36 



Scientific Proceedings, Royal Dublin Society. 



initial amplitude of 300 divisions on the scale, or from an angular twist on 

 the lower end of the wire of 7-|°. 



These results are also shown as curves in fig. 3, in wliioh the abscissse are 

 the values of the lougitudinal magnetic field that was round the wire when 

 being tested, and the ordiuates the corresponding values of the amplitudes 

 after 70 vibrations had been accomplished. 



Table III. 



The numbers at the right-hand end of each curve give the longitudinal 

 loads iu grammes per square centimetre that were on the wire when it was 

 being tested. The curves show that the greatest damping of the torsional 

 oscillations takes j^lace iu each case when tlie wire is surrounded by a 

 longitudinal magnetic field of the same value as was round tlie wire when 

 the maximum twist for the given load was obtained, as is exhibited in fig. 1 — 

 that is, tlie crests of the curves in fig. 1 take place in tlie same longitudinal 

 magnetic fields as the hollows of the curves in fig. 3, or the magnetic field in 

 which the maximum effect takes place is larger the larger the lougitudinal 

 load on the wire. 



Q-ray and Wood' have also shown that tlie effect of increasing the weight 

 of the vibrator on the end of the wire is to give a greater maximum effect and 



' Loc. cit. 



