138 H. Nagaoka on Hysteresis attending Change of 



maxima would probably have been produced at or near 

 these places. (For measurements see Table IV.) 



Fig. 4 (PI. II.) represents double magnetic cycles made 

 on a wire 14*2 centim. long and 2*83 millim. thick. When 

 the maximum elongation was reached in field 75 (which is 

 slightly greater than in fig. 2, because the wire is shorter), 

 the magnetizing force was decreased and a cycle performed. 

 The cyclic curve is b c d e f g h. The curve evidently shows 

 hysteresis, and is symmetrical with respect to the vertical axis. 

 When this cycle was completed, the field was further in- 

 creased till a sufficient decrease of elongation set in, and a 

 second cycle with greater range was gone through. The 

 curve (shown in dots) is d! e'f'g' It h' m rip' q' r' s' t' v! , and is 

 in every respect similar to that given in fig. 2 



The experiments above described prove that elongation 

 in iron and contraction in nickel by magnetization both show 

 decided hysteresis. The curve of hysteresis is symmetrical 

 with respect to the line of zero magnetizing force, so that the 

 elongation or contraction during cyclic changes is an even 

 function of the magnetizing force. When the wire is mag- 

 netized, it cannot be brought to its original length by simple 

 reversal of field. While this paper was passing through the 

 press, Mr. Lochner published the results of his investigation 

 on the change of length in soft iron by magnetism, in the 

 December number of this Magazine. The curve given in 

 fig. 3 of his paper distinctly shows hysteresis. 



Some of the elongations measured in nickel and iron wires 

 are given in the following Tables. 



Table I. — Nickel wire : Z=19*4 centim., d=2'04 millim. 



H. 



1 

 -^Xl0*. 



H. 



36 



-fxios. 



H. 



'I Xl08 - 











43-6 



- 3-8 



44-3 



20 



1-2 



2-2 



41-5 



- 24 



420 



2-8 



1-7 







38-2 







36-8 



3-6 



25 



- 1-8 



34-1 



1-6 



32-7 



4-7 



33 



- 2-6 



30-3 



33 



29-9 



66 



4-2 



- 4-5 



27-8 



4-1 



27 4 



8-5 



14-8 



- 6-7 



28-7 



46 



27-8 



92 



25-4 



- 7-8 



32-4 



5-4 



286 



102* 



53-0 



- 8-9 



39-0 



63 



29-6 



73 



49-8 



-10-1* 



519 



7-9 



341 



5-8 



48-7 



- 79 



502 



100 



503 



47 



464 



- 57 



48-2 



102 



53-7 



* Give maximum magnetizing field. 



