24 ART. 6.— S. KUSAKABE : 



which is the expression for the residual surviving the couple, 

 since in this case n being equal to p the specimen is free from any 

 external couple. 



Taking the difference of a for two consecutive values of *, we 

 have 



At 



* fo ,&^-^+j)ML <0 (14). 



J {p + r+t+l}[p + t+l\ 



which is evidently negative, because any rectangle is smaller than a 

 square when their periphery is given. Also, the limiting value of a 



as well as of , is zero for t=cc . Thus we have. 



A£ 



Proposition II. The residual diminishes with the lapse of time and 

 'ultimately disappears wholly after an infinite time. Consequently, the 

 yielding is elastic, and recovers wholly if the couple is removed for an 

 infinite duration. 



The differential for the unit increase of r is 



Ar J [p + r + t+l] 



which is positive since the fraction is greater than unity ; but the 

 second differential being 1 negative. We have. 



Proposition III. The residual — so-called set — increases with the 

 increase of the time during which the couple acted on the specimen. 



Here it must be remarked that the expression for the recovery 

 may be deduced from that for the residual. It is given by 



ß - hloa n2p+r+l }I\p +r+t+l}rip + t +\} m 



( - h l °v r{p+r+i}r{ P +A}r{ip+r+t+i}rit+\} K ;> 



where r expresses the time-element during' which the specimen 

 remained acted by a constant couple p. Thus it is evident that the 

 curve of recovery is a little different from that of yielding whose 



