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XLIV. A Contribution to the Theory of Magnetic Induction 

 in Iron and other Metals. — Part II. By John Buchanan, 

 D.Sc.(Lond.)*. 



IN the Phil. Mag. for March of this year there appeared a 

 paper of mine with the above title. It will be referred 

 to below as Part I. We are now in a position to discuss in 

 more detail the application of the general theory there given 

 to some of Dr. Ewing's experimental results. 



As in all such cases, the question resolves itself into the 

 operation of determining constants — in other words, of find- 

 ing the form of the graph which represents the initial con- 

 ditions, such conditions being expressed by x = Q in (11) 

 Part I. Work of this kind requires the expenditure of a 

 good deal of time, so that I am able to give here a first 

 approximation only. 



My objects in presenting these approximate results are to 

 indicate the nature of the problem involved in the applica- 

 tion of the general theory to the experimental facts, to suggest 

 the form of the solution, and to compare the values of x 

 found here with those obtained in Part I. by an entirely 

 different method. 



The methods used and the results obtained will be found, 

 I trust, of sufficient interest to justify their publication. 



Curve for Annealed Iron (cf B. fig. 1, Part I.). 



In the footnote, p. 336, Part I., I have given #=1*2 for 

 this curve, whilst the saturation intensity of magnetization 

 (c) is given as 0*84, that is 0*84 x 1700 = 1428 c.G s. units. 



These results were obtained by the determination of the 

 constants in the case where the specimen of iron was sub- 

 jected to a continuous increase of magnetizing force. 



I propose now to consider that curve of fig. 14, plate 59 

 of Dr. E wing's paper in the Phil. Trans, pt. ii. 1885, which 

 refers to the behaviour of the same specimen when the 

 magnetizing force was varied cyclically. 



This curve was subjected by me to harmonic analysis. 

 The period was taken as 1 80 ; 90 readings of I were taken off 

 the curve at equal intervals of H. By help of 4-figure mathe- 

 matical tables I get as the harmonic constituents of the curve 



1521 si n(^H-5°-0); 

 468sin(g ) H-14°-l); 

 273 sin ^ H-22°-3J. 



* Communicated by the Author. 



