218 Mr Orange, On certain phenomena of the kathode region. 



various rays it is possible, nevertheless, to map out their courses 

 with considerable precision. 



Much of the work on the distribution of the kathode rays has 

 been performed by Goldstein. His paper, "Ueber den Einfluss 

 der Kathodenform auf die Vertheilung des Phosphorescenzlichtes 

 Geissler-'scher Eohren"* deals very thoroughly with the phos- 

 phorescent patterns produced on the glass walls of discharge- 

 tubes by kathode rays arising from concave kathodes of various 

 geometrical outlines. 



Somewhat related to the same subject was the work of 

 Campbell Swinton-f* on the kathode rays from concave carbon 

 kathodes. 



A much more recent paper by Goldstein J deals with the 

 phenomena of the double or sandwich kathode, while supple- 

 mentary observations have been made by Kunz§. 



The subject has also been treated in a rather different way by 

 Prof. J. J. Thomson II. 



The general method in most of this previous work seems to 

 have been to obtain phosphorescent effects and to establish the 

 paths of the rays from these. The experiments described below 

 were intended to demonstrate the paths as far as possible directly 

 by virtue of the luminosity of the rays themselves. 



The primary object of these experiments was to test the view 

 put forward by Prof. J. J. Thomson of the beams of rays obtained 

 with a double kathode composed of equilateral triangles. He 

 observed that well-marked pencils of kathode rays arose from the 

 middle points of the sides of the triangles, while minor ones 

 proceeded from the corners. His explanation IF was that the rays 

 will occur principally in the regions where the lines of force are 

 straight or nearly straight, since in such circumstances any positive 

 ions produced by the kathode rays will strike the kathode very 

 near the source of those rays, which would not be the case in 

 regions of strongly curved lines of force. 



In my first experiment I employed a double triangular kathode 

 of extremely unsymmetrical outline, the lengths of the sides of 

 the triangles being 36, 24 and 16 mm., i.e. a :h = b : c = d : 2. 

 It was thought that with this arrangement the straight lines of 

 force would occur, not at the middle points of the sides, but at 

 other points which could be determined roughly. Since, however, 

 the field is due not only to the charged kathode but also to a 

 large extent to the distribution of charge throughout the region, 



* E, Goldstein, Wied. Ann. xv. 1882, p. 254. 



t A. A. Campbell Swinton, Proc. Roij. Soc. Vol. lxi. (1897), No. 370, p. 79. 



+ E. Goldstein, Phil. Mag. March 1908, p. 372. 



§ J. Kunz, Phil. Mag. July 1908, p. 161. 



II J. J. Thomson, Phil. Mag. Oct. 1908, p. 657. 



H Ibid. p. 666. 



