194 



Mr Rudge, Experiments on the Retention 



Experiments on the retention of an electric charge by gases. 

 By W. A. Douglas Kudge, M.A., St John's College. 



[Read 27 November 1905.] 



If an ordinary vacuum tube or incandescent lamp is partially 

 coated with tinfoil, it will act as a condenser, the tinfoil acting as 

 one conductor, and the residual air in the tube as the other. 



In the following account of the experiments the apparatus 

 used will be generally referred to as the condenser. 



The experimental condenser was made by partially coating 

 a Wurtz distillation flask with tinfoil, and closing the mouth with 

 an india-rubber stopper, through which passed a short wire having 

 a knob at one end. See Fig. 1. The flask could be conveniently 



Fig. 1. 



exhausted by the side tube. When this was done, and the knob 

 brought near one of the terminals of a Wimshurst machine, the 

 condenser could be charged and discharged in the ordinary way, 

 a bright spark passing on discharge and a glow filling the tube 

 just for a moment. The air in the flask at a pressure of about 

 1 cm. acts as a conductor, so that, on bringing a wire from the 



