468 Intelligence and Miscellaneous Articles. 



These experiments show with certainty, since the resistance in the 

 induced circuit is in all cases the same, that the electromotive force 

 of the induced current is, in the widest sense of the word, entirely inde- 

 pendent of the nature of the induced conductor. The induction in 

 Series I. and IV. is approximately equal, in Series II. approximately 

 twice as great, and in Series III. approximately null. That these 

 relations should be quite exact could not be expected, since induction 

 takes place on other parts of the conduction besides the coils, and 

 these parts change their positions somewhat during the arrangement 

 of the experiments, and, lastly, the convolutions cannot be exactly 

 limited to six complete turns. 



After each alteration of the direction of the current in the electro- 

 magnet, the first closing regularly produces an uncommonly strong 

 induction-current (the corresponding numbers are marked with * 

 and are not taken into account in calculating the mean) . This phe- 

 nomenon doubtless has its origin in the fact that the electromagnet, 

 after the opening of the current, retains a high degree of permanent 

 magnetism ; so that in altering the direction of the current there is 

 not only a magnetization, but also an inversion of the poles, which 

 must, of course, produce a more powerful induction. Inasmuch as 

 the latter amounts to more than double the ordinary one, it follows 

 that the magnet on opening retains more than a third of its mag- 

 netism. Moreover it is observed that in by far the most numerous 

 cases the induction-current on closing is a little stronger than that 

 on opening, and that the intensity of the former is subject to some- 

 what stronger variations. This also can be readily explained : on 

 opening, the magnet always loses the same quantity of magnetism ; 

 this sudden decrease is followed by a further slower one. The in- 

 crease of magnetism at the moment of closing will therefore always 

 be somewhat greater than the decrease at* the moment of opening, 

 and will be greater the longer the pause between two experiments. 



Exactly the same phenomena were observed in the two other 

 series of experiments. In one the electromagnet was again used as 

 inductor ; between its poles, however, an iron cylinder 149 mil- 

 lims. in length and 16 millims. in diameter was inserted. This was 

 surrounded by a glass spiral of fourteen turns, width of coil 30 mil- 

 lims., filled with solution of zinc sulphate. In the other I used an in- 

 ductor, to be described elsewhere, which I have constructed for nerve 

 induction, and which is calculated for very short induced conductors ; 

 in this case a simple straight glass tube or a metal wire was used 

 for induction. — Poggendorff's Annalen, No. 4, 1871. 



Zurich, April 1, 1871. 





