Brown — The Subsidence of Torsional Oscillations. 9 



From the values in Table VIII it will be seen that the damping of the 

 torsional oscillations is increased slightly by an increase in the load : by 

 comparing the amplitudes of the 70th oscillation in each case. When the 

 longitudinal load is increased four times, there is a decrease of about 5§ per 

 cent, when a D. C. magnetic field is round the wire, and about 6-J- per cent, for 

 an A. C. magnetic field of frequency 250 per second. In Table IX, which 

 gives the values for the wire in the softer state, there is a curious result 

 when the light load is used, that is, there is less damping of the torsional 

 oscillations with an A. C. magnetic field of frequency 250 than with an 

 A. C. field of frequency 50 per second, which is the reverse of what occurs 

 with the higher loads. In fact, a soft wire with a small load seems to behave 

 in the same way as a hard wire under all loads. The damping of the torsional 

 oscillations is much more pronounced when the wire is soft than when it is 

 hard ; and by taking the same range of loads as was taken above for the hard 

 wire, that is, from 1 x 10 5 to 4 x 10 5 grammes per sq. cm., the amplitude of 

 the 70th oscillation is decreased about 40 per cent, for a D. C. magnetic field 

 and about 30 per cent, for an A. C. magnetic field of frequency 250 per 

 second. 



The effect of an increased longitudinal load in changing the subsidence of 

 torsional oscillations is better seen from Table X, which gives in each case, 

 for six different values of the load, the difference in the amplitude after 70 

 complete vibrations when a D. C. magnetic field was round the wire, and 

 when A. C. magnetic fields of frequencies 50 and 250 per second respectively 

 were applied. 



Table X. 

 Rigidity = 770 x 10 6 grammes per sq. cm. 



These values are shown as curves in fig. 2 (p. 10), which shows that the 

 D. C. and A. C. damping curves would be identical with a load of about 



SCIENT. PROC. R.D.S., VOL. XV., NO. I. B 



