VIBRATION OF FERROMAGNETIC WIRES. 9 



frequency and the second in a lower one, the difference amounting 

 in each case to about 20. The tirst maximum is also of a frequency 

 higher by at least 2.5 times than that calculated on the conside- 

 ration that tlie phenomenon is due simply to the elastic vibration 

 of the wire. 



Instead of attaching a weight to the free end of the wire, the 

 same end was stretched by means of a spiral spring fixed to the 

 stand. Varying the frequency of the intermittent or alternate 

 current, the maxima and minima of the amplitude of vibration were 

 also observed, as shown in Fiü". o. In this case, the first maximum 

 occurred at a frequency of about 75 per second for iron as well as for 

 nickel, and the second at a frequency higher than IGO per second for 

 these two metals. These positions of maxima and minima were almost 

 independent of the tension arid of the length of the spring. 



à 



so 



Iron wire. 



100 



ISO 



Fi 



■7^ 



a 



xio 



60 



Nickel wire. 



■11 



Whether these complicated phenomena nre capable of being 

 explained simply by the elastic vibration and the magnetic change 

 of length without taking account of the time-lag, or whether they 

 prove the existence of this effect, requires further experimental 

 and theoretical considerations. 



