Effed of Temperature on Spontaneous Ionization. 615 



much shorter than that required for the temperature of the 

 vessel to reach a steady state. The normal value of the leak 

 is maintained as long as the heating is continued. When 

 the source of heat is removed a temporary decrease of the 



Fia - . 1. Scale 



45 



TO ELECT/tOSCOPE 

 TO EARTH 



WATER INLLT 



~~®t 



AIR INLET -» 



>VAT£R OUTLET 



AfUBBEAf SI Or PEA 



SLATE SLATE 



A 



K 



■Ai/ff OUTLET 



leak ensues lasting for a period of the same order as that of 

 the increase, but, I think, a little longer. The variations 

 of the magnitude of the changes in different experiments 

 makes the estimation of this period very difficult, but it may 

 be roughly indicated as 15 seconds for the increase and 

 30 seconds for the decrease. After the initial decrease the 

 leak returns to its normal value and remains constant, 

 though the temperature of the vessel may continue to fall 

 perceptibly for half an hour. 



(The statement that the leak through the vessel when hot 

 is equal to that through the vessel when cold is not strictly 



