MAGNETIC OBSERVATIONS. 



191 



Forward Ritchie Compass. 

 Equations of Condition. 



Absolute Terms. 



A x 



c 



p 



a/' 



/ 



Q 



AC 







. \ 



\ 



\ 



A 



\ 



X 



o = — 0.023 



— 0.063 



+ 2-694 



+ 0.212 











= — 0.036 



— 0.022 



+ 1-176 



+ 0.148 



+ 2.520 









= — 061 



— 0.027 



+ 0.077 



4- 0.161 



+ 9-5'6 









= — 0.066 



0.000 



— 0.603 



4- 0.166 



+ '3-933 









= — 0.067 



— 0.048 



— 1.426 



4- 0.164 



4- 16.522 









= — 0.023 



— 0.026 



— 0.710 



+ 0.158 



+ 24-375 









= — 0.033 



— 0.034 



— 0.1 13 



+ 0.143 ' 



+ 25.C0S 









= — 0. 004 



— °°33 



4- 0-623 



+ 0.132 



+ 26.316 









O = — O.OI I 



— 0.038 



+ 0.836 



4-0.129 



+ 27.440 









= 4- 0.005 



— 0. 117 



+ 1. 910 



+ 0.177 



+ 4ISI9 









= 4- 0.063 



— 0023 









+ 2.694 



+ 0.212 





= + 0.022 



— 0.036 









+ 1176 



+ 0.14S 



+ 2.5*) 





— 0.061 









+ 0.077 



+ 0.161 



+ 9-5'6 



= -f 0.04S 



— 0.066 



— 0.067 









— 0.603 



— 1.426 



+ 0.166 

 + 0.164 



+ "3-933 



4- 10.522 



= -j- 0.034 



— 0.023 









— 0.710 



+ 0.158 



+ 24-375 



— oo33 









— 0.1 13 



+ 0.143 



4- 25.608 



— 1- 0.033 



— 0.004 









+ 0.623 



+ 0.132 



+ 26.316 





— o.ou 









+ O.S36 



-f 0.129 



+ 27-440 





-(- 0.005 









+ i-9'o 1 



+ 0.177 



+ 4'-5>9 



o = 0.000 

 o = 4- 0.044 

 o = — 0.052 

 o = — 4.306 

 o = + 0.384 

 o = + 0.068 



O = + 9-388 



Hence 



Normal Equations. 



+ 0.042 



— 0.384 



— 0.06S 



— 9.3SS 

 + 0.044 



— 0.052 



— 4.306 



+ 16.294 

 + 0.826 

 + 70.177 



+ 0.258 

 4- 2S.S25 



+ 49S3-3 



A i = 0.000 



c , 



- = — 0.0169 



= + 0.367 



=1 — 0.00102 



4- 16.294 



4- 0.S26 I 4- 0.258 



+ 70.177 I +2S.S25 



— = — 0.0141 



= — 0.0S3 



AC 



+ 49S3-3 



: O.OOI20 



The value of the true A x having thus become known for each compass, the 

 values of the coefficients 33, @, §>, and (£, for each compass, at each station, wore 

 next computed by means of the formula? (16). The results, expressed in parts of 

 radius, are as follows: 



Coefficients of the Deviations of the Admiralty Standard Compass. 



STATION. 



DATE. 



% 



53 



s 



© 



G 



Hampton Roads . 



November 



I, 



1865 



0.000 



+ 0.1 5 s 



O.OIO 



4- 0.021 



— 0.004 



St. Thomas 









November 



18, 



1S65 



0.000 



4- 0. 100 



4- O.OIO 



4- 0.006 



— 0.013 



Bahia . . 











December 



^o, 



1865 



0.000 



+ 0.064 



0.000 



4- 0.016 



0.000 



Monte Video 











January 



24. 



1866 



0.000 



+ 0.054 



4- 0.002 



4- 0.024 



4- 0.004 



Sandy Point 











February 



10, 



1 866 



0.000 



+ 0.025 



— O.OI2 



4- 0.016 



0.000 



Valparaiso . 











April 



4. 



1866 



0.000 



+ 0.023 



— 0.002 



4- 0.016 



— 0.003 



Callao . 











April 



29. 



1866 



.0.000 



4- 0.041 



0.000 



4- 0.016 



4- 0.002 



Panama . 











May 



20. 



1866 



0.000 



+ 0.053 



4- O.OOI 



4-0.017 



4- 0.002 



Acapulco . 











June 



1, 



1866 



0.000 



+ 0.048 



4- 0.002 



4- 0.018 



4- 0.002 



San Francisco 











June 



23, 



1866 



0.000 



+ 0.0S5 



— 0.022 



4- 0.018 



0.000 







Me 



an 





4- 0.017 



— O.OOI 



