532 Miss Jadwiga Szmidt on Distribution of Energy in 



brass box (10 x 10 X 10 cm.) lined with cardboard and con- 

 taining two parallel aluminium electrodes 8 cm. apart. One 

 of these, cc (fig. 2), was raised to a potential high enough 

 to ensure saturation, the other, dd, was connected to the 

 Wilson- Kaye electroscope, d d was surrounded by a guard- 

 ring, divided from it by an air-gap 4 mm. in width. The 

 guard-ring was soldered to the walls of the chamber which 

 was earthed ; it served to remove the ions produced by the 

 soft rays excited in the walls when struck by the y rays. 



Fijr. 2. 



M-— ih 



To £i£cr/foscore 



The face AB had a small opening 2x2 cm., covered with 

 thin mica and aluminium foil, through which the rays passed, 

 the brass walls being sufficiently thick to stop them. The 

 wall CD consisted of a glass plate fastened with sealing-wax 

 and also covered with thin aluminium foil to make it 

 conducting. The dimensions, as well as the distance between 

 the source R and the chamber, were so chosen that the beam 

 of 7 rays could not strike the electrodes and walls with the 

 exception of the thin aluminium of the front and back walls; 

 Consequently, only the ionization produced in the gas itself in 

 the region between the electrodes was measured. 



Let Ai be the ionization produced at the face AB in a thin 

 layer of air of unit thickness by rays of a given intensity. 

 At a distance x from AB the ionization will be K^e'^*, so that 



