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XXXV. On Effects of Retentiveness in the Magnetization of 

 Iron and Steel. 



To the Editors of the Philosophical Magazine and Journal. 



Gentlemen, 



I BEG leave to forward to you for insertion in jour valu- 

 able Journal the following note. 



In the Proceedings of the Royal Society, vol. xxxiv. no. 220, 

 p. 39, there may be found a preliminary notice by Mr. J. A. 

 Ewing, communicated by Sir W. Thomson, received May 6, 

 1882 entitled, " On Effects of Retentiveness in the Magnetiza- 

 tion of Iron and Steel," the first part of which is very closely 

 related to a paper published by myself, Dec. 6, 1880, in the 

 Freiburger Berichte, vol. viii., and reprinted in Wiedemann's 

 Annalen, vol. xiii. pp. 141-164 (1881). In this paper the 

 fundamental fact redescribed by Mr. Ewing was described by 

 me a year before as follows : — 



"A permanent moment ra may have been produced in an 

 iron wire by the action of a longitudinal magnetizing force K : . 

 Next let the wire be subjected to magnetizing forces which 

 first increase continuously from to Kj and then decrease con- 

 tinuously from Ki to ; then, for the same magnetizing force 

 K, the magnetic moment of the wire will be found greater 

 when K is increasing than when it is decreasing. After some 

 repetitions of the operation the wire will be found in a sta- 

 tionary state, in which for K = it always has the same 

 moment m and for K = K X the same moment m + mi. If, 

 therefore, the wire being in 

 this condition, its moment is 

 represented graphically as a 

 function of the magnetizing 

 force K, a closed curve C will 

 be got as represented in the 

 figure, in which the ascending 

 and the descending branch are 

 marked by arrows; except 

 the minimum (0) and maxi- 

 mum (K x ) value of K, two 

 values of m corespond to every 

 value of K"*. 



* Observations included in the above statement are to be ioimd in a 

 paper by Fromme (Wied. Ann. iv. pp. 102-105, 1878) ; but the statement 

 is not derived from the observations, and their bearing on other pheno- 

 mena is not recognized. 



In a footnote of my paper the following remark may be found : — " With 

 this fact certain phenomena concerning the effect of torsion on the mag- 



