512 



Transactions. — Miscellaneous. 



A Voss machine was used to charge up the jars. It will 

 be seen that the resistance of the spark-gap diminishes rapidly 

 as the capacity of the condenser is increased — i.e., as the 

 quantity of electricity that passes through the spark-gap is 

 increased. 



The effect of keeping the capacity and inductance constant 

 and varying the spark-length was then proceeded with. 



These observations show that the spark-gap increases 

 in resistance rapidly as the length of spark is increased. 

 Short spark-gaps have low resistances, and long spark-gaps 

 high resistances. 



In all these experiments a Voss machine was used to charge 

 up the jars. If the Voss is replaced by a Eumkhorff coil, under 

 certain conditions it is probable that the resistance is much 

 lower. If a Hertz dumb-bell vibrator is excited by a Voss no 

 action in a resonator can be detected. When a Eumkhorff 

 coil is used oscillations are set up in neighbouring circuits, but 

 only when a certain kind of spark is given by the coil. This 

 spark was called by Hertz the "active" spark, and it is 

 probable that the resistance of the spark-gap is much less with 

 the active spark than with the ordinary discharge. Usually 

 with a spark-gap of about fcm. the vibrations are damped 

 down very rapidly, and the second half-oscillation has not half 

 the amplitude of the first. 



