308 



MAGNETIC METHOD 



[Chap. 8 



Fig. 8-12. Hysteresis curve for Upper 

 Devonian diabase (no magnetite, Harz 

 mountains, 1 amp. = 29.4 gauss). (After 

 Beyer.) 



hysteresis loops obtained by meth- 

 ods previously described. They 

 represent true values (from the 

 physical standpoint) only if the 

 sample has been magnetized to 

 saturation. 



Magnetization to saturation has 

 been applied by Puzicha, Loewin- 

 son-Lessing, and Mitkevitch. 

 Their fields were of the order of 3 

 to 5000 gauss. Samples were sub- 

 jected to hammer blows to insure 

 complete magnetization. Loew- 

 inson-Lessing and Mitkevitch 

 found that specimens whose natu- 

 ral magnetism was due to induc- 



K'W 

 2000- 



1000 -, 



7 



o.e- 



0.5 



J I 



5 10 J5Amp. 02 



oft 



15 



15 Amp. 



Fig. 8-13. Hysteresis and susceptibility curves for Upper Devonian diabase 

 (containing magnetite, Harz mountains, 1 amp. = 29.4 gauss). (After Beyer.) 



