66 



Ocean Magnetic Observations, 1905-16 

 Sea Dip-Circle Corrections. 



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

 sea dip-circle. All corrections, unless otherwise noted, are on the basis of C. I. W stand- 

 ards The inclination corrections for the dip needles apply to complete dip deterniina- 

 tions by both polarities, and for the deflected needle to dip determinations made in both 

 'Xect^ and "reversed" positions. For the sea observations, when the dip was observed 

 Xonly one polarity of needle, the correction to obtain the mean value for both polarities 

 is taken from the table of "half polarity-differences." Thus (see p. 64), either 



I = lB + ^ilA-lB), or I = I^-\{Ia-Ib). 



All inclination values are referred to north-seeking end of needle, inclinat^n of north-seeking 

 end of needle below the horizon being reckoned posUive. All values of total ^nens^ty andhon- 

 zontal intensity are reckoned positive; values of the vertical intenstty are given the same signs as 

 the corresponding inclinations. •. „.,„ri^ u is fnl 



Whenever a listed needle is not a part of the circle to which reference is made it ^ f ol- 

 lowed^by the number of the circle to which it belongs; thus, 5 of 163 means needle No. 5 

 of dip ch-cle No. 163. The quantities A/ and F in the formula are always expressed, 

 resDectivelv, in minutes of arc and in c. g. s. units. xi tt -j. j a+„+^o 



Sea ^p.ci.cle 35.-8e^ dip-circle 35 (Dover No. 168), loaned by «?« United States 

 Coast and Geodetic Survey, was used for some expermiental work P''^^?^ f Q^^,f J^J^; 

 after being reconstructed (see p. 21), for observations on board the Galilee durmg Lruises 

 II and in (to Suly 1907). The dip and intensity needles for this instrument are listed m 

 the inventory of instruments (see pp. 30-31). , 



The adopted formute resulting from least-square adjustments of all available data 

 for corrections to observed inclinations are given m Table 10. 



Table W.— Inclination Corrections for Sea Dip-Circle 35. 



•Needles 4 of circle 35 and 169 were used for short periods only (see footnotes. Table 12) . 

 AvaUable data are insufficient for showing variation of AZ with f and 1. 



