ON THE MODULUS OF TORSIOXAL RIGIDITY OF NfETAL WIRES. 



39 



the harder metals ; for the oscillations damped down so quickly that only a 

 comparatively small number took place. The difficulties of observation were also 

 increased by the fact that, although a light aluminium vibrator was used with the 

 wire, it underwent a considerable elongation, especially at the higher temperatures. 

 At the second heating to 100 C. this elongation was so great that the vibrator 

 moved about in jerks as the wire guve way, and rendered timing impossible. 



It was found that the rigidity of the wire at the ordinary lalx>ratory temperature 

 was diminished by repeated heatings, and that when the wire was allowed to rest at 

 one temperature its rigidity increased as time went on. The curve in Diagram VIII. 

 is drawn through the mean of the observations at the different temperatures. 



1 



Temperature Centigrade. 

 Diagram VIII. Showing the effect of temperature 011 the modulus of rigidity of tin and of lead wire- 



