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LXVII. On the Changes in the Induced Current by the employment 

 of different Resistances. By G. Magnus*. 



THE remarkably great power of hydrogen to conduct heat 

 which I had observed, induced me to compare the elec- 

 trical conducting power of this gas with that of other gases. I 

 encountered difficulties, however, which at last compelled me to 

 believe that under certain hitherto unobserved circumstances 

 opposite currents are formed, and that by means of these the 

 irregularities of the deflection of the magnetic needle which I 

 noticed were brought about. It was therefore necessary to in- 

 vestigate the conditions under which these currents were ori- 

 ginated. 



Poggendorff has shown f that if in the wire that completes the 

 ch'cuit of an induction apparatus in which there is an " electric 

 egg," and in which only currents of a given direction are circu- 

 lating, a Leyden jar be introduced, both polar wires of the 

 " electric egg " are covered with blue light. Also the magnetic 

 needle of a galvanometer placed in the current, though pre- 

 viously undergoing deflection, is now no longer turned aside, 

 from which he inferred that by the introduction of the Leyden 

 jar opposite currents were established. Since then the pre- 

 sence of blue light at the two poles of the " electric egg " has 

 almost always been looked upon as the sign of the existence of 

 opposite currents, and especially so, seeing that Riess J had even 

 before this produced these appearances by opposite currents 

 quickly following one another. It is certainly possible that blue 

 light at both poles may not in all cases be an indubitable sign of 

 the presence of opposite currents ; still it is difficult to imagine 

 that these appearances should have another cause. Nevertheless 

 I shall not examine any further into this cause. To understand 

 what follows, I emphatically remark that where the expression 

 opposite currents is used, nothing more is signified than the pre- 

 sence of negative light at both polar wires. Dr. Paalzow §, in a 

 research which appeared a short time ago "On the different 

 ways of discharging the Leyden Battery, and on the Direction 

 of Principal and Secondary Currents," used a similar pheno- 

 menon as a test. He, however, employed the so-called Geissler 

 tubes, and observed them between the poles of an active electro- 

 magnet. I have made use of short tubes, 75 to 150 millims, 

 in length, and 5 to 15 millims. in diameter, which were sealed 

 after the air that they contained had been rarefied to from 4 



* Translated from the Sitzungsberichte der Akademie der Wissen~ 

 schaften zu Berlin, June 6, 1861. 



t Poggendorff's Annalen, vol. xciv. p. 328. 



J Ibid. vol. xci. p. 291. § Ibid. vol. cxii. p. 567. 



