. The Bell System technical journal . e top of the aforesaid interval). 1* Rohde devotes so much of his attention to the maintaining-potentials (seebelow) that his allusions to the onset-potential are scanty, and their degree of gener-ality is hard to assess. 104 BELL SYSTEM TECHNICAL JOURNAL In a narrow tube, a greater voltage is required for breakdown than ina broad one—at pressure 1 mm., twice as great a voltage for a as for one of diameter. This last is an illustration ofthe effect of the walls; probably they influence the preliminaries tobreakdown by capturing and reta
. The Bell System technical journal . e top of the aforesaid interval). 1* Rohde devotes so much of his attention to the maintaining-potentials (seebelow) that his allusions to the onset-potential are scanty, and their degree of gener-ality is hard to assess. 104 BELL SYSTEM TECHNICAL JOURNAL In a narrow tube, a greater voltage is required for breakdown than ina broad one—at pressure 1 mm., twice as great a voltage for a as for one of diameter. This last is an illustration ofthe effect of the walls; probably they influence the preliminaries tobreakdown by capturing and retaining the electrons which approachthem from the gas, so that the ionizing agencies at work in the gas mustbe strengthened to compensate that loss. Townsend and Nethercotalso record a Vs-vs-p curve with a minimum, for frequency lO. If one knew only of the foregoing papers, one would resume thesituation as follows: for any value of pressure, breakdown-potentialdiminishes steadily with increase of frequency, but the diminution is. pressure: in mm Hg Fig. 17—Onset-potential vs. pressure, in rarefied hydrogen, for self-sustaining glowat the indicated wave-lengths. (H. Gutton, Annates de Physique.) very small all the way from i = 0 to v = 10*^; for any value of fre-quency, the curve of Fs-vs-/? has a single minimum; the coordinatespsm and Vsm of that minimum decrease with increasing v. Therewould be wide gaps in the range of frequency over which these state-ments had been tested, but nothing would suggest that there might bediscrepancies within the gaps. However, the situation is not sosimple. Mention must be made of remarkable and perplexing dataobtained by C. and H. Gutton and collaborators of theirs, mainly withexternal-electrode tubes. Fig. 17, relating to hydrogen, is taken from some of H. Guttons CONTEMPORARY ADVANCES IN PHYSICS 105 most recent work: it is a set of Fs-vs-p curves for various frequenciesof an extremely wide range (the wave-lengths in meters are
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