UPON MAGNETISATION, AND CONVERSELY, IN IRON, STEEL, AND NICKEL. 501 



in the manner described on p. 496. The dotted and continuous lines represent the 

 cycles with and without vibrations. Figs. VI. and VII. show, for annealed steel, loops with 

 and without vibrations, corresponding to the following four maximum values of field, 

 viz. H = , 16, T46, 2*6, and ll'O. The induction at cyclic extremes covers the wide 

 range between B = 56 and B= 15,750 without vibrations. These loops are typical of 

 others taken at intermediate values of field. The cyclic curves for annealed iron are 

 essentially similar to those for annealed steel (see fig. II., curve 3). 



In figs. VII. and VIII. the smaller and larger of the two continuous-line loops (without 

 vibrations) enable comparison to be made with the dotted-line loops (with vibrations) 



ANNEALED 



B. CONDITIONS 



15000 



•6 -8 



FIG VIII NICKEL 



B v 



for the same value at cyclic extremes of field and induction respectively, 

 is for annealed steel, fig. VIII. for annealed nickel.* 



Fig. VII. 



EXPERIMENTAL RESULTS. 



Coercive Force. — Permanently acting vibrations increase coercive force when the 

 values of field are low. This effect soon disappears as the fields are taken higher, and 

 thereafter vibrations decrease coercive force. For the same value of induction, 

 coercive force is always decreased. 



* Fig. VIII. is one of the earlier experiments, and a thread was not introduced between the lever and the nickel 

 wire under test. These observations have been repeated with this alteration, and the larger loop ought to be more 

 sheared over than shown in this figure. The coercive force remains the same, the residual magnetisation is reduced 

 to within 15 C.G.S. units of the dotted loop, and the value of H is increased to l - 25. These corrections give the 

 values of R and B at the cyclic extreme the same as in fig. V. for the same value of field. The increase of per- 

 meability and residual magnetisation is due to a minute torsional stress imparted to the nickel wire when no thread is 

 introduced. The two smaller loops with and without vibrations remain exactly as shown, as also fig. XI., p. 503. The 

 experimental results, therefore, relative to coercive force and hysteresis loss, remain as stated in the following section. 



