404 Scientific Proceedings, Royal Dublin Society. 



two apparently different physical states, namely — (1) in the condition in which 

 it came from the manufaoturer; (2) in its condition after being heated /o»r 

 times to a bright-red heat ; tlie rigidity was found to be the same in the two 

 conditions, that is about 685 x 10" grammes per square centimetre. 



The wire was tested for subsidence of torsional oscillations when in the 

 three conditions : (1) as from the manufacturer, (2) after being heated once. 

 (3) after being heated three times more. Tests were made in both direct and 

 alternating magnetic iields of values 3, 6, and 32 c.g.s. units, and the rate 

 of subsidence of the torsional oscillations was identical in every case ; the 

 amplitude of oscillation fell from 300 to 290 after 70 complete vibrations 

 had taken place. This small decrease of 10 divisions only in the amplitude 

 of oscillation after 70 vibrations shows that tl>e wire is remarkably ductile ; 

 in fact, it behaves in this matter of damping of torsional oscillations very 

 mucli like a soft nickel wire when oscillating in a direct longitudinal 

 magnetic field of 200 c.g.s. units.^ The longitudinal load on the wire during 

 these tests was 1 x 10' grams per sq. cm., and when tested for fatigue in a 

 magnetic field of 6 c.g.s. units — the field in which the peak of the Wiedemann 

 curve occurred — the maximum fatigue was only 0"11 after the application of 

 the alternating magnetic field for one hour. 



Section III. 

 Other Alloys. 



It may be as well to record here the negative results obtained with two 

 wires that are much used in commercial work for resistances, and are known 

 by the trade names Nickeliu and Concordin. Niekelin would, at first sight, 

 suggest a material which contained a large proportion of nickel, and this 

 wire was put through the tests for damping of torsional oscillations before 

 being analyzed chemically. It is a copper-nickel alloy, having Cu = 60 per 

 cent., Ni = 40 per cent. This material is perfectly non-magnetic ; for, when 

 tested as above for damping of oscillations in various direct and alternating 

 magnetic fields, it gave exactly the same damping curves in every ease, 

 that is, the amplitude of oscillation fell from 300 to 271 after 70 complete 

 vibrations had taken place. 



Concordin, an iron-nickel-chromium alloy, also non-magnetic, was tested in 

 the same manner as niekelin, and gave exactly the same damping curves in all 

 the magnetic fields, whether D.C. or A.O., the amplitude of oscillation falling 

 from 300 to 279 for 70 complete vibrations. 



For assistance in making some of the observations I am indebted to the 

 Eev. Br. M. C. Wall, a fourth-year Teacher in Training in this College. 



1 Scient. Pioc. Koy. Dub. Soc, vol. xiii, 1911, No. 3, p. 3.5. 



