Cathode Fall from Hot Carbon. 205 



begins at a lower P.D. with increasing temperature of the 

 cathode, might seem to indicate its being somehow directly 

 clue to the negative corpuscles which we know are given off' 

 in large numbers by the hot carbon. The effect of these, 

 however, is to lessen the steepness of the gradient at the 

 surface itself, and to diffuse the field, as it were, over a 

 further distance, and so increase the region through which 

 the positive ions may produce new ions by collision, while at 

 the same time lessening the consumption of positive ions at 

 the surface of the cathode. 



These considerations give a special theoretical interest to that 

 part of the curve where the current begins to increase again 

 more rapidlythan the cathode-fall rises. Anumber of measure- 

 ments at this portion of the curve are shown in fig. 6 (p. 206), 



and distance 



with rlie temperature ( R= j< 



in cms. from the cathode 

 Tables II. and III., I have 

 of the curves which were 

 figure. 



Table II. 



R 



" 



=•664, p=0-3 



2 mm. 



Observed 



Current. 



Cathode-Fall. 



Deflexion. 



Deflexion, 

 28-75=10-^ amp. 



Volts. 



48-5 



1649 



950 



414 



140-8 



910 



325 



1102 



855 



28-3 



96-1 



836 



194 



1360 



770 



121 



41-1 



704 



2O0 



680 



785 



1-2 



61-9 



767 



i 1 o 



391 



698 



37o 



37'5 



710 



336 



:;:;•< ; 



694 



30-0 



300 



681 



24 7 



247 



664 



204 



20-4 



651 



156 



15(5 



631 



155 



15-5 



630 



12 3 



Vi:\ 



622 





9-8 



CIS 



70 



70 



591 





5-2 



576 



24-fi 



4-68 



.~>73 



17-7 



3-56 



556 



10-7 



■in:) 



530 



pressure (p), 



(d) marked on each curve. In 

 repeated the results for a couple 

 taken beyond the limits of this 



Table III. 

 ~ =-591, y> = 0-43 mm. 



Observed 



Current. 



Cathode-Fall. 



Deflexion. 



Deflexion, 

 28 - 75 = 10— 3 amp. 



Volts. 



16-8 



16-8 



570 



11-8 



11-8 



543 



8-8 



8-8 



520 



70 



70 



501 



10-3 



103 



535 



293 



293 



607 



23-3 



23-3 



599 



355 



35-5 



630 



44-5 



44-5 



(»77 



51-5 



51-5 



(591 



15-3 



520 



690 



21 -5 



74-5 



741 



28-1 



95-4 



785 



18-6 



r»3-2 



735 



30-4 



L033 



824 



34 



1 15-5 



852 



