3S6 Prof, Owens on Thorium Radiation. 



Table XI b. 



Thorium Oxide. Thick layer. 



Absorption or' radiation in air. 



Distance apart of fixed plates 3 cm. Lower plate 95 volts + 



Distance from oxide to lowest position of movable plate 



—d = 2'25 mm. 



Pressure 1 atmosphere. 



Distance in mm. 



Time of 100 div. in sec. 



Current. 



d= 2-25 



29-8 



100 



d+ 5-0 



410 



72-9 



d+100 



596 



500 



d+lb-0 



85-8 



34-7 



d+200 



1200 



24-7 



Table XI c. 



Thorium Oxide. Thick layer. 



Absorption of radiations in air. 



Distance apart of fixed plates 3 cm. Lower plate 05 volts 4- 



Distance from oxide to lowest position of movable plate 



= d = 2'25 mm. 



Pressure 2 atmospheres. 



' Distance in mm. 



d= 2-25 

 d+ 2-5 

 d+ 5-0 

 d + 10-0 



Time of 50 dir. in sec. 



Current. 



24-4 

 33-0 



48-4 

 88-4 



100 

 74-0 

 50-0 



27-4 



It will also be seen, by an inspection of the curves, that 

 the conduction-current between the two fixed plates, or, in 

 other words, the absorption in the layer of air between the 

 lower plate and the active material, varies very nearly as the 

 pressure for a particular distance of the lower plate from the 

 active material. If a thin layer of the oxide had been used 

 the proportionality would have been closer. 



My thanks are due to Prof. Rutherford, whose interest 

 and assistance made possible the investigation. 



