UPON MAGNETISATION, AND CONVERSELY, IN IRON, STEEL, AND NICKEL. 507 



vibrations are superposed (A conditions) at all stages of the smaller of the normal 

 loops (lower field). The dotted loops, on the other hand, measure the hysteresis 

 loss for permanently acting vibrations (B conditions) for the same maximum 

 value of field (compare with the smaller normal loops in each figure), and also 

 for the same maximum value of induction (compare with the larger normal loops in 

 each figure). 



Fig. XV. shows the effect of permanently acting vibrations only for quenched iron 

 upon hysteresis loss (and residual magnetisation for the same maximum value of in- 

 duction (B = 85) already referred to). The dotted and full-line curves have the same 

 signification as before. 



Attention may here be called to the shape of the loops in the case of quenched 

 nickel. The areas are bounded practically by six straight lines, rather more marked 



QUENCHED 

 FIG.XV iron 



A. and B. CONDITIONS. 

 100 — 



B 



B v A CONDITIONS B N 



B CONDITION! S 



when the induction is of the order of thousands (fig. XVII.) than hundreds (fig. XVI.). 

 The abrupt changes which occur during the cyclic process may be compared with those 

 first observed by Nagaoka # when nickel wire is subjected to torsion combined with 

 longitudinal pull. The same abrupt changes were obtained without load. 



Note that vibrations have little or no effect in lessening the rectilinear character 

 of the normal loops. Indeed, for low values of field, vibrations rather increase this 

 characteristic than otherwise. 



Coercive Force. — The general effect of permanently acting vibrations is the same 

 in the quenched as in the annealed condition, and the same differences also exist when 

 quenched nickel is compared either with quenched iron or steel. These latter metals 

 call for no further remark. Their behaviour is normal. But the decrease of coercive 

 force for the same value of low induction is less in quenched than in the annealed 



* Magnetic Induction in Iron, Ewing, 3rd ed., p. 248 ; Jour. Coll. Science Imp. Univ. Japan, vol. ii. p. 304. 

 TRANS. ROY. SOC. EDIN., VOL. XLV. PART II. (NO. 17). 71 



