88 Prof. A. Wehnelt on the Discharge of 



impoverishment as regards such ions again increases, and 

 hence the cathode drop will increase. 



Fig-. 4. 



so 



3^ 



Timp 

























































I 





















f 



















/ 





















/ 





















/ 





















1, 

















































































































































v 1000 IlOO 1200 1300 MtOO'C 



Temperature. 



Now the glowing oxides emit, as we have seen, numerous 

 corpuscles. If the number emitted exceeds the number 

 absorbed by the passage of the current, there will be no im- 

 poverishment, i. e., the cathode drop will be zero. As the 

 current through the tube is increased, it finally reaches a value 

 such that the number of ions absorbed per unit of time by 

 the current becomes exactly equal to the number furnished 

 by the glowing oxide during the same interval. Up to this 

 value of the current, no impoverishment as regards negative 

 ions takes place, so that the cathode drop is zero. If now the 

 current through the tube be further increased, more corpuscles 

 will be absorbed than are generated, and the cathode drop 

 will begin to rise. 



Hence the current which I have defined as the limiting 

 current is that for which the absorption of negative ions and 

 the impoverishment thereby brought about just ceases to be com- 

 pensated by the corpuscles emitted by the glowing oxides. 



