176 Prof. Gr. Wiedemann on the Laws of the 



same influence the positive discharge would spread out wider 

 than the negative in the negative air, in which it is already 

 partially neutralized, must be a question for a special investi- 

 gation. 



In another place P. Riess* attempts to derive the action 

 of the electric egg from the fact that the air which surrounds 

 the electrode is charged with the electricity of the electrode 

 by the glow discharge which always precedes the explosive 

 discharge, and this air must be broken through subsequently 

 bv the explosive discharge ; therefore a discharge in a direc- 

 tion opposite to the first would be more readily conveyed 

 between the electrodes than one in the same direction. 



Since the glow discharge in rarefied air on a large surface 

 takes place most readily when the surface is negative, so in 

 the alternating discharge of the electric egg the large electrode 

 will more readily show a glow when it is negative, and will 

 therefore more easily permit the passage of the current, for 

 which it serves as a positive electrode. The last phenomenon 

 of discharge may therefore be referred to a previous contrary 

 current, and a consequent secondary charge of the air. As, 

 however, the passage of electricity between a large and a 

 small electrode in a space of rarefied air follows precisely the 

 same conditions, even when no contrary current has previously 

 passed between the electrodes, the above hypothesis cannot 

 be absolutely correct. The fact that a large negative electrode 

 becomes luminous in rarefied air more readily than a positive 

 one, also requires explanation. The experiments mentioned 

 in this and the former memoir ought to account for this, as 

 well as for the characteristics of the electric egg, even without 

 the supposition of secondary occurrences. If a series of dis- 

 charges, having passed for a length of time in a particular 

 direction through a tube, is suddenly reversed, the discharges 

 then first ensuing undoubtedly take place somewhat quicker 

 than those which follow — because the glass is still charged 

 in a manner corresponding to the direction of the first cur- 

 rent, and accelerates the speed of the opposite electricities 

 conveyed to the electrodes by the reversal of the current. 

 Soon, however, the normal charge of the glass is restored, 

 and the succession of discharges is perfectly regular. 



The question further arises, at what point the electric 

 movements of the gas molecules which advance with different 

 velocities from the two electrodes meet and the opposite elec- 

 tricities at length neutralize one another. 



* Berliner Monatsber., 6. August 1868. Pogg. Annalen, Bd. cxxxvi. S. 44. 

 Cf. Galvanismus (2), Bd. ii. S. 941. 



