450 Dr. E. Goldstein on the 



ments which have led me to reject this assumption were sug- 

 gested by an observation made by Prof. B.Wiedemann*. 



Prof. Wiedemann, in using a tube of the form of fig. 1 

 (Plate VII.), where the disk k at right angles to the axis of 

 the vessel C forms the kathode, not only observed green phos- 

 phorescence such as produced by the kathode-rays on the 

 sides of the tube up to the point x which could be reached by 

 straight lines from k, but saw also a feeble illumination of the 

 tube r beyond the bend, and a brighter phosphorescent sur- 

 face F on the wall C opposite the mouth of the tube r. The 

 motions of the small surface F under the influence of the 

 magnet showed that it was produced directly by electrical 

 rays, and not simply by optical rays possibly reflected at the 

 glass. 



Prof. Wiedemann is disposed to explain the appearance as 

 one of the phenomena of deflection discovered by met, assu- 

 ming that the glass wall at x becomes charged and acts as a 

 weak kathode, causing the deviation of the pencil of rays 

 passing by it out of the direction at right angles to the plane 

 of k, into the direction xF. 

 • This explanation seemed improbable to me for two reasons : — 



(1) Because the surface F is always much more feebly 

 illuminated than would have been the case if the phospho- 

 rescence had been exerted by the direct kathode-rays pene- 

 trating to C. In order to make the comparison, the kathode- 

 rays may be so curved by the influence of a weak magnet as 

 to pass the bend ./•. The comparison may be more certainly 

 made without the use of a magnet in a vessel of the form 

 shown in fig. 2, where two paths are offered to the kathode- 

 rays — on the one side the path as in fig. 1 through the bent 

 tube r i\, and on the other side the path through the equally 

 long straight tube r 2 at right angles to k. 



(2) Because the surface F totally disappears if the tube r r } 

 has a second bend in it, in whatever direction this second 

 bend is made. This would not happen with the phenomena 

 of deflection, which I have examined, where a ray may be bent 

 any number of times. 



If now the rays which produce the surface F are not direct 

 rays from the kathode k, then we may suppose either (a) that 

 the portions of the tube about x, upon which the rays from the 



called reflex currents in the system of tubes, partly phosphorescence pro- 

 duced by direct kathode-rays, which Herr Puluj unintentionally produced 

 by touching the glass with the finger in order to concentrate the light. 



* E.Wiedemann, Wied. Ann. xi. p. 236; Phil. Mag. [5] x. 



t Goldstein, Monatsber. d. Konigl. Akad. der Wtss. 1870. p. 286 ; Phil. 

 Mag. [5] iv. Also • A new Form of Electrical Repulsion ' (Berlin, 1880). 



