Mr Campbell, Discontinuities in Light Emission. 321 



Eart/} 



Fig. 3. 



^1, /^g photo-electric cells. 



Bj small accumulators. 



B^, Bo accumulators for potentiometer circuits Pj, Po 



G sub-divided capacity box (1 micro-farad). 



E electrometer. 



E' tilted electroscope. 



R Xylol-alcohol resistance. 



G, G' guard-rings. 



K key insulating electrode system. 



