the Electrical Conduction produced by it. 



12; 



distances from the surface sniull compared with the diameter 

 of the radiating surface. 



The radiation passing through the aluminium produces 

 conductivity between A and B (fig. 3), and the rate of 

 leak depends on the intensity of the radiation which has 

 passed through a certain thickness of gas and the aluminium 

 foil. As the system AB is moved from the base-plate, if 

 there is a rapid absorption of the radiation in the gas, we 

 should expect the rate of leak to fall off rapidly, and this 

 is found to be the case. The following table gives the results 

 obtained for air, hydrogen, carbonic acid, and coal-gas. For 

 the first reading the distance d of the aluminium foil from the 

 base-plate was about 3*5 mm. 





Kate of leak between plate: 





Distance of Al. foil 

 from Uranium. 



Hydrogen. 



Air. 



Carbonic 

 Acid. 



Coal-gas. 



d 

 d + 1-25 mm. 

 ., + 2-5 „ 

 „ + 3-75 „ 

 , + 5 



,. + 7-5 „ 

 „ +10 

 „ +125 „ 

 „ +15 



1 



•84 

 •67 

 •53 



1 



'67 



•45 

 •31 

 •21 

 •16 



1 

 •74 

 •57 

 •41 

 •32 



1 

 •81 

 •63 

 •39 

 •22 



The rate of leak for the distance d is taken as unity in 

 each gas for the purpose of comparison. The actual rates of 

 leak between A and B for the distance d is given in the 

 following table : — 



Gas. 



JRate of leak 



in scale-divisions 



per min. 



Hydrogen 



25 



35 



28 

 18 



Coal-gas 



Air 



Carbonic acid 



13UZ 



