MAGNETIC OBSERVATIONS. 



193 



Coefficients of the Deviations of the Forward Binnacle Compass. 



Hampton Roads 

 St. Thomas 

 Bahia . 

 Monte Video 

 Sandy Point 

 Valparaiso . 

 Callao . 

 Panama. 

 Acapulco . 

 San Francisco 



November 



November 



December 



January 



February 



April 



April 



May 

 June 

 June 



l, 1S65 

 iS, 1865 

 30, 1865 

 24, 1S66 

 io, 1866 



4, 1S66 

 29, 1S66 

 20, 1S66 



1, 1866 

 23, 1S66 



XH 



0.000 

 0.000 

 0.000 

 0.000 

 0.000 

 0.000 

 0.000 

 0.000 

 0.000 

 0.000 



^ 



— 0.099 



— 0.034 

 4- 0.008 

 4- 0.051 

 4- 0.092 

 4- 0.031 

 4- 0.020 



— 0.018 



— 0.036 



— 0.082 



G 



• 0.045 



■ 0.004 



■ 0.010 



■ 0.012 

 0.038 



■ 0013 



■ 0.037 



• 0.027 



• 0.029 



■ 0.062 



© 



4- 0.044 

 4- 0.035 

 4- 0.037 

 4 0.032 

 + 0.039 

 4- 0.028 

 4- 0.037 

 4- 0.037 

 4- 0.046 

 4- 0.035 



4- 0.037 



(2 



4- 0.007 



— 0.002 



— 0.003 



— O.OOI 



— 0.004 



— 0.003 

 4- 0.006 



— 0.006 



4- 0.004 

 4- 0.014 



4- O.OOI 



Coefficients of the Deviations of the Forward Ritchie Compass. 



STATION. 



DATE. 



3( 



33 



e 



© 



e 



Hampton Roads . 



November I , 



1865 



0.000 



4- 0.023 



— 0.063 



4- 0.038 . 



-(- 0.006 



St. Thomas 









November IS, 



1865 



0.000 



4- 0.036 



— 0.022 



4- 0.057 



— 0.00S 



Bahia . . 











December 30, 



1865 



0.000 



4- 0.061 



— 0.027 



4- 0.047 



— 0.002 



Monte Video 











January 24, 



1866 



0.000 



4- 0.066 



0.000 



4- 0.040 



— 0.008 



Sandy Point 











February 10, 



iSin, 



0.000 



+ 0.067 



— 0.048 



4- 0.039 



— 0.006 



Valparaiso . 











April 4, 



1866 



0.000 



4- 0023 



— 0.026 



4- 0.037 



4- 0.008 



Callao . 











April 2Q, 



1 86b 



0.000 



4- 0.033 



— 0.034 



4- 0.044 



4- 0.002 



Panama . 











May 20, 



1866 



0.000 



4- 0.004 



—0.033 



4- 0.038 



— 0.004 



Acapulco . 











June I, 



1 866 



0.000 



4- O.OII 



— 0.038 



4- 0.041 



4- 0.007 



San Francisco 











June 23, 



1866 



0.000 



— 0.005 



_ 0.117 



4- 0.025 



■ — 0.009 







M< 



an 





4- 0.041 



O.OOI 



The values of the coefficients © and G for any compass should be constant. 

 Therefore the mean of all the observed values has been assumed as the truth, and is 

 given on the line marked "means" in the case of each compass. 



The constants thus far determined furnish the data with which to compute the 

 values of the coefficients % 33, (J, £>, Q, in any part of the world, for any of the 

 compasses under discussion. For convenience of reference these constants are 

 collected in the following table: 



Compass. 



A 1= 2l 



X 



r 



X 



p 



X 



/ 



X 



e 



X 





X 



© 



a 



Admiralty Standard . 



o.ooo 



+ 



0.0240 



4- 0.460 



— 0.00102 





0.0016 



4- 



0.006 







0.00023 



4-0.017 



O.OOI 



After Binnacle . . . 



— O.OIO 





0.0048 



4- 0.664 



O.OOII2 



— 



0.00S4 



+ 



0.002 



— 



0.00022 



4- 0.038 



— 0.002 



After Ritchie . 



O.OOO 



4 



0.0178 



4- 0.766 



— O.OOI22 



+ 



0.0052 



— 



0.149 



4- 



0.00042 



4 0.034 



O.OOI 



After Azimuth . . . 



0.000 





0.0026 



— 0.373 



— 0.00032 



4 



0.0066 



— 



0.044 14 



0.00039 



4- O.I 12 



0.000 



Forward Alidade . 



— 0.025 



— . 



0.0162 



4- 0.014 



O.OOOIO 



— 



0.0012 



— 



0. 1 ob — 



0. 0003 1 



4- 0.024 



0.000 



Forward Binnacle . 



0.000 



— 



0.0477 



4- 0.140 



— 0.00041 



— 



0.0059 



— 



0.075 — 



0.00074 



4 0037 



4- O.OOI 



Forward Ritchie . 



0.000 



— 



0.0169 



4- 0.367 



— 0.00102 



— 



0.0141 



— 



0.083 



— 



0.. 00 1 20 



4. 0.041 



O.OOI 



The values of the coefficients 2(, 33, G, S), G, for each compass at each station, 

 were next computed from the quantities given in this table, in the following man- 

 ner. The coefficients 21, £), and G are constant for each compass, and were taken 



25 December, 1872. 



