re 



ProceedvHjis of the Royal Irish Acudciiii/ . 



Hence 



and 



ka VI = Q 



aVl 



(3) 



The equation (2) also shows that for a voltage V less than V the ions of 

 mobility h will be taken out of a \'olume Q' of air given by 



Q' = kaV'l 



Hence, if these ions are unifonnly distributed through the air, the current 

 obtained by their agency is proportional to the voltage ; and the graphical 

 representation of this relation is a straight line through the organ until the 

 saturation point is reached. If there are a finite number ?! of distinct types 

 of ion, each with definite mobility and uniformly distributed in the air, the 

 relation between ciuTcnt and voltage will be repi-esented by a curve, any 

 ordinate of which is the siun of the ordinates (for the same voltage) of n curves, 

 each of these curves consisting of a straight line thi-ough the origin till the 

 saturation voltage is reached, after which the line is parallel to the voltage 

 axis. The curve, therefore, which would represent the relation between 

 current and voltage would be a crooked curve concave to the voltage axis, 

 consisting of n parts, each of which is a straight line, and finally becoming 

 parallel to the voltage axis. If the ions were not di\nded into distinct groups, 

 AverageValocvby of Air Blast =210 Cms per Se^ 



5 



'' I i - I I I 



I I i I I I 



Volts 



Fl<;. 4, 



but had mobilities merging gradually from one into the other, the graphical 

 representation would be a continuous smooth curve concave to the voltage 

 axis, and finally turning into a straight Line parallel to this axis. 



In seeking the actual relation between current and voltage, it is not 

 convenient to constract the whole of the cui've from saturation downwards in 

 one series of observations, because if an air-blast is used of such velocity that 



