Mr Vegard, An experiment on ionisation with <y rays. 81 



Mean value 8 = + 0,0002. 



Part II. Angle 90°. 



Interval 



40 divisions 

 30 „ 

 30 „ 





0,3925 

 0,5366 

 0,5354 



1 



tab' 



0,3922 

 0,5379 

 0,5397 



+ 0,001 

 -0,002 

 -0,008 



Mean value 8 = - 0,003. 

 The time is given in minutes. 



The table shows that within the limits of experimental error 

 the ionisation of air with y rays is strictly an additive property, 

 and that, as far as the effect sought for is concerned, the experi- 

 ment has given a negative result. In view of the previous 

 considerations the result only shows that at least one of the two 

 conditions necessary for the effect must be wanting; but apart 

 from its connection with the previous considerations the result is 

 of interest in itself, as giving a property characteristic of ionisation 

 with 7 rays. 



