AZIMUTH IN TRIGONOMETRICAL OPERATIONS. 



99 



These formulae, computed similarly to the former examples, will stand 

 as follow. Suppose that (instead of }° 36'j the polar distance had been 

 1° 35' 34", but that all the observations had been already computed with 

 the former of these values. Then we shall have d 5 — — 26". 



(16 = — 26" Log 1,41497 Log 1.41497 Log 1.41497 



6= 1° 3G' 0" Sec 0.00017 Tan 2.44611 



^ ^. _ o j = 24° 0' 36" Tan 1.64878 Tan 1.64878 



15A. C. Log 2.82391 



A = Cosec 0.00003 



X = Sec 0.03927 









Corrections, 0.77 . 



.Log 1.88783 28".46. . 



Log 1.45427. .0".32. .Log 1.50986 



1st. Compd. values,. 16 16 13.84 



1° 45' 5 .37 . 



24 2.45.66 



Correct values, 16 16 14.61. 



1° 44' 36.91" 



24 2.45.34 



In these computations, the correction is applied to the altitude with 

 an opposite sign to that resulting from the formulae, as due to the 

 zenith distance, the rationale of which will be evident. The formulae will 

 evidently shorten such operations considerably, because there is no 

 necessity for more than five places of decimals, unless the variations are 

 very large, and thus, if we retain all the quantities but the variation 

 of b, we may compute a set of observations for many nights in succession, 

 by merely finding the variations which are occasioned in the other parts. 



In the work on the great Meridional Arc of India, which the Court 

 of Directors did me the honor to have printed, the principle is examined 

 (vide page 89,) of determining for how long periods some of the principal 

 circumpolar stars of the Greenwich Catalogue may be considered as 

 stationary in Azimmh ; and it is therein shewn that, during the 2' 3/6 

 preceding and subsecpient to the IMaxinunn. llic vai iai ion in Azimuth of 

 the Pole Star is only 0/2o, a ([uantity less than tlio powers of our best 

 instruments can be considered capable of detecting under ordinary 



