Ship Deviation-Coefficients 



91 



Deviation-Constants for Chief Vessels Engaged in Ocean Magnetic Work. 



Table 36 gives for the chief vessels which have been engaged in ocean magnetic work 

 the 12 fundamental deviation-constants (or combinations of them) that represent the 

 induced and permanent magnetic forces aboard ship. The data for the first four vessels 

 have been taken from Bidlingmaier's article, page 486 of the 1905 edition of Neumayer's 

 " Anleitungen^ " ; sm. in the table means a small value. The data for the Discovery, 1904, 

 are taken from pages 148-149 of the volume on "Physical Observations of the National 

 Antarctic Expedition, 1901-1904." A'^ and E'^ were assumed to be zero.^ 



It will be noticed that for the Galilee, at each instrument-position, the constants are, 

 in general, smaller than those for previous vessels. Furthermore, the deviation-corrections 

 for two different instrument-positions, e.g., as used in getting H, are of varying amount 

 and even of different sign, so that the resultant mean effects, as shown in the last column, 

 are very small. The values in Table 36 are the means of the 3 cruises, giving each cruise 

 equal weight. 



Table 36. — Deviaiion-Conslants for the Chief Vessels which have been engaged in Ocean Magnetic Work. 



[All quantities are expressed in units of the third decimal except X. P, Q, R are expressed in 

 units of the third decimal c. o. s.] 



SPECIMEN COMPUTATIONS OF DEVIATION-CORRECTIONS. 



As specimens, the deviation-corrections will be computed for April 14, 1908, the day 

 on which the specimen observations, given on pages 46-53, were made. This day falls in 

 group 6 of Cruise III (Callao to San Francisco). 



Declination. — For the morning observations we have the approximate values /^ = 0.328 

 c. G. s., and/ = - 0?2; for the afternoon observations, H = 0.330, and I = -\- 0?1. The 

 course for both a. m. and p. m. was WSW; hence, f = 247?5. The deviation-correction, 

 applied to both a. m. and p. m. decUnations (see Table 37, p. 92), is -0°.08. 



Inclination.— H = 0.330 c. g. s. approximately; / = - 0°.3 approximately; course, 

 W; hence, f = 270°. 



'See reference in footnote, p. 78. . i. . ■ j u 



'The followint' two departures from the generally accepted notation occur m the Discovery publication, viz, d has 

 the meaning usually assigned to k, and V that usually assigned to R. 



K y j .. 



