Cathode Fall from Hot Carh 



199 



curves -how a much more gradual maximum intensity towards 

 the middle of the bright band succeeded by a slightly lower 

 minimum in the dark space. This difference is probably due 

 to the composite nature of the strise in air and other mixed 

 gases, and is accompanied by a difference in the appearance 

 of the striae. In those here alluded to. the striae presented a 

 sharp odpre of maximum brightness towards the cathode, just 

 in front of which bright part the sudden rise of potential 

 occurred. The brightness then shaded off gradually towards 

 the anode, and only became quite dark at a short distance in 

 front of the next stria. 



From the indications of my previous work, T was encouraged 

 to pay special attention to the influence of increased current 

 on the distribution of potential along the discharge. The 

 first method of observation was to place the intermediate 

 electrodes at any particular point, and then, keeping the 

 temperature of the cathode accurately constant, to vary the 

 current through as wide a range as it was possible to obtain 

 a steady discharge with, and simultaneously to record the 

 differences of potential. By doing this for a series of points 



Fig. 2. 

 Temperature = 1140°. Pressure = 0"55 mm. 



600 



^500 



x 



400 















^ 



-3'=5iB 











^ 









/ 











15 20 



Ct/ZF/i 



25 



along the discharge and plotting the results as in fig. 2, it 

 w;.s thence possible to plot the distribution of potential along 

 the discharge for a series of different values of the current, 



