1908] on the Garners of Positive Electricity. 181 



that the initial velocity was less, for before reaching the screen the 

 rays have had to make a long journey through the gas, and if the 

 pressure is high, they will in their journey lose more of their velocity 

 than when the pressure is low. 



To test whether or not the velocity of the rays was due to the 

 electric field, I tried the following experiments : — 



In the first experiment, a piece of wire gauze was placed about 

 2 mm. in front of the perforated electrode of the tube represented 

 in Fig. 2 and well insulated from it ; the gauze was used as the 

 cathode, and measurements of the velocity of the particles were made 



(1) when the perforated electrode was connected with the gauze, 



(2) when it was connected with the anode. In the second case, a 

 particle if it retained its charge during the whole of its path, would 

 in its journey between the gauze and the perforated electrode be at 

 least as much retarded as it had been accelerated before reaching 

 the gauze, and any velocity it possessed after passing through the 

 perforated electrode must have been acquired from sources inde- 

 pendent of the electric field ; while in the first case its velocity 

 would be measured by the electric field in the tube. On trying the 

 experiment, it was found that though the Canalstrahlen were not 

 nearly as bright in the second case as in the first, they were still 

 quite perceptible, and that the velocity of those which got through 

 was the same as the velocity of those reaching the screen in the first 

 case. The fact that a large proportion of the rays are stopped by 

 connecting the perforated electrode with the anode, while those which 

 get through are not affected, shows that the velocity of the majority 

 of them is not great enough to travel against the potential- difference 

 between the electrodes ; while the fact that some get through without 

 diminution of velocity, indicates that when they are passing between 

 the gauze and the perforated electrode, they are for the moment 

 electrically neutral and without charge, and that they re-acquire, by 

 losing a corpuscle, a positive charge after passing through the open- 

 ing in the electrode by collision with the molecules of the gas. The 

 following experiment shows in perhaps a simpler way than the pre- 

 ceding one that some of the Canalstrahlen are uncharged during a 

 portion of their path. The perforated cathode (Fig. 5) was wedge- 

 shaped, the angle of the wedge being about 27°, the diameter of the 

 cathode was 2 cm., the aperture through which the Canalstrahlen 

 passed was about 5 mm. from the sharp end, the length of the path 

 of the rays from one side of the cathode to another was about 2 • 5 

 mm. A flat piece of wire gauze was fixed parallel to the upper face 

 of the cathode (the face most remote from the anode), and insulated 

 from it : the distance of the gauze from the cathode was about 3 mm. 

 The Canalstrahlen travel at right angles to the lower face A B of the 

 cathode. If the wire gauze is connected with the anode, and if the 

 particles in the Canalstrahlen are charged, they will after passing 

 through the cathode be acted on by a force which has a component at 



