Brown — Mechanical Stress and Magnetisation of Nickel. 39 



No. 16 wire was placed vertically inside the long solenoid with a 

 longitudinal load on its lower end equivalent to 10* grammes per 

 square centimetre ; and it was made to oscillate round its own axis, 

 the amplitude of the oscillation being read off at every fifth or 

 tenth vibration until 70 complete vibrations had been accomplished. This 

 was done first wlien there were no magnetic fields round the wire, and then 

 when there were magnetic fields round it of different strengths up to a 

 maximum of 20 c.g.s. units. The load on the wire was then changed to 

 2 X 10* grammes per square centimetre, and another similar series of 

 observations taken ; the No. 14 wire was then put in place of the No. 16, and 

 another set of observations taken when the load on it was at the rate of 

 2 X 10* grammes per sq. cm. 



The results obtained in the three cases were then plotted in curves, to the 

 same scale as those given in fig. 2, with the numbers of vibrations as abscissae 

 and as ordinates the corresponding values of the amplitudes of the oscil- 

 lations ; the curves so obtained were flatter than those got with the nickel wire, 

 the rates of damping of the oscillations were less rapid, and the range more 

 limited than in the ease of nickel. 



The following Table gives the values of the amplitudes of oscil- 

 lation with nickel and iron wires, when tested under the same conditions of 

 magnetic field ; botli wires were of No. 16 gauge; the load on tlie nickel 



Tabivr IV. 



