.1/?' at diferent Temperatures (Did Pressures. 237 



"), where the abscissse represent the pressure in nnn. of 

 :curv and the ordinates the current in E.S. units. 



Ionization in Air and Hydrooen at different pressures. 



Air. 



1 



Hyd 



■ogen. 





Current between 



, 



Current between 



Pressure in 



Electrode and 



Pressure in | 



Cylinder and 



mm. of Hg. 



Cylinder in 



mm. of Hg. ! 



Electrode in 





E.S. units. 





E.S. units. 



76.-) • 



305x10"'* 



790 



2-88x10""* 



435 



3-22 „ 



422 



2-33 „ 



299 



2-99 „ 



242 



1-84 „ 



291 



2-85 „ 



116 



1-13 „ 



179 



2-66 „ 



i 





136 



2-54 „ 



1 





105 



2-17 „ 



1 





80 



1-95 „ 



1 





59 



1-42 „ 



1 

 1 





27 



0-69 „ 



1 





It would seem as if the air in the vessel Avas hardly satu- 

 rated even when the cylinder was charged to a potential of 



80 ctnofHg 



1000 volts, but from the shape of the curve it will be seen 

 that the current varies very slowly with the pressure down to 

 a pressure of 130 mm. of mercury; and below 80 mm. the 

 current is proportional to the pressure, while above 300 mm. 

 the current is almost independent of the pressure. In 

 hydrogen the current varies rapidly with the pressure but not 

 proportionally. This is partly due to the hydrogen not being- 

 pure, and as the vessel was not quite air-tight there would 

 be a greater proportion of air at the lower pressures than at 

 the higher. 



These results would show that the walls of the vessel were 

 slightly radioactive as Wilson suggested, and that in the 

 cylinder used the radiation was all absorbed before it pene- 

 trated the air in the vessel. In the case of hydrogen the 

 radiation was not all absorbed b}' the gas at the ]jressures 



