344 



Mr. W. B. Haines 



There was no consistent evidence of more than one kind of: 

 positive ion. The values indicate a departure from the law- 

 Pi^ const., especially at lower pressures, when the mobility 

 is smaller than would be predicted. 



Both the negative ions A and B follow this law very 

 closely, the constant in the one case being just half that in 

 the other. At pressures higher than half an atmosphere some 

 readings give a mobility higher than is indicated by the 

 formula, the dotted curves showing approximately the limits 



Ei£. 4. 



VO 80 



Pressure 



within which the values lie. This would be the case if the 

 limit were exceeded at which the proportionality of velocity 

 to field breaks down, i. e. the velocity impressed on the ion 

 being sufficient to cause it to break up and become lighter. 



