[MCLENNAN-KEYS] MOBILITIES OF IONS IN AIR 131 



Table IT. 



Mobilities of ions at various pressures in air. 



At all the pressures used this law of proportionality between i 

 and V^ was tested by giving different values to V and in all cases it 

 was found to hold. One of the different sets of readings obtained at 

 a pressure of 145-35 atmospheres will serve to illustrate this point. 

 The voltages applied, together with their squares and the corres- 

 ponding currents per square cm. cross section, are given in Table I. 

 They are represented graphically in Fig. 2 and it is clear from the 

 diagram that the relation between i and V- is a linear one. 



III. Results. 



Diagrams similar to that in Fig. 2 were plotted from the readings 

 taken with different voltages at all the pressures selected. From them 

 values for i/V^ were calculated for each of the pressures and on 



