382 MAGNETIC METHOD [Chap. 8 



Assuming uniform magnetization, the pole strength m = ,^S, where S 

 is the section of the body and d is intensity of magnetization. For a 

 vertical body, B = kZo , so that 



m = /cZoS. (8-52b) 



This relation presupposes that the magnetization is due exclusively to 

 induction. Where an appreciable remanent magnetization exists, the pole 

 strength resulting therefrom is usually greater than that due to induction 

 so that the latter may be neglected, in which case 



m = ^rS, (8-52c) 



where Br is the remanent magnetization. For example, the magnetization 

 intensity resulting from the remanent magnetism of the diabase in Fig. 

 8-13 is 0.17, whereas the induced magnetization B = kZo is only 5 -10" . 

 This subject is discussed further on pages 400-402. 



The vertical intensity reaches a maximum when r = d; AZ^ax. = m/d • 

 If the variable parameter q = d/r — sin i is introduced, 



AZ = q' 5 and AH = q' ^ ^\ _ i. (8-52d) 



For the single pole, horizontal and vertical intensities at any point are 

 functions of the vertical intensity directly above the pole: 



AZ = AZ„a^.q' and AH = AZ^^ax.q^ \/l - q' • (8-52€) 



Figure 8-45 shows the horizontal and vertical intensity anomalies as 

 profile curves and isanomalic lines. The horizontal intensity is zero above 

 the pole and has a minimum in the north (positive x) and a maximum in 

 the south (negative re). In horizontal projection, the lines of force for a 

 single pole are straight. 



From the above formulas follow a number of relations which are helpful 

 in interpretation: 



(a) The highest point of the subsurface (polar) mass lies immediately 

 below the maximum in AZ and the zero point in AH. 



(6) The anomalous vectors intersect in the pole. 



(c) The drop of the vertical intensity curve is inversely proportional to 

 the depth of the pole. If ei is the distance at which the vertical intensity 

 has dropped to one-half of its maximum value, d = -|ei , and the distance 

 of the half-value point from the point of maximum anomaly in Z is equal 

 to f the depth of the pole. 



(d) The distance of a point where AZ has dropped to iAZmax. is equal 

 to the depth of the pole. 



(e) The distance of the point where AZ = AH (where the angle of the 



