the Magnetic Properties of Iron. 



257 



This is only approximate, since the assumption is here made that the 

 effective distance between the poles is the full length of the sample. 

 Inserting these values in (1) we have 



B 2 = 



1-6 x 6,120 x 491 x 4tt x 7'78 



114 



= 41,250,000, 



B = 6,410, and H = 



6,410 



= 3'06, or 1-09 gauss per div. 



B 



Fig. 7. 

 The length of the sample was 7*62 cms., hence the cross-section 



LI* = -oi 93 



_ 778x7-62 Uiyd ' 



therefore Ba= 6,410 x 0193 = 1233, or 77 per div. of B scale. 



Hence to obtain B in any sample, multiply the B scale read- 

 ing by 77, and divide by the cross-section of the specimen. 



Results Obtained. 



Figs. 6 and 7 shew examples of hysteresis cycles got with the 

 instrument. 



VOL. XIII. pt. v. 



18 



