On the Magnetization of Iron and Steel. 247 



In § 1 of my paper it is shown that the integral —\rndK. 

 extended over the curve C represents in absolute measure the 

 work done on the magnet during a cycle. In § § 2, 6, 7 it is 

 explained how the above phenomenon and this theorem are 

 connected with the heat produced in a mass of iron by changes 

 of magnetization, with the damping action exerted by a plate 

 of iron on a magnet swinging over the plate *, and with the 

 experiments of Christie f and Barlow \. §§3 and 4 contain 

 measurements concerning the described phenomenon for wires 

 of different dimensions, and discussions of the results obtained. 

 Lastly, in § 8 the analogy of the described phenomenon with 

 the friction of solids is pointed out. 



Poisson|| has given another theory of the damping action 

 exerted by an iron plate on a magnet swinging over it. In 

 Poisson's theory this action is made to depend upon a function 

 of time; while in my theory the damping action depends on a 

 merely statical phenomenon. In the experiments which F. 

 Himstedtlf has made to test my theory, the greatest part of 

 the damping effect is shown to depend certainly on the action 

 explained in my theory. Indeed, in these experiments, (1) the 

 logarithmic decrement of the swinging magnet was found to 

 be independent of the vibration -time, if this was altered by 

 altering the moment of inertia of the swinging system; 

 (2) about 0'84 of the observed damping action was calculated 

 from merely static experiments; and reasons are given in F. 

 Himstedt's paper that the remainder did not depend upon the 

 Poisson effect. 



In the physical laboratory of the Freiburg University an 

 experimental inquiry has been executed by L. Honig, con- 

 cerning the connexion of the described phenomenon with the 

 heat actually evolved in iron wires by changes of magnetiza- 

 tion . The results of this investigation will soon be published 

 in Wiedemann's Annalen. 



I remain, Gentlemen, 



Yours respectfully, 

 Freiburg i B., February 24, 1883. E. Waebueg. 



netic moment of an iron wire observed by Sir W. Thomson (Phil. Trans, 

 clxx. pp. 68-72, 1879) and independently by myself are connected ; pro- 

 bably also observations of E. Cohn (Wied. Ann. vi. pp. 388-392) on the 

 thermoelectric properties of stretched iron wires." 



Results similar to those obtained by me for iron wires have since been 

 found (but not yet published) in cobalt and nickel by A. Ehret. 



* Seebeck, Pogg. Ann. vii. p. 203, and xii. p. 352. 



+ Phil. Trans. 1825, part 1, pp. 347-417. 



\ Ibid. pp. 347-417. The last two points haye not been considered by 

 Mr. Ewing. 



ii Memoires de VAcademie, 1823, p. 467. 



^1 Wied. Ann. vol, xiv. p. 483. 



T2 



