ON THE MODULUS OF TORSION AL RIGIDITY OF METAL WIRES. 



33 



lif.-itings, and the j>eriod became finally nearly constant. The calculation of the 

 rigidities was complicated by the fact that the wire gradually drew out under the 



3-310 



oo.i 



3 

 * 



8 



5 



"63-306 



S 



3304 



MM 



00 



I 



/ 



y 



too' 





O. 



tl 



7^ 



200' 300' 



Amplitude Of Vibration. 



yoct 



s-J"3. 

 I 



n 



*m 



Soi'^ 



Diagram VI. Platinum wire. Dotted lines show the alteration of the logarithmic decrement of the 

 torsional oscillations with the amplitude of vibrations. Continuous lines show the effect of the 

 amplitude on the period of torsional vibration. 



slight tension to which it was subjected. The increase of length amounted to 

 1205 centim. at the end of the experiment. 



The manner in which the rigidity modulus altered with the temperature can be 

 seen from Diagram VII. The curve obtained is similar to that given by soft iron, 

 but it is more nearly a straight line. 



In order that the rate of increase of rigidity with time might be more easily seen, 

 the rigidities at various temperatures were plotted against the lengtlis of time for 

 which the wire had been kept at those temperatures. The resulting curves (which 

 are not given) were similar to those obtained for iron and platinum. 



VOL. cciv. A. F 



