184 SECONDARY ELECTROMOTIVE PHENOMENA IN 



negative by dotted lines, the resultants by continuous lines. In 

 this representation the assumption is made that positive polar- 

 isation declines more slowly in time, and negative more quickly. 

 A glance now at the figure shows that if the primary current 

 is opened at the time ^ the polarisation will always remain 

 positive. On opening it -at the time T k , if one could hit this 

 time, the polarisation would be nil for the first moment and then 

 positive. If, however, it is opened at the time t z a double action 

 follows, first negative and then positive. Further on at t 3 the 

 negative polarisation, which increases more in proportion to the 

 time of closure, has risen so high above the positive, which has re- 

 mained nearly at the same height as at first, that notwithstanding 

 the more abrupt descent of the negative curve the curves no longer 

 intersect each other, and purely negative polarisation appears. 



Besides the actions in two opposite directions which can be so 

 satisfactorily explained, there occur in the successive phases of the 

 polarisation-currents peculiarities, which, inasmuch as they do not 

 occur regularly under definite conditions, are difficult to indicate 

 with certainty. In a few cases, polarisation in opposite directions 

 occurs with a first positive and second or principal negative deflec- 

 tion. Often the polarisation increases very slowly, which probably 

 depends on the disappearance of the opposite kind. Frequently, 



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indeed, the actions are in one direction only, but double in so 

 far that the deflection first reaches a maximum then sinks to a 

 minimum, and then once again rises to a maximum which often 

 even exceeds the first. A case of the sort is seen in the preceding 

 table, with a descending current, and 14"- 754 time of closure. 

 This is explained by the circumstance that the two component 

 curves, drawn relatively to the time of opening, take such a course 

 that the one is completely above the other, but is more convex 



