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XXIV. On the Magnetism of Steel Bars. By Dr. Carl 

 Fromme, Instructor in Physics at the University of Gotting en* . 



§ 1. rTIHE present memoir was suggested by a prize-theme 

 J- set by the Philosophic Faculty at Gottingen in the 

 summer of 1873, which demanded " a closer investigation of 

 the temporary portion of the magnetism of a steel bar with 

 various intensities of the permanent part, and under the action 

 of various separating forces." This problem touches a still 

 rather obscure department of physics. 



The magnetization-relations of soft iron have, in the last 

 three decades, been so profoundly investigated by numerous 

 observers, that, it might be thought, much more than a finish- 

 ing-off of the building can hardly remain for the next period. 

 But if we consider how long it took to attain clearness in 

 regard to soft iron, so easy to manage in comparison with 

 steel, it cannot be surprising that the researches hitherto car- 

 ried on concerning the latter are far from having brought the 

 desirable, or even the attainable perspicuity in the comprehen- 

 sion of its magnetization. 



The causes of the difficulties presented by steel to the explo- 

 ration of its magnetic properties are, as is well known, the fol- 

 lowing. In the first place, there is the residual magnetism 

 which appears after the action of the magnetizing force |. 

 Again, the individual varieties of steel behave very dissimi- 

 larly ; and this gives rise to a further complication. Besides, 

 steel can be used in the soft, in the hardened state, and hard- 

 ened in different degrees ; and accordingly the same sort can 

 be subjected to examination under different conditions. 



An examination of the magnetic differences resulting from 

 the specific nature of the various kinds of steel could, in our 

 ignorance of the molecular constitution of steel, afford us little 

 enlightenment; and, moreover, on this point there exist a 

 whole series of works, to add to which would appear, for the 

 present, hardly advisable. With respect to the influence of 

 hardening, I have, at least so far, disregarded it. 



Finally, the complication resulting from the appearance of 

 residual magnetism I have endeavoured to reduce to its least 

 measure, by employing only such magnetizing forces as tended 

 to preserve the polarity produced by the permanent magnetism 

 once present. 



I have therefore at present worked under the simplest condi- 



* Translated from a separate impression, communicated by the Author, 

 from PoggendorfPs Annalen, Erganzungsband vii. pp. 390-430. 



t On this vide Wiedemann, Galvanismus, vol. ii. § 314. IV. (2nd ed.). 



