Intelligence and Miscellaneous Articles. ' 319 



(2) But at this moment the induced current is not terminated ; 

 it still increases, then diminishes pretty rapidly, and continues for a 

 certain time, becoming very weak. 



(3) The total duration of the induced current is always appreciable. 

 In some cases I have observed a feeble current as much as -^wu of a 

 second after the primary current was closed ; and it is probable that it 

 lasts even longer. 



If we wish to represent graphically the induced current, taking 

 the times for abscissae and the corresponding intensities for ordinates, 

 we have a curve formed, for times less than 5 ] of a second, of a 

 straight line almost perpendicular to the axis of the abscissae, which 

 curves while still ascending, soon attains a maximum, then rapidly 

 descends, and, after bending indefinitely, approaches the axis of the 

 abscissae without its being possible to fix exactly the point at which 

 it becomes merged in this axis. In any case this point corresponds 

 to an appreciable time. — Comptes Rendus, July 29, 1867. 



ON THE PASSAGE OF ELECTRICAL CURRENTS THROUGH 

 INCANDESCENT GASES. BY M. E. BECQUEREL. 



M. E. Bouchotte has recently observed the interesting fact that 

 when a voltameter containing acidulated water is introduced into 

 the circuit of a magneto-electrical machine which gives two series 

 of alternating currents, one current only circulates, or rather only the 

 currents which are in one direction predominate. To obtain this 

 result, it is sufficient if one of the electrodes be merely a fine platinum 

 wire just dipping into acidulated water, so as to be surrounded by a 

 luminous sheath ; this electrode is positive, and the currents which 

 correspond to this electrical arrangement are the only ones which 

 can be perceived. 



Having witnessed these effects, I thought it was possible to ac- 

 count for them on the supposition of the unequal electrical conduc- 

 tivity of vapours and incandescent gases, according to the relative 

 magnitude of the electrodes and according to the direction of the 

 currents. I observed, in fact, in 1853 *, that, starting from a red heat, 

 gases become conductors of electricity, and that, in the case of air, 

 when I used as electrodes a platinum tube and a platinum wire 

 stretched along the axis of the tube, and when the electrical tension 

 was equal, the conductivity was greater when the central wire was posi- 

 tive than when it was negative. The luminous sheath in the above 

 experiments, being formed of incandescent gaseous matters, serves as 

 conductor, the surrounding liquid and the central wire forming the 

 two electrodes. 



With acidulated water the positive wire should give rise to the 

 maximum conductivity, since one series of currents quite preponde- 

 rates over the other. 



If, as I imagine, the phenomenon may thus be explained, to ac- 



* Annates de Chimie et de Physique, vol. xxxix. p. 371. 



