Brown — The Subsidence of Torsional Oscillations. 



131 



Table IV. 

 Rigidity =? 810 x 10 6 grammes per sq. cm. 

 H = 250 units. 



From Table IV, by comparing columns 2 and 3, it will be seen that when 

 an alternating transverse magnetic field of 250 units and frequency 25 per 

 second is applied to the hard nickel wire, the damping of the torsional oscilla- 

 tions is increased, that is, the amplitude of the 70th oscillation is decreased by 

 nearly 9 per cent, as compared with nearly 16 per cent, when the wire was 

 soft (Table II) ; also, from columns 3 and 6, when the frequency of the field 

 is increased eight times, the damping of the oscillations is decreased about 6 per 

 cent, as compared with 23 per cent, when the wire was soft (Table II). 



Section II. 



Iron Wires. 



A No. 16 iron wire of rigidity 780 x 10° grammes per sq cm. was put into 

 the apparatus in place of the hard nickel wire, and it was put through the same 

 series of tests as were the nickel wires, that is, for the whole length of the wire, 

 225 cms., the tests were made in magnetic fields up to a maximum value of 

 200 c. g. s. units, and for the length of 75 cms. in magnetic fields of maximum 

 value 800 units. For the wire 225 cms. long the load used was the same as 

 that employed for the nickel wire of the same length, namely, an oscillating 

 load on the end of the wire equivalent to 2 x 10 3 grammes per sq. cm. and a 

 weight of 1670 grammes on the scale-pan end of the torsionless silk string. 1 

 For the wire 75 cms. long the oscillating load was the same, but the weight 



1 Loc. tit. 



