88 Prof. E. Wiedemann on the 



traversed by the kathode-rays which enables us to trace the 

 course of the rays. The aether envelopes of the gas-molecules 

 upon which they strike are thrown into vibration and emit 

 light. Since the kathode-rays possess in themselves very 

 great energy, and therefore when absorbed yield up a large 

 amount of energy, it does not appear remarkable that hydrogen 

 in the kathode-rays shows the line-spectrum and not the band- 

 spectrum, that in nitrogen we have a prevailing blue colour, 

 and so on. 



With strongly decreasing pressure the brilliancy of the 

 kathode-rays decreases because the number of luminous gas- 

 particles is lessened. 



(4) We find when a negative electrode is produced, whether 

 by directly communicating negative electricity or by con- 

 necting the wall with the earth at the point in question, and 

 thus condensing positive electricity, that metallic electrodes 

 generally, and the glass wall always, become covered with a 

 luminous glow, which, upon spectroscopic examination, shows 

 the sodium-lines and the hydrogen- lines, especially the red 

 one, whilst in the kathode-rays themselves, as already men- 

 tioned, the blue part of the spectrum predominates. It is in 

 the highest degree improbable, however, that there is always 

 produced at the secondary kathodes on the way a temperature 

 so high as corresponds to the dissociation of vapour-steam. The 

 very lively aether motions produced at the point of origin of the 

 kathode-rays will no doubt here also call forth primary aether 

 motions in the solid body, which will then secondarily produce 

 dissociation and rise of temperature. Since at the electrode 

 itself the number of molecules is greater than in the tube, and 

 the wall continuously absorbs energy, the gas itself can only 

 absorb a relatively smaller amount of energy per molecule than 

 in the free gas-space; hence here also the red hydrogen-lines 

 are relatively brighter than in the kathode-rays themselves. 



(5) The phenomenon discovered by myself*, and called by 

 Golds teinf reflection of the kathode-rays, is at once accounted 

 for by the fact that they are rays of light, 



(6) The " deflection " fully examined by Goldstein % consists 

 in a bending which the kathode-rays suffer when they pass 

 near another kathode. The phenomenon is exactly similar 

 to that which occurs when a ray of light passes near a body 

 which is surrounded by an atmosphere the density of which 

 decreases from within outwardly, or which is of variable 



* Wied. Ann. x. p. 236 (1880) ; Phil. Mag. vol. x. p. 411. 

 t Wied. Ann. xv. p. 246 (1882). 



\ i Eine neue Form electrischer Abstossung/ Berlin (Springer), 1880 ; 

 Beibl. iv. p. 822 (1880). 



