92 



Ocean Magnetic Observations, 1905-16. 



Table 37. — Computation of Declination-Deviations for Standard-Compass (R3C) Position on April I4, 1908. 



Formula: SD = Aa+Bi sin f+C^ cos f +0^ sin 2^+Ei, cos 2f 

 From Table 30 (p. 87): Aa=-°03; Da= + nO; Et=°.00; i=-?1123; y=+°0l32; x'=+?0563; i/'=-?0713. 



Table 38. — Computation of Inclination-Deviations for Sea-Dip-Circle Position on April 14, 1903. 



Formula: SI==A(+B( cos f+Cj sin {•+!>« cos 2 f+^i sin 2f 



From Table 31 (p. 87) : x=+?166; y = +?149; z= +?066; x'= +?390; ?/'= +?020; z'= +?014; i" = -?100; -x"'= -?014. 



For computing Ai from (32), (\— A:-l)/2 sin 1°= +0°196, and fl/sin 1°= -0?055 for all 3 cruises. 



The computation assumes an approximate value of / of — 0?3, which, when the devia- 

 tion-correction, +0°2, is apphed, becomes — 0?1. A recomputation with this new value 

 of I would not, however, make any material difference in the value of the deviation. 



Horizontal Intensity. — The tabular arrangement adopted for the computation of the 

 horizontal-intensity deviations is exempUfied by the calculation of the value for AprU 14, 

 1908, at the sea-deflector position. H = 3280 approximately, in units of fourth decimal 

 c. G. s.; 7 = — 0?3 approximately; course, W, hence, f = 270°. The resulting deviation- 

 correction is -|-22 units in the fourth decimal c. g. s. 



Table 39. — Computation of the Horizontal-Intensity Deviations for Sea-Deflector Position on April I4, 1908. 



Formula: iH=A^+B,, cos f +C;> sin f +Ds cos 2f +£» sin 2f 

 FrombottomUneof Table32(p. 88): P-10*=-4; 0-10'=-4; c= +.00043; /= -.00017; 



i'= +.00450; x"= +.00102. 



Values of H, A),, B/,, C/,, D/,, E/,, and the deviation are in units of the 4th decimal c. g. s. 



tan / 



-.005 



ff tan/ 



-16 



cH tan / 



/Htan/ 



Cft 



+4 



D^ 



+ 15 



E^ 



-3 



B» cos f 



C^sinf 



Dft cos 2f 



-15 



£;Asin2f 



Devia- 

 tion 



-22 



The horizontal-intensity deviations for the dip-circle position were obtained on a form 

 similar to that shown in Table 39. 



