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BELL SYSTEM TECHNICAL JOURNAL 



delicate arrangement is that of Ramsauer (Fig. 5) ; the electrons enter 

 at B\, and are steered by a magnetic field along a semicircular path 

 through the slits B 2 — B*; electrons deviated even through a very 

 slight angle go against the partitions and are not received by the 

 electrometers connected at Ei or E 2 . Measurements with the two 



18 



15 



hz 



§ 9 

 I 



5< 



10 15 20 25 ^0 35 



Beschleuniqeno'e Spannung in Volt 



Fig. 7 



w 



*5 



electrometers, at two pressures of the gas, yield the data required. 

 The values of f- thus determined for argon, neon and helium are 

 plotted against the speed of the electrons in Fig. 6. The ordinates 

 of the short straight horizontal lines on the right represent the 

 squares of the radii relatively to other atoms. 



The effect shows itself, however, very distinctly in a much simpler 

 and more common device, a cylindrical three-element tube of audion 

 type with the grid very much closer to the filament than is the plate; 

 the plate is maintained at a potential a fraction of a volt higher than 

 that of the grid. Figs. 7 and 8, from a recent article by Minkowski 

 and Sponer, exhibit curves of plate-current versus grid-voltage in 

 helium, which does not show the effect in question, and argon, which 

 does. 3 In helium the current rises steadily as the increasing voltage 



3 The displacement of the curves by about -2 volts along the axis of voltages is 

 probably due in part to drop of potential along the filament, in part to neglected 

 contact-potential-differences. 



