r 28 ] 



III. 



MECHANICAL STRESS AND MAGNETISATION OF NICKEL 

 (PAET II.), AND THE SUBSIDENCE OF TORSIONAL 

 OSCILLATIONS IN NICKEL AND IRON WIRES WHEN 

 SUBJECTED TO THE INFLUENCE OF LONGITUDINAL 

 MAGNETIC FIELDS. 



Bt WILLIAM BROWN, B.Sc, 

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



[Read Jancaey 24. Ordered for Publication Febihtaiiy 14. Published April 1.5, 1911.] 



It was shown in Part I. of tliis paper' that when a nickel wire was 

 subjected to simultaneous longitudinal and circular magnetism, the maximum 

 twist of the free end of the wire was greater the greater the longitudinal 

 load ; this result was obtained by observing the effects of three different 

 longitudinal loads on the end of the wire under test, the largest load being 

 at the rate of 3 x 10' grammes per square centimetre. 



The first division of the present communication gives results obtained 

 when the same and higher loads were employed, as well as higher longitudinal 

 magnetic fields ; and for this work a new batch of pure nickel wires was got 

 from the manufacturer. One of these wires was prepared in the manner 

 explained in Part I. of this'paper,' the degree of magnetic softness obtained 

 being between Hj and Hj of the arbitrary scale there used, that is, the wire 

 had a simple rigidity of about 720 x 10^ grammes per square centimetre, 

 and was a full size No. 16, of diameter 0'168 cm. and of cross-sectional 

 area 22"17 x 10"' square centimetres. 



This wire, with a given longitudinal load on its lower end was suspended 

 vertically in the middle of a long solenoid, by means of which longitudinal 

 magnetic fields of definite values could be applied to it. The apparatus 

 being arranged as already indicated,^ an electric current was sent through 



1 Scient. Proc. Roy. Dub. Soc, vol. xii., No. 37, pp. 500-518. 

 ' Loo. cit. 



