128 



Scientific Proceedings, Royal Dublin Society. 



obtain the same current strength from different alternators, and it was found 

 that the current most suitable was that which gave a transverse field of 

 250 units. Observations were made of the torsional subsidence of the wire 

 when it was subjected to the influence of transverse magnetic fields of 

 strength 250 units, and of frequencies 25, 50, 100, and 200 per second 

 respectively. A few of the results are given in Table II, where for com- 

 parison there are also given in column 2 the values obtained when there was 

 no transverse field on the wire. The length of the wire was 75 cms., and the 

 oscillating load 2 x 10 5 grammes per sq. cm. with 2670 grammes on the scale- 

 pan end of the torsionless floss-silk string. 



Table II. 



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

 H = 250 units. 



From the values in Table II it will be seen — when transverse magnetic 

 fields of 250 units at different frequencies are applied — that as the frequency 

 is increased, the damping of the torsional oscillations is decreased. For a 

 frequency of 200 per second the amplitude of the 70th oscillation is increased 

 by about 4 per cent, as compared, with the amplitude when there was no 

 field round the wire ; also, when the frequency is increased eight times, the 

 amplitude of the 70th oscillation is increased about 23 per cent. 



The soft nickel wire was replaced in the apparatus by a hard nickel wire 

 of rigidity about 810 x 10 G grammes per sq. cm. This wire was of the same 

 length, had on it the same load, and was put through exactly the same series 

 of tests as was the soft wire. The more important of the results obtained 

 are given in Table III, the observed values of the torsional subsidence were 



