IQ ART. 6.— S. KUSAKABE : 



Fio-s. 19-22, PL XL, which shows steady increase of the twist even 

 after the lapse of many thousands of minutes. 



Recovery from the Yielding : — To examine whether the 

 yielding above investigated is elastic or permanent, a specimen was 

 subjected under a constant couple during one hundred and sixty- 

 seven hours, and then it was suddenly released from the couple. 

 The amount of residual was observed from instant to instant with 

 the corresponding time-record. The result is shown in Figs. 23 and 

 24 in PL VIII. This curve of recovery resembles, as a whole, that 

 of yielding. 



Again, to investigate the influence of the recovery on the cycles, 

 a specimen, which had been subjected under a constant couple during 

 three hundred and six and a half hours, was twisted to and fro 

 cyclically. Gradual recovery, as is shown in Fig. 25, PL XII., may 

 be traced along the whole cycle. Comparing this with that drawn 

 in PL VI., both of which were treated in one and the same manner 

 as regards the cyclic process, the effect of the recovery will be more 

 clearly understood. Fig. 26 in PL XIIL, shows the result of the 

 next experiment conducted on the same specimen in a similar manner. 

 Here, the form of curve, as a whole, has a centre of symmetry coincid- 

 ing with that of the cyclic process. No possible explanation for this 

 non-coincidence of the last two curves can be found but that, in the 

 first case, in which the specimen had been kept under the couple 

 during very long time, the total yielding having been very great, the 

 specimen had a greater tendency than in the other case to recover 

 from the yielding when the couple was withdrawn. 



THE HYSTERESIS FUNCTION. 



From what has been explained in the foregoing pages, we see 



