250 Ocean Magnetic Observations, 1905-16 



Specimen Determinations of Intensity Constants of Sea Dip-Circle 

 Station: A and B, Suva Vou, Fiji Instrument: Sea dip-circle 189 ObsW: H. 



D. F. 



'From simultaneous inclination-observations, made with earth inductor 2 at station B on June 17 and 18. and at station 

 A on June 19; after reduction to C. I. W. Standard, the values were referred to the dip-circle station by means of the station- 

 difference (A - B) = - O'.l. 



''There were no simultaneous observations for H. The adopted value is the mean of 20 with standardized magnetom- 

 et«ra 2 and 4, made at various times from 10^9 to 15^5 on June 11-14, 1912, and referred to the dip-circle stations. 



Sea Dip-Circle Corrections. 



The adopted inclination-corrections and intensity-constants are given below for each 

 sea dip-circle. All corrections and constants are on the basis of C. I. W. Standards (see 

 p. 232). For the regular dip-needles, the incUnation corrections apply to complete deter- 

 minations by both polarities, and for the deflected needle, to the mean of determinations 

 made in both "direct" and "reversed" positions. All inclination values are referred to 

 north-seeking end of needle, inclination of north-seeking end of needle below horizon being 

 reckoned positive. All values of total intensity and horizontal intensity are reckoned positive; 

 values of vertical intensity are given the same sign as the corresponding inclinations. AI and F 

 in the formulae are always expressed in minutes of arc and in c. g. s. units, respectively. 



Sea dip-circle 189. — Sea dip-circle 189, manufactured by Dover, is of the latest pattern 

 (see p. 195). It was used on Cruises I, II, III, and IV, except for March 1915. For 

 Cruise I the adopted inclination-corrections are from a graphical adjustment of observed 

 data at shore stations and of the data derived from the special experimental work at 

 Washington. For Cruise II the adopted inclination-corrections are the means of values of 

 A7i and A72, derived by different methods: (1) by a least-square adjustment of all avail- 

 able data for each needle in accordance with the formula 



FAIi = X -t- 2 cos / -h 2/ sin 7 



and (2) by a time interpolation between the observed corrections at the next preceding and next 

 following stations ; the adopted correction. A/ = ^ {AIi + A/2) . For Cruise III the adopted 

 corrections are the means of the values determined at the 4 shore stations where the sea 

 instruments were compared with the standard instruments for control during this cruise. 



