Brown — Mechanical Stress and Magnetisation of Nickel. 41 



It seems evident, therefore, in both nickel and iron wires, that the con- 

 figuration of the molecules of the materials is suoli tliat the internal molecular 

 friction is the greatest when that longitudinal magnetic field is round the wire 

 which gives the maximum twist for tlie given load. 



240 



200 



180 



E OXIO 



5 10 '^ . 



Fig. 4.— Longitudiual Magnetic Field. 

 With iron wires this magnetic field is independent of the magnitude of the 

 load on the wire, but increases as the diameter of the wire is increased, and for 

 the sizes of wires under discussion it is also the magnetic field in which the 

 maximum transient current was obtained when the wire was mechanically 

 twisted.' "With nickel wire this field increases as the load on the wire is 

 increased, but is independent of the diameter of the wire.^ 



Section 3. — Influence of Amplitude of Oscillation. 

 Experiments were now made in order to find out what influence the 

 magnitude of the initial amplitude of oscillation has on the rates of subsidence 

 of a wire magnetised longitudinally. 



' Scient. Pioe. Roy. Dub. Soc, vol. xii., No. 17, p. ISl. 

 ■Ibid., vol. lii., No. 37, p. 513. 



