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BELL SYSTEM TECHNICAL JOURNAL 



In a narrow tube, a greater voltage is required for breakdown than in 

 a broad one — at pressure 1 mm., twice as great a voltage for a 1.5-cm. 

 tube as for one of 3.9-cm. diameter. This last is an illustration of 

 the effect of the walls; probably they influence the preliminaries to 

 breakdown by capturing and retaining the electrons which approach 

 them from the gas, so that the ionizing agencies at work in the gas must 

 be strengthened to compensate that loss. Townsend and Nethercot 

 also record a Vs-vs-p curve with a minimum, for frequency 7.5- lO''. 



If one knew only of the foregoing papers, one would resume the 

 situation as follows: for any value of pressure, breakdown-potential 

 diminishes steadily with increase of frequency, but the diminution is 



0.3 0.4 



pressure: in mm Hg 



Fig. 17 — Onset-potential vs. pressure, in rarefied hydrogen, for self-sustaining glow 

 at the indicated wave-lengths. (H. Gutton, Annates de Physique.) 



very small all the way from i' = to v = 10*^; for any value of fre- 

 quency, the curve of Fs-vs-/? has a single minimum; the coordinates 

 psm and Vsm of that minimum decrease with increasing v. There 

 would be wide gaps in the range of frequency over which these state- 

 ments had been tested, but nothing would suggest that there might be 

 discrepancies within the gaps. However, the situation is not so 

 simple. Mention must be made of remarkable and perplexing data 

 obtained by C. and H. Gutton and collaborators of theirs, mainly with 

 external-electrode tubes. 



Fig. 17, relating to hydrogen, is taken from some of H. Gutton's 



