The London, Edinburgh and Dublin philosophical magazine and journal of science . nt yellow positivecolumn began to rise up from the anode, and the potential-gradient in this part of the discharge increased very was at first thought that the tube had begun to leak rapidlyuntil a direct measurement with the Mc Leod gauge disprovedthis. The cathode-fall had also only shown a very slightdiminution. And on increasing the current the potential-difference (D—A) fell off again instantly to its formerimmeasurably small value. While confirming the old well-known observation that atordinary te
The London, Edinburgh and Dublin philosophical magazine and journal of science . nt yellow positivecolumn began to rise up from the anode, and the potential-gradient in this part of the discharge increased very was at first thought that the tube had begun to leak rapidlyuntil a direct measurement with the Mc Leod gauge disprovedthis. The cathode-fall had also only shown a very slightdiminution. And on increasing the current the potential-difference (D—A) fell off again instantly to its formerimmeasurably small value. While confirming the old well-known observation that atordinary temperatures the cathode-fall increases writh increas-ing current-density, this table also shows that, on the other Discharge of Electricity through Gases. 703 hand, at high temperatures the cathode-£all diminishes withincreasing current. The measurements of the fall of potential along the dis-charge at different temperatures o£ the anode are collectedin Tables XV. and XVI. at pressures of 1*83 and 063 The effects o£ temperatures on the fall of Fig. 50Q_,r KJOO 5QC Temperature of Anode, ° C. potential close to the anode are shown in fig. 8. This*; anode-fall (K —D) shows a steady diminution with risingtemperature. The changes of potential-gradient near thecathode were probably mainly due to its slow warming up, theamount of which could not, however, be measured. It will be noticed that though the total potential-differenceacross the electrodes diminishes, yet the anode-fall(K — D) increases with increased current at all temperaturesof the anode, though, perhaps, less markedly at high tempera-tures. The potential-gradient in the positive column, as wehave noticed before, diminishes with increasing current. I am glad of this opportunity to express my indebtednessto Professor Thomson for many encouraging suggestionsduring the progress of the work. St. Johns College, Cambridge. [ 704 ] LXXV. Excited Radioactivity and Ionization of the Atmosphe
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