ELECTRIC TRANSMISSION -IN 



149 



ix</A 

 spark into the circuit. The electricity then accumulate 



and a rapid succession of brilliant discharges is the resul 



The same effect can be produced by opening the 

 switch, connecting the tube with its terminals, arid 

 slightly separating the sliding electrodes P and R. 



When the spark between P and R is apparently 

 continuous, the pulsations in the induced discharge 

 through the tube are distinctly visible in the alterna- 

 tions of light and shade; proving that the discharge 

 consists of a series of distinct impulses. 



Fig. 45 Rotary Movement in High Vacua. 



ELECTRIC TRANSMISSION IN HIGH VACUA. The re- 

 sidual air in the ordinary Geissler tube is about jo^An 

 of an atmosphere, but Crookes has produced tubes in 

 which the residual is less than Tutr&injtf f an atmos- 

 phere ; and the electric discharge in such tubes presents 

 certain peculiarities not observed in ordinary vacua. 



Electric action on substances inclosed in such tubes, 

 and on the glass itself, is increased in the ratio of the in- 

 creased vacuum; since those substances receive the force 

 of energy which, in lower vacua, is expended on the air. 



This increased action is shown by an increase in the 

 light and heat developed in them, and in the attractive 



