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XI. MiKjiu-tic Qualities of Nickel. 



/t i/ J. A. Ewivo, F.R.S., Professor of Engineering in University College, Dundee, 



and G. C. COWAN. 



Received April 26, Read May 17, 1888. 



[PLATES 15, 16.] 



ALTHOUGH determinations of the magnetic permeability of nickel have been made by 

 ROWLAND and others,* there appears to be no published investigation of the effect of 

 cyclic magnetising processes. The study of such processes is interesting not only in 

 its direct bearing on the relation of magnetisation to magnetising force, but indirectly 

 as yielding data from which one may calculate the dissipation of energy that occurs in 

 reversal or other variation of magnetism, in consequence of hysteresis in the relation 

 of magnetisation to magnetising force. Cyclic processes have been very fully 

 examined for various kinds of iron and steel,t and one object of the following 

 experiments was to obtain information of the same kind with regard to nickel. 

 Another object was to examine the effects of longitudinal stress on the magnetisation 

 of this metal in the same manner as they had been examined in iron by one of the 

 writers. J Sir WILLIAM THOMSON'S early results in this subject had shown that, when 

 subjected to longitudinal pull, nickel undergoes much change of magnetism, of a kind 

 opposite to that which ordinarily occurs in iron, and it seemed that a fuller 

 investigation of the effects of stress might be useful. 



The experiments, with the exception of one group described at the end of this 

 paper, were made with specimens of nickel wire supplied by Messrs. JOHNSON and 

 MATTHEY. The wire was O'OGS cm. in diameter, and was supplied in what appeared 

 to be a hard-drawn state, in which its magnetic susceptibility was decidedly less than 

 when the wire was annealed. Its magnetic quality was examined both when in this 

 hard-drawn state and after annealing. The direct magnetometric method was 

 employed, in the same manner as in the experiments on iron referred to above. || A 



* ROWLAND, ' Phil. Mag.,' Aug., 1873, and Nov., 1874 ; H. MEYER, ' WIEDEMANN, Annalen,' vol. 18, 

 p. 251. 



f EWINO, ' Phil. Trans.,' 1885, p. 523; HOPKINSON, ibid., p. 455. 



J EWINO, lof. cit., 69-113. 



Sir W. THOMSON, ' Phil. Trans.,' May, 1878 ; or ' Reprint of Papers,' vol. 2, p. 382. 



|| EWINO, loc. cit., 18. 



30.10.88 



