40 



Mr. Gr. Barlow. Effects of Magnetisation [June 18, 



resistance change. The nickel coil was subjected to the demagnetising 

 process before each reading. 



The variation of resistance is shown in fig. 7. 



Fig. 7. 



£0,000 



In weak fields, A</> has a small positive value, but a reversal takes 

 place in a field of 1500 c.g.s. For higher fields A<£ is negative and 

 increases continuously ; even in the highest field, H = 28,000, there is 

 no indication of A<f> having a definite limit. The general form of the 

 curve is similar to the curves obtained by Beattie for certain nickel 

 films. 



From these results it was found that the decrease observed in 

 Experiment II might be accounted for by assuming that about one- 

 fifth of the wire was transversely magnetised. The slight decrease 

 observed in Experiment I is also to be explained in the same way. 



Experiment IV. — Transverse Effect in Nickel. 



A flat spiral of the nickel wire was inclosed between two plates of 

 mica. Using the fine pole pieces at a distance apart of only 1 mm,, 

 the following result was obtained : — 



Ad> = -0-0199, H = 34,000 c.g.s. 



The field strength was determined before placing the spiral in the 

 field. This value of the resistance change is the greatest effect ob- 

 served in these experiments. 



