72 Mr Zeleny, On the Conditions 
repeated after the potential has been increased above its former 
value. On continuing the procedure, the liquid surface soon takes. 
on a continuous up and down motion, a current of like period passing 
to the plate. At last the oscillations become too rapid to follow 
and the top of the meniscus simply appears blurred. On increasing 
the voltage further, the outline of the meniscus suddenly becomes! 
perfectly distinct and the current becomes steady, a telephone 
receiver in the circuit now giving no sound. At this stage of thel 
discharge the luminosity is confined to a very thin coating on thei 
liquid surface, whereas in the intermittent stage a faint light wasi 
observed extending, in the form of a brush, a good portion of the) 
distance to the plate. | 
ZD 
WS 
WOON 
TO EARTH 
Fig. 1. 
3. Experiments with water surfaces in air at reduced pressures 
show that the intermittent stage of the current is not obtained at_ 
pressures below about 60 cms. of mercury. In this region the 
current begins with a jump to a value of some magnitude, the 
meniscus of the liquid snapping back simultaneously to a lower 
