§1$ Mr. S. Beswick on a Method/or 



(12.) sine 16° 2' .... 944122 



sine 24° 24' ... . 961906 



1905728 

 sine 24° 41' ... . 962076 



sine 15° 51' . . . . 943652 

 which is the southern angle. 



(13.) Having obtained the two sides and angles required 

 by the theory of Gauss, we now proceed to find the value of 

 the angle bcx formed by the needle. As the sum of the sides 

 bc + cg (43° 54' -1-155° 19'=199° 13') is to the sum of the 

 angles or bca+gch{33° 26'+ 15° 5l' = 49° 17'), so is the north 

 side 6c (43° 54') to the angle bcs {10° 51'). Or more clearly 

 thus : 



Sides. Angles. 



43° 54' 33° 26' 



155° 19' 15° 51' 



199° 13' : 49° 17' : : 43° 54' : 10° 51' 



Hence if bcx be subtracted from bca, there will remain the 

 angle xca which the needle makes with the meridian of Green- 

 wich, in other words the declination. 



33° 26' 

 10° 51' 



22° 35' W. 



which is the mean west declination at Greenwich for the pre- 

 sent year 1849. 



Mr. James Glaisher, of the Royal Observatory, informed 

 me, June 27, 1849, "that the average value of the W. declina- 

 tion at Greenvoichy at present, is about 22° 35'." 



Calculation of the Mean Declination at St. Helena for the 

 present year 1849. 



(1.) S. lat. 15° 55' : comp. 74° 5'. 



W. long. 5° 43'. 



(2.) Lat. and long, of N. magnetic pole. 

 N. lat. 70° : comp. 20°. 



(3.) 



