Eclip- 

 tic or the Equator, but most commonly the for- 

 mer. 



a. HIPPARCHUS began the first catalogue of the fix- 

 ed stars, 120 years A. C. " Ausus," says PLINY, 



rein 



