Cathode and Lenard Rays. 



229' 



The wide side tube B is to enable the screen S to be pulled aside 

 entirely out of the path of the cathode rays whenever it is desired 

 to do so. The screen car easily be moved about by the magnet with- 

 out disturbing the tube which is kept sealed on to the exhausting 

 pump. 



When the tube has been exhausted until the cathode rays are well 

 developed, the screen is pulled into the side tube B, the cylinder b is 

 connected to the electrometer, and the coil turned on. The electro- 

 meter shows a negative deflection, which rises rapidly to a point at 

 which it remains constant. The passage of the discharge inside the 

 tube breaks down to some extent the insulation between the 

 cylinders a and b, and as the negative potential of b increases the 

 rate of flow of negatively charged particles into it will diminish, unbil 

 a state is reached at which b is losing charge to a at the same rate 

 at which it is receiving charge by the flow into it of the charged 

 particles, and at this point the potential of b remains constant. 



In one experiment the deflection rose to 175 scale divisions, which 

 showed that a capacity of about 30C C.Gr.S. units had been raised to a 

 potential of 87 volts. 



Everything else remaining the same, an electromagnet is placed 

 with its poles on opposite sides of the tube between the cathode C 

 and the cylinder a ; when the magnet is on and the cathode rays 

 deflected off the opening c, the cylinder b receives scarcely any charge, 

 showing that the negative deflection previously observed is really 

 due to the charge carried by the negative rays. 



The screen S is now pulled from the side tube B, and placed in the 

 path of the negative rays. 



When the coil is turned on, a negative charge, smaller than pre- 

 viously, is still obtained in the cylinder b, and this charge is again 

 not observed when the magnet is placed so as to deflect the rays 

 off the screen, or so as to deflect the secondary rays from the screen 

 off the opening c. 



The screen was moved along the tube and the deflection measured 

 in different positions with the following result. 



The length of the tube from the cathode C to the cylinder a was 



12 cms. 



Distance of the aluminium 

 screen from a. 



Negative 

 deflection. 



1^ cm. 



30 

 62 

 142 

 150 

 147 

 175 



With screen in side tube B 



These numbers show that with the screen 6 cm. from a, the 



