16 OUTLINES OF NATURAL PHILOSOPHY. 



and sin 



/. 



1 _ / 



2 ~~ > 



sin /' X sin a' 



By the first formula, the hour can always be deter- 

 mined from astronomical observations, if the time 

 of the star's passing the meridian be known. 



The second formula serves to find the meridian, from 

 the observation of the altitude of a known star. 

 The meridian, however, is better found by obser- 

 ving a star when it has the same altitude on the 

 east and west sides of the meridian, and bisecting 

 the difference of the azimuths, as in 15. 



24. Let a, h and / be given, to find d ; thai is, 

 the altitude, the horary angle, and the latitude* 

 to find the declination. 



a. Here two sides of the triangle ZPS are given, and 

 the angle opposite to one of them, to find the third 

 side. This falls under Case 7. of oblique-angled 

 spherical triangles. 



b. Find 



