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LI. Intelligence and Miscellaneous Articles. 



A STUDY OF UNIPOLAR INDUCTION. 

 BY PROF. DR. ERNST LECHER. 



r PHE first part contains historical and general observations, and 

 -*- shows that neither previous experiments nor the more recent 

 modifications can settle this question. It appears that the Biot- 

 Savart law, of the action of a rectilinear conductor on a magnetic 

 pole, is not in harmony with experimental facts. 



The second part contains a condensed account of the experi- 

 ment of an electrometric proof of electrostatic charges of a rota- 

 ting magnet. The author does not consider these experiments to 

 be free from objection. 



The third part contains the experimentum cruris, and the decision 

 of the question raised. A magnet is divided by an equatorial 

 section in two parts, each of which can rotate separately. By 

 means of suitable spring contacts it is possible to obtain from the 

 two ends of the magnet an induction current which cannot pos- 

 sibly be due to a cutting of the rotating lines of force in the short 

 fixed spring contacts. The current is easily explained if we adopt 

 the view of Faraday, which, however, he afterwards abandoned, 

 that the rotating magnet cuts its own fixed lines of force, and 

 thus has an electromotive action. — Wiener Berichte, July 12, 

 1894. 



ON THE CIRCULAR MAGNETIZATION OF IRON WIRES. 

 BY PROF. DR. IGN. KLEMENCIC. 



The author investigated, in wires of soft and hard iron and of 

 Bessemer steel, the extra currents which are formed on passing a 

 current owing to circular magnetization. From the extra currents 

 the susceptibility in a circular direction may be calculated by a 

 formula of Kirchhoff. The susceptibility in an axial direction for 

 different field-strengths was determined. The experiments showed 

 that qualitatively the course of the susceptibility in both directions 

 is pretty much the same. Quantitatively, however, the following 

 difference is to be observed. With soft-annealed iron the sus- 

 ceptibility about the axis is less than in the direction of the axis. 

 If the iron wire is hardened by a stress, the susceptibility in a 

 longitudinal direction diminishes more rapidly than in the circular, 

 and the behaviour observed for soft iron may even be reversed. 



Simultaneous experiments on remanent magnetism gave greater 

 values for this with circular than with axial magnetization, especially 

 in hard iron and steel. Repeated demagnetization with greater 

 field-strengths increases the susceptibility for weaker fields, even 

 with circular magnetization. — Wiener Berichte, July 5, 1894. 



