[ 500 i 



XXXVII. 



MECHANICAL STRESS AND MAGNETISATION OF NICKEL, 



Tart I. 



By WILLIAM BEOWN, B.Su., 

 Professor oE Applied Physios, Royal College of Science for Ireland. 



[Ordered for PulJication Octo]i];u 21. ruljlished Dicemder 6, 191(1.] 



In 1883 it was observed bj' Knott' that the torsion produced on a nickel wire 

 under the combined influence of longitudinal and circular magnetism was in 

 a reverse direction to that produced ou an iron wire ; and a summary of tlie 

 subsequent work done in this part of the subject up to 1900 is given in 

 Nagaoka's report on Magnetostriction for tlie International Congress on 

 Phj'sics.^ As far as tlie present writer knows, no further work — bearing 

 mainly ou the twist of nickel wires when magnetised longitudinally and 

 circularly — has been done except that of Shimizu and Tanakadate,' wlio 

 found that the Wiedemann effect in nickel practically vanishes at the critical 

 temperature of tlie metal. 



The present paper gives the results of some experiments on tlie 

 magnetisation and torsion of nickel wire, the apparatus and experimental 

 arrangements being the same as were employed bj' the author in the work 

 ou mechanical stress and magnetisation of iron.^ In this case, also, five 

 different degrees of hardness were adopted, which were obtained by heating 

 the wires to a cherry-red heat (in a darkened room) by means of a broad 

 Bunsen burner when they were hung vertically and subjected to different 

 longitudinal loads. In the experiments for testing the effect of temper on the 

 torsion and magnetism, No. 16 size wires of pure nickeP were employed, 

 this size of wire being easier to manipulate than wires of smaller or larger 

 diameter. 



In order, in the first place, to get the wire as soft as possible, it was 

 suspended from the ceiling of a room by means of a three-jaw self-centering 



1 Trans. Eoy. Soc. JBdin., Yol. xxxii. ^ Paris, 1900, vol. ii., ijp. 536-556. 



3 Phys. Math. Soc. Tokyo, Proc, 1906. 



« Scietit. Proc. Hoy. Dublin Soc, vol. xii., No. 36, pp. 480-499. 



^ For the clieniical analysis I am indebted to Mr. A. O'Farrelly, M.A., Lecturer in Organic 

 Chemistry in the Eoyal College of Science, who found the foUo^i'ing percentage composition: — 

 Ni = 98-9 ; Fe = 0-79'; SiOs = 0'13 ; Cu = 0-11 ; C = 0-02 ; Zn = a trace. 



