Influence of the Shape of the Kathode in Geissler's Tubes. 455 



of exciting phosphorescence at their ends. They are capable 

 of being deflected ; and their ends are bent aside by a magnet 

 in the same direction as the ends of the kathode-rays would 

 be which radiated from the reflecting surface to the points 

 reached by the reflected rays. 



LI. On the Influence of the Shape of the Kathode on the Dis- 

 tribution of the Phosphorescent Light in Geisslers Tubes. 

 By Dr. E. Goldstein*. 



[Plate VLT. figs. 9-35.] 



CYLINDRICAL wires cut off at right angles have been 

 almost exclusively employed as kathodes in systematic 

 investigations on the discharge of the induction-coil in rarefied 

 gases, or, in particular cases, spherical electrodes or plane 

 circular disks. Kathode-surfaces, which can be divided into 

 two halves of similar shape by an infinite number of cuts, do 

 not give rise to a class of phenomena which I have observed 

 with kathodes of regular surface, in which nevertheless there 

 is no axis of symmetry corresponding to an infinite number 

 of equivalent sections. 



We are concerned with extremely regular figures, in which 

 the phosphorescent light of the walls illuminated by the 

 raysfrom those kathodes arranges itself, which, however, are for 

 the most part altogether unlike the shape of the kathode itself. 

 Reserving a detailed description, I may here give the general 

 characters of the most important types of these figures f. 



Kathodes of concave spherical form were first examined 

 constructed of thin soft iron, which was first of all stamped 

 and then ground into the desired form. 



The kathodes were soldered at the middle points of their 

 convex sides to wires which conveyed the current, and which 

 were insulated by being covered with glass thermometer-tubing 

 between their junction to the kathode and the point at which 

 they entered the vessel. 



The discharge- tubes were glass bulbs of 4 to 5 centim. 

 radius; the axis of the spherical concave mirror which formed 

 the kathode was placed in a diameter of the bulb. The dis- 

 tance of the kathode from the wall, measured along this dia- 

 meter from the centre of the mirror, could be varied ; in the 



* Monatsber. der Konigl. Akademie der Wissenschaften zu Berlin, July 

 1881 Translated from a separate impression communicated by the Author. 



t A preliminary notice appeared iu the Wien. Ahad. Anzeiger of the 

 13th Jan. 1882. The phenomenon of figures in phosphorescent light dis- 

 similar from the kathode was described by me for the case of a kathode 

 of cylindrical curvature so long ago as 1876 ( Wien. Sitzimqsber. lxxiv. 

 [2] p. 465). 



