Reductions to Standard Instruments 



73 



shows that while the coefficients of the formulse might now be somewhat improved, the 

 additional labor involved in carrying out the work necessary for the slight revisions which 

 would result is hardly warranted. As stated on page 96, values for inclination obtained 

 from the deflected-needle observations of the total-intensity work are given less weight than 

 those from the regular dip-needles. It is interesting to note from Table 19 the increasing 

 uncertainty for inclinations obtained from short-distance deflections as the critical condi- 

 tion when deflections fail is approached. To facilitate the computations, graphs were con- 

 structed for the values of FM, computed from the adopted formulse. Specimen graphs 

 for sea dip-circle 169 are shown in Figure 2, values of FM and of the inclination being 

 indicated by ordinates and abscissae respectively; the dash-dot line and the hne of dashes 

 only, signify, respectively, needle direct and reversed. 



■80° 



+ 60 



+ 40' 



+ 20° 



-20° 



■40° 



-SO" 



-80 



+ 1 

 O' 

 -l' 



♦ l' 



o' 



-r 



-2' 



♦ 2' 



♦ I' 

 O' 



+4' 



♦ 3' 

 +2' 



+r 



o' 



Fio. 2. — Curves showing Dip-Needle Correctiong for Sea Dip-Circle 169 during Cruise III. 



Table 20 gives a condensed summary of the observed and computed data for the 

 adopted intensity-constants for needles 7 and 8, the latter loaded with weight 31, for sea 

 dip-circle 169, which was used throughout Cruise III. That table is tj^Dical of the reduc- 

 tions made for each intensity-needle pair for each circle. To facilitate the computations, 

 graphs were constructed for the values of the logarithms of each intensity-constant com- 

 puted from the adopted formulse. Figure 3 shows specimen graphs for sea dip-circle 169. 



