CATHODE RAYS AND KONTGEN RAYS. 275 



the sunie path ;i.s Ix'fore hctwccii the positive electroch' andtiie cathode. 

 The priiK'ipal flow has been joined ])y a secondary one, fi'oni all points 

 of the tul)e the positive currents are directed toward the cathode, 

 and o-o to reenforce the principal current. These positive charges 

 which descend from all points of the periphery form the counterpart 

 of the negative* charges, which can be seen fixed on the cathode rays. 

 Their existence, their development, their circulation, result in conse- 

 quence from the existence, the development, and the inverse circula- 

 tion of the negative electricity that carries with it the cathode ray. 



Such is the cathode afflux; it is composed of the current directed 

 toward th(> positi\e electrode and of secondary currents directed from 

 all parts of the recipient toward the cathode. M. Villard has made it 

 very plain that all these obscure or dim emanations are united in the 

 axis of the bulb to the principal flow. 



This cathode afflux has besides the character and the properties that 

 physicists and chemists attribute to the electric current. It touches 

 directly the cathodt\ If it happens that this negative electrode — 

 which we may suppose to consist of a small, circular, metallic disk — 

 is perforated with a hole, a portion of the cathode afflux crosses this 

 opening and pursues its journey beyond, after being discharged in 

 passing. This neutral electrical current, these discharged rays, form 

 the Canalstrahlen studied by Goldstein. 



All these details with relation to the currents which flow toward the 

 cathode indicate the care with which physicists have studied the sub- 

 ject, so that none of the phenomena which take place in Crookes's tube 

 may escape them. It might be said, however, that they are foreign 

 to our principal subject, which is the cathode emission. The afflux 

 which we have just seen reach the cathode is in fact perfectly distinct 

 in ever}' respect from the cathode radiation which follows it and which 

 alone interests us. The latter is formed of a pencil of rays perpen- 

 dicular to the surface of the cathode. It is in the present case a cylin- 

 drical pencil having for a base the circular disk; it traverses the tube 

 in a perfectly straight line without being disturbed by the rays flow- 

 ing toward the cathode in an opposite direction, of which we have just 

 been speaking; it passes by them and through them unchecked. 



This new pencil implanted normally on the cathode is not luminous. 

 It is not directly visible; it forms a dark spot in the Crookes tube. 

 It would entirely escape observation if it did not excite a peculiar 

 fluorescence opposite to the cathode at the points where it meets the 

 sides of the tube. The material of the glass becomes illuminated at 

 these points and presents a luminous brilliant spot of a green color. 

 Crookes had the idea to arrange in the interior of the tube, in the path 

 of this pencil between the cathode and the wall, a variety of opacjue 

 bodies, as, for example, a cross of aluminum. He then saw outlined 



