498 MR JAMES RUSSELL ON THE SUPERPOSITION OF MECHANICAL VIBRATIONS 



A and B Conditions. — If the cyclic field be not unduly increased, the curves cross 

 each other under the A conditions when both field and induction are decreasing, but 

 under the B conditions when both field and induction are increasing. They cross the 

 vertical and horizontal axes in inverse order under the two conditions of relative super- 

 position of vibrations and field. Consequently, under the A conditions residual mag- 

 netisation and coercive force are progressively decreased, but under the B conditions 

 progressively increased, with increasing intensity of vibrations. 



Note, however, that if the cyclic field were sufficiently increased the increase of 

 induction at cyclic extremes would nearly vanish, and in all probability the loops would 

 be progressively decreased with vibrations of increasing intensity. In all probability 

 also the curves would cross the vertical and horizontal axes in the same order as they 

 do under the B conditions. 



Experiments, however, were not continued in this direction ; indeed, the vibrations 

 were varied more for the purpose of determining the most suitable intensity to use 

 throughout the experiments now to be described, than for completely investigating the 

 effects of such variations at all stages of magnetisation. 



Intensity of Vibrations, Constant (pages 498 to 508). 



We now pass on to consider the effects of vibrations, not when their intensity is 

 varied, but when the field and consequent magnetisation are varied, the intensity of 

 vibrations remaining the same. The three magnetic metals are all tested in this way, 

 both in the annealed and in the quenched condition. 



The strongest vibrational intensity, corresponding to curves 3 of figs. I. and II., is 

 now used throughout. 



Annealed Metals, B Conditions. 



Permeability and Retentivity Diagrams. — Figs. III., IV., and V. show, for the 

 annealed condition of iron, steel, and nickel respectively, the usual B, H curves obtained 

 in the manner already described, also curves of residual magnetisation (likewise plotted 

 against H) obtained by withdrawing the field at all values of the induction 

 measured. The full and faint continuous lines are the normal induction and the 

 normal residual magnetisation curves respectively without vibrations. The full and 

 faint dotted lines are the induction and residual magnetisation curves respectively 

 with permanently acting vibrations. 



The full and faint dash curves show the ratios B v /B and B v — R v /B — K respectively,, 

 for all values of H. B and R signify the induction and residual magnetisation without 

 vibrations ; B v and R v , the induction and residual magnetisation with vibrations. 



The ordinates and abscissas (H) are drawn to the same scale in the three figs., 

 except that the scale of the ordinates for the permeability and retentivity curves in 

 fig. V. (nickel) have been increased five times. The values of the ratio ordinates 



