Passage of Electricity through Gases. 175 



discharge, consequent upon the greater charge which has 

 been proved by experiment to be necessary to the existence 

 of the former. 



In explanation of this circumstance the hypothesis was 

 there advanced of the unequal attraction of the two electri- 

 cities by the electrodes, which, at least so long as we are 

 obliged to retain our present conceptions of the nature of 

 electricity, agrees with the theory which we have formed of 

 the electromotive action of two metals on one another. 



As in my former memoir I did not dwell on the explanation 

 given by other physicists of these phenomena and of others 

 nearly connected with them, I will venture to touch upon 

 them again briefly here. 



In his very interesting experiments on Lichtenberg's figures, 

 Herr von Bezold* advances the hypothesis, that when they are 

 exhibited in the positive terminal a movement takes place 

 towards the conductor, when at the negative a movement 

 towards the periphery. The same circumstance does not seem 

 to occur in gas-discharges. If with increased pressure tuft- 

 shaped metal-discharges accompany the gas-discharge at the 

 positive electrode, the glowing portions of the metal must se- 

 parate themselves from the electrode and move away from it. 



In the same way, in Geissler tubes a gradual convey- 

 ance of the metal from the negative electrode to the sur- 

 rounding glass will be observed. Both phenomena, however, 

 point to a continuous movement from the electrodes of mole- 

 cules participating in the discharge, and cannot well be 

 explained by any kind of absorption at the positive electrode. 



According to P. Biess f , the difference between the positive 

 and negative discharge would be much more easily realized if 

 we supposed that the current of air which always accompanies 

 the spark of the electrode and passes by the moistened elec- 

 trode, by some kind of friction with the dry air makes the 

 latter negatively electric. 



According to the analogy of Lulliu's experiments and 

 electric dust figures, the positive electricity would subse- 

 quently be able to spread out wider in the negative space. 

 Setting aside the fact that the differences of the gas-discharges 

 at the two electrodes appear also in the most carefully dried 

 space, the positive electrode would, contrary to the result of 

 experiment, obviously require for the discharge, according to 

 this hypothesis, a lesser tension than the negative, since the 

 negative electricity of the air already exercises an influence 

 on the positive electricity of the electrode. Whether under the 



* Cf. Gahanismus, Bd. ii. S. 936. 

 t Beibungselectricitat, Bd. ii. S. 751. 



