Prof. Owens on Thorium Radiation. 387 



Table XI d. 



Thorium Oxide. Thick layer. 



Absorption of 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 3 atmospheres. 



Distance in mm. 



Time of 100 div. in sec. 



Current. 



d=2-25 

 d+2-50 

 d+ 5 

 d+75 



410 



660 



1034 



1510 



1000 

 620 

 400 

 270 



Fig. 13. — Absorption Curve. Air. 



Thorium Oxide. Thick layer. Fixed plates .°. mm. apart. I. | atmosphere pressure ; 

 II. 1 atmosphere pressure ; ILL 2 atmospheres pressure ; IV. 3 atmospheres pressure. 



O 



10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 



Distance in milliin. 



2 E 2 



