the Galvanic Current through Iron. 17 



numbers of § 4. The intensity of the extra currents increases 

 with the amount of the magnetizing force, at the commence- 

 ment more quickly, afterwards (*'. e. with high magnetizings) 

 more slowly than it. 



It is here presupposed that the principal current is not closed 

 till some time after the closing of the magnetizing- one. If it be 

 closed shortly after or simultaneously with that current, the 

 phenomena become very irregular. They are totally changed 

 when the principal current is closed first, and then the mag- 

 netizing one. The closing-currents are then feebler by far ; 

 but if accessible to observation, their direction is found to be 

 the opposite ; that is, they correspond to a diminution of re- 

 sistance. Sometimes a whole series of oscillating extra cur- 

 rents is observed. 



§ 6. The experiments communicated in § 4 appear to me 

 adapted to mediate between the results obtained by previous 

 observers relating to this subject. Indeed nearly all of these, 

 however divergent they may seem, reappear in my results, 

 and receive their provisional explanation by the variety of the 

 circumstances under which they were gained. Beetz found 

 under all circumstances an increase of the resistance ; but he 

 appears to have always employed very powerful magnetizing 

 forces, and to have operated only with iron and not with steel 

 rods ; and under these two conditions I also constantly ob- 

 tained positive values of 8. Stewart and Schuster observed 

 in a magnetized copper wire, when the magnetizing force was 

 great, a diminution of the resistance ; it behaved, then, like 

 my steel wires. Unfortunately, it is not stated whether the 

 wire consisted of pure (diamagnetic) copper or of copper con- 

 taining iron (paramagnetic), as commercial copper usually 

 does. Edlund and Mousson did not get any alteration of the 

 resistance by magnetizing, although the accuracy of their 

 measurements was not essentially inferior to that of Thomson's. 

 In my Tables also some are found which give for 8 the value 0. 

 Lastly, Adams published in the ( Proceedings of the Royal 

 Society'* a preliminary communication from H. Tomlinson 

 (but I have in vain sought the full paper in the i Transac- 

 tions '). According to these data, which afford extremely 

 few fixed points, in hard steel the magnetizing has for its con- 

 sequence a diminution, in iron and soft steel an increase of the 

 resistance. This is in complete accordance with my state- 

 ments, if it be admitted that the magnetization applied by 

 Tomlinson was always considerable. This is probable from 

 the enormous magnitude of the numbers which I designate 



* June 17, 1875. 

 Phil Mag. S. 5. Vol. 8. No. 46. July 1879. 



