130 Prof. J. Zeleny on the Ratio of the Velocities of the 

 These results are represented by curve II. in fig. 5. 



Fig. 5. 



80 



60 



40 



20 





/ 



CO, 



I 



s? / 



4 



R ! 



/Ai 



/* 



K A 



^ / 





A 



? 









X = + 



8 



16 



24 



5? 



^7//^ 



It appears that in carbonic acid gas the two ions travel 

 with almost, if not exactly, the same velocity. 



Curve I. shows how the deflexions increased with the 

 voltages used when there was no blast and the gas was at rest, 

 and comparing with curve II. the retardation of the ions, due 

 to the blast, is made apparent. Curve II. is in fact a displaced 

 curve I., the displacement being caused by a decrease in the 

 velocity of the ions produced by and equal to the velocity of 

 the gas-stream. The electric force necessary to give to the 

 ions a velocity equal to the average velocity of the blast is then 

 obtained from the voltage represented by this displacement 

 and from the distance between the plates. Thus, by measuring 

 this potential gradient and the velocity of the blast, the velocity 

 of the ions can be determined. The writer has not, in this 

 investigation, attempted to develop this method, but it may 

 be freer from objections and more accurate in practice than 

 methods heretofore used. A single determination made with 

 air gave roughly for the velocities of the positive and negative 

 ions respectively, 2*1 centim., and 2'6 centim. per second for 

 a potential gradient of one volt per centimetre, 



