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XIII. 



THE SUBSIDENCE OF TORSIONAL OSCILLATIONS OF NICKEL 

 AND IRON WIRES WHEN SUBJECTED TO THE INFLUENCE 

 OF TRANSVERSE MAGNETIC FIELDS UP TO 800 C.G.S. UNITS. 



By WILLIAM BROWN, B.Sc, 

 Professor of Applied Physics, Royal College of Science for Ireland, Dublin. 



Read March 28. Published May 29, 1916. 



In a recent communication 1 there was brought before the Royal Dublin 

 Society the results of some experiments on the behaviour of nickel wires 

 when they were made to oscillate in transverse magnetic fields, both direct 

 and alternating, the maximum value of the field used being 200 c.g.s. 

 units. The present communication is in continuation of the above-mentioned 

 work, and gives results obtained with nickel and iron wires when magnetic 

 fields up to maximum value of 800 c.g.s. units were employed. In this 

 case the transverse magnetic fields used in the experiments were produced in 

 a soft iron tube by means of five insulated copper wires arranged in series 

 inside the tube, the return wires of the circuit being two metres away from 

 the iron tube. 



For these experiments a new iron tube with a slot down its whole length 

 was obtained, the tube being 215 cms. long, 2-54 cms. external diameter, 

 1*6 cms. internal diameter ; breadth of face of slot, 0"47 cms. ; and width of 

 slot, 0.8 cm. — that is, 3 mm. wider than the slot in the tube previously 

 used. The copper wires in the tube were each - 4 cm. diameter, and were 

 each insulated by being painted with two coatings of anti-sulphuric enamel, 

 then one layer of thin silk ribbon, and when they were finally assembled — 

 that is, grouped four wires round one in the centre of the tube — they were 

 bound firhrly together, and given a coating of shellac varnish. The wires 

 were then firmly fixed in the tube, and the circuit arranged so that the current 

 went through the five wires in the same direction, and produced a transverse 

 magnetic field in the gap of the iron tube. The relation between the current 

 in the copper wires and the magnetic field in the gap was found as before 



1 Scient. Proc. Royal Dublin Soc, 1916, vol. xv, No. 9, p. 99. 



SCLENT. PROC. K.D.S., VOL. XV., NO. XIII. 



