[ 101 ] 



XJI. 



MECHANICAL STRESS AND MAGNETISATION OF IRON. 



Part T. 



BY WILLIAM BROWN, B.Sc. 



[Read Februakv 23. Ordered for Publication Makch 9. Published May 28, 1909.] 



Since the year 1837, when Professor O. Wiedemann ohserved the effects of 

 torsion on the magnetisation of iron, a good deal of work has been done on 

 the effects of mechanical stress on the magnetism of the magnetic metals, 

 especially iron and nickel. 



An excellent report of the work done up to the year 1900, with references 

 to the original papers, has been prepared by Professor H. Nagaoku,' in which 

 the theoretical and experimental results so far obtained are summed up in 

 two parallel columns containing sixteen statements. One of the columns is 

 headed — -"Deformations produced by magnetisation," and the other — " The 

 influence of mechanical stress on magnetisation." 



Of the sixteen separate statements of results, the following six bear on 

 the subject-matter of the present paper. 



1. A wire magnetised longitudinally is twisted by circular magnetism. 

 la. When a longitudinally magnetised wire is twisted, it becomes 



circularly magnetised. 



2. A wire circularly magnetised is twisted when magnetised longi- 



tudinally. 

 2a. A circularly magnetised wire becomes longitudinally magnetised 

 when twisted. 



3. The torsion produced by longitudinally magnetising a wire of iron or 



nickel when magnetised circularly, attains a maximum in feeble 

 magnetic fields. 

 3a. The transitory current due to the torsion of a wire of iron or nickel 

 magnetised longitudinally, attains a maximum in a weak magnetic 

 field. 



1 Eapports du Congres International de Physique, Paris, 1900, Yol. ii., pp. 536-656. 

 SCIENT. PROC. B.D.S. VOL. XII., NO. XII. T 



