ON THE MODULUS OF TORSIONAL RKJIDITY OF METAL WIRES. 



dynes per sq. centim., and the "temperature coefficient" ft = "0001018. 

 alteration of rigidity with time can be easily seen from Diagram V. 



31 

 The 



638 



r- 



Ed'. 



3 u> 5 



Time In hours. 



Diagram V. Showing the alteration of the modulus of rigidity of platinum wire with time. 



It is curious that on December 13, the rigidity at 98 '63 decreased as time went 

 on. On the following day it was practically constant. 



Table VI. contains the values of the logarithmic decrements obtained at the 

 various temperatures. Each is the mean of two or three observations. 



