Rays of Positive Electricity. 



363 



Fisr. 3. 



+ A 



got negatively charged by the adhesion o£ corpuscles. The 

 strong electric field near the cathode would shoot these away 

 from it, and they might in their journey through the tube 

 lose by collision with the gas not only the corpuscles they had 

 acquired, but also an additional one, and thus become posi- 

 tively charged. Another way of explaining these rays is to 

 regard the gas traversed by the positive particles moving 

 rapidly towards the cathode as being thrown into a condition 

 analogous to that of a radioactive substance and shooting out 

 with great velocity positively electrified particles (corre- 

 sponding to the a particles), as well as corpuscles (cor- 

 responding to the /3 particles). If this were the case, the 

 positive particles might be expected to be shot out in all 

 directions; while on the other view they would tend to follow 

 the lines*o£ force in the tube and be mainly right in front 

 of the cathode. 



To test this point the following arrangement was used. The 

 cathode k (fig. 3) was an aluminium disk with a hole at the 

 centre through which the Canalstrahlen passed ; after passing 



through the tube these rays fell 

 on a copper plate c rigidly attached 

 by an arm to the cathode but insu- 

 lated from it. The cathode floated 

 I ] on the mercury in a barometer- 



column, and by raising or lowering 

 the level of the mercury different 

 regions near the cathode could be 

 brought opposite to the end of the 

 side-tube T; at the mouth of this 

 tube there was an insulated metal 

 plug with a hole bored through it. 

 The tube passed between the poles 

 of a powerful electromagnet of the 

 ( ) Du Bois type ; a willemite screen 



J ( was fastened to the end of the tube: 



/ \ the anode was at A. Starting with 



gn the cathode in such a position that 



the axis of the hole in the plug- 

 passed through /, the luminosity 

 . produced by the positive rays above 



\~~ I the cathode, it was found that rays 



^B of positive electricity passed down 



the side-tube ; gradually raising 



the cathode, these rays remained 



PP until the plane of the cathode just 



got above the opening in the 



plug, when they disappeared. On raising the cathode still 



