422 Prof. E. Wiedemann on the Behaviour of Gases 



The great differences in the behaviour of positive and nega- 

 tive electricity may perhaps be explained by assuming that 

 the propagation of negative electricity alone depends upon 

 the communication of electric polarization, whilst that of posi- 

 tive electricity is associated with a transference of free aether 

 from molecule to molecule, as indeed Yon Ettingshausen * 

 has recently concluded from the experiments of Hall f. 



We should thus have explained at once the difference in 

 potential necessary for the commencement of discharge from 

 the negative and positive electrodes. At the negative elec- 

 trode the resolution of the dielectric polarization alone is ne- 

 cessary, whilst at the positive the attraction of the material 

 molecules for the aether has also to be overcome. 



The propagation of the discharge issuing from the negative 

 electrodes obeys nearly the laws of light. From each point 

 of the electrode there apparently issues a feebly diverging 

 bundle of kathode-rays, which behaves in its further course 

 almost exactly like a beam of light, casting shadows, produ- 

 cing phosphorescent light, and so on. But we must not look 

 upon the electrode as itself the source of light, but as a sur- 

 face parallel to a wave-surface. For in the source of light 

 the displacements of the aether envelopes of the separate mole- 

 cules are still altogether without law, and take place indiffer- 

 ently in all directions. The wave itself, all of whose parts 

 vibrate isochronously, is first formed at a definite distance from 

 the electrode ; whilst at the electrode the dielectric polarization 

 possesses a perfectly definite position, and is simultaneously 

 resolved at all points. The superficial molecules of the elec- 

 trode itself do not form a wave; for the displacements do not 

 occur in them in the same manner as, for example, when the 

 kathode-rays issuing from the negative electrode produce 

 phosphorescent light when they strike the glass wall in the 

 same way as light-waves. If, for example, a part of the 

 outer wall of an exhausted glass tube be covered with a me- 

 tallic coating and this be connected with the induction-coil, 

 the inner wall of the tube at this point becomes alternately 

 negative and positive; nevertheless I have never been able 

 to observe the green light on it. Leonh. Weber J has also 

 recently employed such exterior coatings for the study of 

 Hittorf's phenomenon. 



The deviation of the positive discharge, by connecting the 

 outer surface of the tube at any point with the earth, would be 

 an effect of the altered potential produced by the altered dis- 



* Von Ettinghausen, Wien. Ber. lxxxi. March 4, 1880. 

 t Hall, Phil. Mag. [5] vol. ix. p. 225, 1880. 

 % L. Weber, Carl. Rep. xvi. p. 240, 1880. 



