Chap. 8] 



MAGNETIC METHOD 



385 



Anomalies for inclined magnets 

 are shown in Fig. 8-47, a to d. The 

 AZ curves are unsymmetrical ; in 

 the AH curves the ratio of maxi- 

 mum to minimum increases with 

 decreasing dip. Dip determina- 

 tions may be made (a) indirectly, 

 by using diagrams as shown in 

 Fig. 8-47 or force-line diagrams; 

 or (6) directly (for small intervals 

 of dip angle) from the ratio of 

 maximum to minimum in AH. 

 For the range of 30° to 60", 

 At is approximately equal to 



3AH min./AH max. 



4. Magnetized lines are assumed in the interpretation of the magnetic 

 anomahes of two-dimensional bodies whose extent may be considered 

 infinite in the direction of strike. These bodies include most stratified 

 magnetic formations, iron and nickel ore deposits, intrusive dikes, contact- 

 metamorphic zones, and the like. While the magnetic field of a three- 

 dimensional body is inversely proportional to the square of the distance 

 between it and the point of observation, the field of a two-dimensional body 



Fig. 8-46. Dipping magnet. 



Fig. 8-47a. Anomalies of dipping magnet of 0? dip (after Nippoldt). 



