102 



Scientific Proceedings, Royal Dublin Society. 



200 units in each case. The column marked (A.C.) gives the values when a 

 transverse alternating magnetic field of 200 units, and frequency 50 per 

 cent, per second, was on the wire ; and with the full longitudinal load on, 

 that is, the same load as was on when the values in column marked (D.C.) 

 were observed. 



Table I. 

 Bigidity = 708 x 10 6 grammes per sq. cm. 



From the values in the third and fourth columns in Table I, we find that 

 the alternating field decreases the amplitude of the 70th vibration by 10£ per 

 cent. ; and from those in the second and third columns we see that the extra 

 longitudinal pull on the wire, due to 1670 grammes, raises the damping curve, 

 the amplitude of the 70th vibration being increased about 7 per cent. This extra 

 weight being always on in the further experiments, comparison can be made 

 on the effects of direct and alternating magnetic fields, and also when 

 alternating fields of different frequencies are employed. 



In order to find the effect of transverse magnetic fields of different 

 frequencies on soft nickel wire, arrangements were made to obtain the same 

 value of current from three different alternators, and it was found that the 

 current most suitable was that which gave a transverse magnetic field 

 of 65 units. Observations were made of the torsional subsidence 

 when the wire was subjected to magnetic fields of frequencies 25, 50, 100, 

 and 200 per second; and the results are given in Table II, where, for 



