160 



Mr. C. Barus on the Viscous Efect of 



effect, §§ 4, 5. This is attempted in Table III., in which tor- 

 sional stress is applied cyclically. The viscous behaviour is 

 studied at each of these successive stages of increase or 

 decrease, as shown in the first column, t, of the table. As 

 before, the length of the system of two wires, L = ^ + ?' = 30 

 centim.H-30 centim. : diameter, 2/9 = '081 centim. The final 

 column A(<^ — ^'), being the detorsio" from the beginning 

 to the end of the first minute after twisting, may be taken 

 as an index of the rate of deformation. In the first and 

 second cycles twist is imparted positively ; in the third cycle 

 negatively. To follow the sequence of observations it is 

 safliicient to consult the time-column. 



Table III. — Viscous Deformation in case of Cyclic Twisting. 



First Cycle. 



Twist Increasing. 



Twist Decreasing. 1 



Rate of 

 Twist, T. 



Time. 



(0-0') X 10°. 



^-/s.103 



xio«. 



Eate of 

 Twist, T. 



Time. 



(0-*')xlO«. 



A(0-0') 

 XlO«. 



T 















h m 







•000 











•000 



12 31 

 32 

 33 

 34 

 35 

 1 18 

 30 







- 10 



- 20 



- 27 

 -107 

 -120 



-10 





h lu 

















•009 



10 36 







3 



•009 



12 26 





- 8 





37 







•0 







27 











38 



3 



11 







28 



- 8 







39 



5 



\-b 







29 



-15 







40 



6 



1-9 







30 



-21 





•017 



10 41 







9 



•017 



12 21 





- 5 





42 







•0 







22 











43 



9 



1^4 







23 



- 5 







44 



15 



2-8 







24 



-12 







45 



20 



3-2 







25 



-17 





•026 



10 46 







14 



•026 



12 16 





- 7 





47 



b 



•6 







17 



- 6 







48 



14 



1^5 







18 



- 7 







49 



23 



2-5 







19 



-12 







50 



27 



2^8 







20 



-15 





