126.. Prof. E. Rutherford on- Uranium Radiation and 



The results of the previous table are shown graphically in 

 fig. 4, where the ordinates represent currents and. the abscissae 



Fisr. 4. 



distances from the base-plate. It will be seen that the 

 current decreases most rapidly in carbonic acid and least in 

 hydrogen. As the distance from the base-plate increases in 

 arithmetical progression, the rate of leak diminishes approxi- 

 mately in geometrical progression. The rapid decrease of 

 the current is due to the absorption of the radiation in its 

 passage through the gas. The decrease of the current in air 

 at 190 mm. pressure is also shown in the figure. Since the 

 absorption is smaller for air at this pressure than at normal 

 pressure, the rate of leak diminishes much more slowly with 

 the distance. 



In the above experiments both the a and ft radiations 

 produce conductivity in the gas. A thin layer of uranium 

 oxide was, however, nsed, and in that case the rate of leak due 

 to the j3 radiation may be neglected in comparison with that 

 produced by the a radiation. 



The results that have been obtained on the variation of the 

 rate of leak with distance may be simply interpreted on the 

 theory of the ionization of the gas through which the radia- 

 tion passes. It is assumed that the rate of ionization is 



