[ m ] 



XXXIII. On the Electric Discharge in Rarefied Gases. — 

 Part II. On Luminous Phenomena in Gases caused by Elec- 

 tricity. By Dr. Eugen Goldstein*. 



[Concluded from p. 190.] 

 On a new Phosphorescent Action of the Electric Discharge. 



THE phosphorescence caused by the kathode-rays has been 

 hitherto the only example of the excitation of luminosity 

 on solid surfaces caused by an infinitely thin layer of the dis- 

 charge; and therefore . forming well-defined images. The 

 images are the section of the bundle of electric rays by the 

 wall of the tube. 



I have succeeded during the last year in discovering two 

 other modes of exciting such phosphorescence, and of uniting 

 previous observations into a more extended and consistent 

 research, whose results are of universal applicability. 



The first of these new methods of producing phosphorescence 

 occurs equally with pressures at which the kathode-rays excite 

 the previously-known phosphorescence and with pressures 

 1000 times greater — equally at atmospheric pressure and 

 when the pressure is -jho millim. This mode of phospho- 

 rescence may be observed by surrouuding one electrode of a 

 vacuum-tube with a phosphorescent powder, which fills the 

 space between the electrode and the tube and also reaches 

 beyond the free end of the electrode. If, then, while both 

 electrodes are in connexion with the induction-coil, the outer 

 surface of the glass in the neighbourhood of the powder be 

 touched with a conductor, star-like discharges pass from the 

 conducting body to the surface of the glass, similar to those 

 observed, in producing Lichtenberg's figures in the dark, on 

 the non-conducting plate to which the point conveying the 

 electricity is opposed. 



Besides these exterior discharges, there are also others be- 

 tween the inner wall and the surface of the mass of powder in 

 contact with it in the neighbourhood of the point touched. 

 These discharges also are branched; but in general they show 

 a much richer ramification and more beautiful dendritic forms. 



Now these interior discharges cause phosphorescence in the 

 surface of the mass of powder ; but this phosphorescence is 

 not equally distributed over the surface, but forms a pattern 

 of surprising delicacy, in which are seen accurate reproduc- 



* Translated from a separate impression, communicated by the Author, 

 from the Monatsberichte der koniglichen Akademie der Wissenschaften zu 

 Berlin, January 1880. 



