the Galvanic Current through Iron. 151 



if it alter the resistance at all, shall augment or diminish it 

 according as the direction of the artificial is the same as or 

 opposite to that of the natural circular magnetization, and 

 according to their intensities. I am not aware of any expe- 

 riment on this point. On the other hand, Sir W. Thomson * 

 conducted the current through a square iron plate in a direc- 

 tion inclined to the direction of "the magnetization. The poles 

 of the electromagnet were situated at two opposite sides of the 

 square, the electrodes of the principal current in two oppo- 

 site angles. Of the individual current-threads into which the 

 plate under these circumstances divides, Thomson investigated 

 the two meeting at the margin, each of which consists of two 

 consecutive edges, ABC and ADC (fig. 4). The result of the 

 experiment was, that the magnetization of the level-line D B 

 was shifted into the position De, and consequently the resist- 

 ance along A B was less than that along A D, and the resist- 

 ance along D C was less than that along B C. Beetz and 

 others have pointed out that even the mechanical pull con- 

 nected with the magnetizing would by itself alone have neces- 

 sitated this result. I think I must concur in this explanation; 

 I will, however, show that my theory is not inconsistent with 

 Thomson's observation, that, under some circumstances, it 

 requires the latter, and that these circumstances were not pre- 

 sent in the corresponding experiment made by Beetz f (which 

 had a negative result). 



Along the line AB, in Thomson's experiment, the directing 

 force of the electromagnet will disturb the circular magneti- 

 zation more or less, according to its intensity in comparison 

 with that of the current-thread, and change it into a trans- 

 verse magnetizing, in which all the molecular north poles 

 point to the same side of the space. At the same time the 

 resistance in certain lines of the current-thread, namely in 

 those in which both the magnetizing forces have the same 

 direction or make with one another an angle of 180°, will be 

 but slightly changed ; in the rest it will be generally dimi- 

 nished. Thus the total resistance will either be lessened or, 

 if the electromagnet is powerful, somewhat but not much in- 

 creased. But just in this latter case the resistance of the cur- 

 rent-thread B C must very considerably increase ; for here 

 the electromagnet nullifies the circular magnetizing and pro- 

 duces a powerful longitudinal magnetization. From this, it 

 is true, nothing can be inferred as to how the total resistance 

 of A B C varies ; but just as little can be inferred from Thom- 

 son's experiments. It merely follows that the whole or the 

 greatest portion of any decrease of the resistance, but only 

 * Loc. cit. p. 741. t Loo. cit. p. 206, 



M2 



