44 



Scientific Proceedings, Royal Dublin Society. 



for this frequency of an applied A.C. field it was found that the wire with 

 this load on was thrown into such a state of vibration that it was impossible 

 to take readings. The natural vibration frequency of the wire in this case 

 was probably some harmonic of that of the applied field. 



Taking the values of the contraction in Tables I, II, and III for the 

 magnetic fields of 200 units, we find generally that, as the load on the wire is 

 increased the contraction is decreased. When the load is increased 16 times 

 the contraction is decreased about 10 per cent, for the longitudinal magnetic 

 field, and about 30 per cent, for an alternating magnetic field of frequency 

 150 per second. For the same magnetic field of 200 units, when the 

 frequency of the applied alternating magnetic field is increased 6 times the 

 contraction of the wire is increased by about 24 per cent, for the light load, 

 13 per cent, for the middle load, and 9 per cent, for the highest load used. 



In Tables IV and V are given the results obtained with a wire having a 

 rigidity of about 708 x 10 G grammes per sq. cm. "When the alternating 

 magnetic fields were applied to the wire when it had the light load on, the 

 vibrations were such that the readings on the microscope could not be taken. 

 The values of the contraction obtained with this load, (0"125 x 10 5 ) grammes 

 per sq. cm. in the direct longitudinal magnetic field, are given in Table IV 

 in the column marked d.c. 



Table IV. 

 Rigidity = 708 x 10 s grammes per sq. cm. 

 Load = - 5 x 10 5 grammes per sq. cm. 



