472 Mr. J. Russell on the Superposition of 



H being further increased, maximum values of B v — B occur, 

 so far as observed, a little earlier than maximum values 

 of dB/dH. In annealed steel the maximum value of 

 B v — B = 4500, in annealed iron 2300, in annealed nickel 

 1250, but in quenched iron and steel rather less (700) than 

 in quenched nickel (1000). 



Negative Induction Change. — The ratio of the negative 

 induction change when field is withdrawn, with and without 

 vibrations (B v — R v /B — R), distinguishes the qu< nched from 

 the annealed condition. In the quenched metals this ratio 

 does not ditf'er greatly from 1*3 for all values of field other 

 than the lowest. In the annealed metals, on the other hand, 

 it varies largely with field, reaching a maximum value in 

 annealed nickel (5*8) and minimum values (1*6) in annealed 

 iron and steel, when H is approximately equal to 2. (In 

 quenched iron a corresponding minimum is merely indi- 

 cated.) In annealed nickel B v — R v /B — R is much greater 

 in low than in high fields. In annealed iron and steel this 

 difference is less marked. 



Coercive Force, Ret( utility, and Hysteresis in Relation to 

 Field. — These are increased or decreased as the field is low 

 or high, but in quenched nickel the decrease of residual 

 magnetization, if it exists at all, is very small. 



The relative increase of coercive force is greater in an- 

 nealed and quenched niekel than in iron and steel. Increase 

 passes into decrease earlier in the case of coercive force than 

 of residual magnetization. The increase of hysteresis loss 

 in low fields is relatively greater than its decrease in high 

 fields, and increases with the increase of vibrational intensity. 

 In annealed and quenched nickel its relative increase is enor- 

 mously great in the lowest fields used. There is nothing corre- 

 sponding to thiswlien h'eld is unduly decreased in iron and steel. 



Coercive Force and Hysteresis Loss in Relation to Induction. 

 — In all cases for the same value of induction at cyclic ex- 

 tremes, coercive force and hysteresis loss are decreased. 

 At high inductions the decrease of energy loss is relatively 

 smaller than at lower inductions. At very low inductions 

 the decrease of loss produced by vibrations is a decided 

 maximum in annealed nickel. 



Reteniivity in Relation to Induction. — Vibrations do not 

 in all cases decrease residual magnetization. In quenched 

 nickel, when the field producing the same induction of the 

 order of hundreds in both cases is withdrawn, the residual 

 magnetization is greater with than without permanently acting 

 vibrations. At low inductions in quenched iron R v may 

 equal R ; in all other cases R v is less than R. 



