LONGITUDE. 



In this example the log. difF., taken from Mackay's Table XLIL is fubflituted for the following logarithms, which are 

 ufed by the author, and arc indeed common to all the formulae of this nature. 



Log. fecant of apparent altitude ... 0.0743564 



Log. fecant of apparent altitude ]) ... 0.1098114 



Log. cofine of true altitude - - - - 9-925'7539 



Log. cofine of true altitude p - - - - 9.8S55952 \ 



Sum . . - 9.9955169 



This fum is the referved logarithm of Requifite Tables, and that of Table XLII. ef Mackay. 



Apparent altitude O 

 Correction R — P 

 O's true altitude 

 Apparent altitude P 

 Horizontal parallax 

 Parallax of J) in altitude 

 Refraction 



Correftion of J) 's altitude 

 J 's true altitude 



Apparent diftance G B 

 Apparent altitude © 

 Apparent altitude J 



Sum 



Half fum 



Diftance — \ fum 



True altitude 



True altitude B - - 



Sum of true altitudes 



Another Example by Borda's method. 

 42 3' 20" 

 - 56 

 42 2 24 



26 lo 15 



56 3'-5 

 + 50 43-5 

 - I 55 



+ 48 48-5 

 26 52 3.5 



Log. cofine 0.9530262 

 Log. fine 8.2159471 



8.1689733 



Half fum 



Half true diftance 



True diftance 



69 I 27.5 



34 3° 43-7 



49 43 52 

 2 



99 27 44 



Sum 2)38.9888247 



Half fum 

 Log. cof. A f 

 Log. cof. N \ 



Log. fin. 



19.4929123 j 



9-9I59307 i 

 9.9666044 



DifF. = 9.57698 1 6 fin. < N 



9.8825351 



Same 



