162 Mr Radge, On the Difference of Potential, etc. 



The following conclusions may be drawn from the experi- 

 ments : — 



(1) The presence of a perforated disc in a vacuum tube 

 increases the resistance of the tube in the electrical discharge. 



(2) The increase in resistance is inversely proportional to the 

 area of the aperture of the disc. 



(3) The increase in resistance depends upon the position 

 occupied by the disc, the maximum effect being produced at a short 

 distance from the cathode. 



(4) The increase in resistance depends upon the nature of the 

 metal forming the disc, the lower the atomic weight the greater 

 the increase. 



My very best thanks are due to Professor J. J. Thomson for 

 the kindly advice he has given me during the course of the 

 experiments. 



