556 



Seientific Proceedings, Ror/al Dublin Society. 



Table III. 

 Rigidity = 790 x 10* grammes per sq. cm. 



These figures iu Table III, as well as those in Table I, sliow that for the 

 wire in these comparatively hard states, the application of alternating 

 magnetic fields of frequencies higher than 150 per second have very little 

 effect in increasing tlie subsidence or damping of the oscillations ; for softer 

 wires, as shown below, the damping decreases as the frequency of the magnetic 

 field is increased, tliough at a slow rate. 



The wire was again removed, and heated three times to a chenuj red heat iu 

 the same manner as before, and when cold its rigidity was measured and 

 found to be about 730 x 10* grammes per sq. cm. It was again put into the 

 solenoid and tested under exactly the same conditions as formerly for both 

 fatigue and the subsidence of torsional oscillations. The wire being now 

 much softer, the fatigue was less than when in the hard state ; the maximum 

 was found to be 0' 147 for the alternating magnetic fields at the two frequencies 

 tried, and took place in six minutes when the frequency was .50, and in four 

 minutes when the frequency was 100, per second. 



The observations for the subsidence of torsional oscillations were taken as 

 before for both D. C. and A. C. magnetic fields at five different frequencies, and 

 some of them are given in Table IV. 



Table IV. 

 Higidity == 730 x 10* grammes jier sq. cm. 



