386 



MAGNETIC METHOD 



[Chap. 8 



depends on the inverse first power of the distance. In practice this makes 

 surprisingly little difference. 



For magnetic plates of great depth extent, only the magnetized line at 

 the upper end need be considered. If the strike of the line is in the y' 



Fig. 8-476. Anomalies of dipping magnet of 20° dip (after Nippoldt). 



Fig. 8-47c. Anomalies of dipping magnet of 50° dip (after Nippoldt). 

 direction (Fig. 8-48), AY in eq. (8-52a) is zero; AH = -C j ^ , and 



AZ = C I -^^ . Integrating between the limits of 

 J r^'d 



±00, 



AH = 



-2Cx' 



and 



AZ = 



2Cd 



(8-55) 



"See also A. Banos, Revist. Industrial, 1(3), 303-310 (Sept., 1933). 



