128 Prof, J. Zeleny on the Ratio of the Velocities of the 



Table I. — Air. 



Potential of Q 

 in volts. 



Electrometer 

 deflexion. 



Potential of Q 

 in volts. 



Electrometer 

 deflexion. 



+ 10 



00 







+20 



+ 15 







+30 



+ 3 



-30 



- 5 



+40 



+ 4-5 



-40 



- 8 



+ 50 



+ 7 



-50 



-13 



+54 



+ 8 



-54 



-18 



+58 



+ 11 



-58 



-26 



+64 



+ 14-5 



-64 



-43 



+68 



+21 



-68 



—55 



+ 72 



+ 28-5 



-72 



-68 



+76 



+ 36 



-76 



-80-5 



+80 



+48 







+88 



+71 







These results are shown graphically in fig. 4, where the 

 abscissas represent the voltages used and ordinates the corre- 

 sponding deflexions obtained. 



At B the potential gradient has increased to such a value 

 that the ions are beginning to make their way against the 

 main blast of air. That some reach the gauze for points 

 between A and B is due to irregularities in the stream of air. 

 It is possible also that there are some few ions in a gas that 

 travel faster than the majority of the ions. 



Curve I. represents the case when the negative ions, and 

 curve II. the case when the positive ions are moving against 

 the stream respectively. 



It is seen that the velocity of the positive ions for the same 

 potential gradient is less than that of the negative ones, since 

 to drive the same quantity to the gauze against the air-current 

 a greater potential gradient is required for the positive than 

 for the negative ions. 



In air the difference of velocity of the ions is quite large, 

 but in some gases it is small or nothing at all, 



