Chap. 



MAGNETIC METHOD 



337 



tions incorporating the original Z are made at the same station. The 

 diagram shown in Fig. 8-25 represents the vertical intensity correction as 

 a function of readings from 20 and difference in vertical intensity. 



As in the vertical magnetometer, the effect of gravity variations is negli- 

 gible. The influence of temperature may be described in the same manner 

 as for the vertical magnetometer (eq's. [8-25]). Employing the notation 



fSff 

 80 

 60 

 40 

 10 



/IZ inr 



3600^-^J8 



Fig. 8-25. Effect of vertical intensity changes on horizontal magnetometer. 



in these equations, the following formula is obtained for the combined 

 magnetic and mechanical effects of temperature: 



^ Of r^H(l - M.e) - mga{\ - p9) "| 

 U 



*® ^' ' MZ(1 - M«e) - mgd{\ - qe)J' 

 For a compensated system, 



— /Xs = p 



and 



q = 



mgd 



(8-33) 



(8-34) 



conditions which are effected in the earlier magnetic systems by shifting 

 the blades and in the newer systems by suitable spindle adjustment. The 

 effect of temperature on auxiliary magnets is the same as in the vertical 



