Hackktt — The Tivist and Magnetisation of a Steel Tube. 423 



to 1 per cent. In fact, this maximum can be used to determine the equivalent 

 position of the poles, assuming that the change of intensity of the magnetic 

 field at the magnetometer near the maximum is due to poles localized at two 

 points symmetrically placed with reference to the ends of the bar. The 

 position of these equivalent poles was thus found to be 4'0 cm. from the ends, 

 and the distance between them 87*1 cm. 



-1000 



— 800 



— 600 



— 400 £ 



— 200 



4. 6 



Anhysteretic spiral magnetization. 

 Fig. 3. 



Anhysteretic spiral magnetization. — As the intensity of magnetization 

 measured is only the longitudinal component Ii a of the total intensity I s ' in 

 applied spiral field 8' with pitch-angle a, we should expect to find 



Iu = Is' sin a, 



if the following assumptions hold:— (1) That the applied spiral field (a) gives 

 a magnetization parallel to its own direction; (b) produces exactly the same 



SCIENT. PROC. R.D.S,, VOL. XV., NO, XXXIII. 3 Y 



