136 Scientific Proceedings, Royal Dublin Society. 



oscillations is increased. By comparing columns 3 and 6 it will be seen that 

 when the frequency of the field is increased eight times, the amplitude of the 

 70th oscillation is decreased by nearly 13 per cent., and by comparing 

 columns 2 and 6 the amplitude is decreased nearly 30 per cent, in a field of 

 strength 250 units and of frequency 200 per second. 



As a test for the presence of eddy currents in a wire due to high trans- 

 verse magnetic fields, and their action on the damping of the torsional oscilla- 

 tions, a soft No. 16 copper wire, 75 cms. long, and loaded the same as were the 

 nickel and iron wires, was put into the apparatus, and a series of tests made. 

 Observations of torsional subsidence were made with magnetic fields of H = 0, 

 H = 800 D.c, and H = 800 a.c. of frequency 50 per second, and the values 

 obtained in the three cases were identical. 



For assistance in preparing the apparatus and in making some of the 

 observations I am indebted to Mr. E. Macaulay, the Electrician at the 

 Eoyal College of Science. 



