Brown and Smith — Subsidence of Torsional Oscillations. 221 



The results in Table III are shown as curves in the figure (except those 

 values in column four, which are left out so as not to crowd the figure) where 

 the values in column one are taken as abscissae, and the corresponding 

 values in the otlier column as ordinates. 



■2 300 



200 



100 



•^ 



20 30 40 50 



Number of Vibrations 



70 



The curve marked D. C. is that obtained when a direct longitudinal 

 magnetic field is round the wire ; and the four top curves are those obtained 

 when equivalent alternating magnetic fields of frequencies 20, 40, 50, and 

 100 per second are round the wire ; whilst the dotted curve marked E is tlie 

 one obtained when tlie Eartli's vertical force, 0'45 c.g.s. unit, is on the wire, 

 this latter being put in for comparison. 



The effect of an alternating magnetic field in decreasing the damping of 

 torsional oscillations in a soft nickel wire is very strikingly sliown by these 

 curves. The damping curve for a frequency of 100 per second, and an 

 alternating magnetic field of 17 c.g.s. units, with a load of 10' grammes per 

 sq. cm, on the wire, is almost identical with a damping curve obtained 



