Discharge of Electricity through Gases. 703 



hand, at high temperatures the cathode-£all diminishes with 

 increasing current. 



The measurements of the fall of potential along the dis- 

 charge at different temperatures o£ the anode are collected 

 in Tables XV. and XVI. at pressures of 1*83 and 0'63 mm. 

 respectively. The effects o£ temperatures on the fall of 



Fig. 8. 

 300 f 



' 50Q_,r KJOO 5QC 2.C00 



Temperature of Anode, ° C. 



potential close to the anode are shown in fig. 8. This 

 * ; anode-fall" (K — D) shows a steady diminution with rising 

 temperature. The changes of potential-gradient near the 

 cathode were probably mainly due to its slow warming up, the 

 amount of which could not, however, be measured. 



It will be noticed that though the total potential-difference 

 across the electrodes diminishes, yet the "anode -fall" 

 (K — D) increases with increased current at all temperatures 

 of the anode, though, perhaps, less markedly at high tempera- 

 tures. The potential-gradient in the positive column, as we 

 have noticed before, diminishes with increasing current. 



I am glad of this opportunity to express my indebtedness 

 to Professor Thomson for many encouraging suggestions 

 during the progress of the work. 



St. John's College, Cambridge. 



