[brooks] damping of ELECTRICAL OSCILLATIONS 15 



Balls made of iron and of aluminium, replacing the brass balls at 

 the terminals of the spark-gap made no difference in the damping or 

 in the amount of demagnetization of the needle. From this it may be 

 concluded, that in the case of the oscillatory discharge it is the state 

 of the gas between the electrodes that affects the discharge, rather than 

 anything in the nature of the electrodes themselves, as in case of a con- 

 tinuous discharge. 



Small Pliicker tubes were placed in the circuit and the discharge 

 passed through them. They were found to offer resistajices varying 

 from fourteen to thirty ohms according to the nature of the gas or the 

 pressure to which the tube was exhausted. The resis,tance of some of 

 the tubes was so high that the oscillations were cut down entirely and 

 the discharge became unidirectional. 



In order to investigate the relation between the pressure of the air 

 at the spark-gap and the damping, the spark-gap was inclosed in an 

 air-tight glass bulb and the bulb exhausted. The damping rapidly 

 decreased as the vacuum became higher. An air-break of 5 centimetres 

 at a pressure of 100 mm. of mercury gave the same damping as an air- 

 break of 7 mm. at atmospheric pressure. Further investigations on the 

 effects of high vacua and the presence of different gases on the discharge 

 are in progress. 



