496 Transactions. — Miscellaneous. 



For frequencies of 100,000,000 and upwards, however, 

 where the quantities of electricity set in motion are in general 

 small, it gave very satisfactory results. 



Plate XLIX., Fig. 11. 



B and C were two plates of metal about 20cm. square, 

 arranged as in Hertz's experiment. A small solenoid of two 

 turns (which did not use more than 2cm. of wire) was placed 

 in series with discharge circuit at D. When an induction 

 coil causes a discharge at A, oscillations are set up, which 

 have a frequency in this case of over 100,000,000 per second. 



When two turns were wound round the detector, the de- 

 flection fell from 300 to 250 in one direction and 300 to 274 in 

 the other, showing that the decay of amplitude of the oscilla- 

 tions is about equal to that of the ordinary leyden-jar dis- 

 charge. 



It is unfortunate that I did not particularly distinguish 

 between the "active' 1 spark and the "ordinary" spark. 

 Hertz had observed that the active spark was the only 

 one that set up oscillations in neighbouring conductors; and 

 from the very rapid decay of amplitude in this case it is 

 almost certain that it was not the "active" spark that 

 occurred. 



This is confirmed by the fact that the effects on the needle 

 differed very little whether the spark was obtained by the use 

 of the Yoss machine or from a Eumkhorff coil, while Hertz 

 expressly states that oscillations in a neighbouring conductor 

 are not excited unless a large Eumkhorff coil is used, and can- 

 not be excited at all by the use of a Voss machine. 



The effect of currents in a resonating circuit was next in- 

 vestigated. 



Plate XLIX., Fig. 12. 



This experiment was arranged after the same method as 

 Hertz's experiments. C and C were two conductors of small 

 capacity attached to ends of circuit in order to give discharging 

 circuit a sensible capacity ; ab c d was the resonating circuit, 

 m spark-gap in resonator. 



When discharge passed across B oscillations were set up 

 in the resonating circuit. The detector was placed in the 

 side c a of the resonator, and when there were three turns of 

 wire round detector deflection fell from 300 to 253. 



It was not at all necessary that a spark should occur at m 

 to get an effect on needle, the effect being still considerable 

 when the knobs at m were 1ft. or more apart. 



If one side of the rectangle was removed an effect was 

 still observed, but not of such magnitude as when the circuit 

 was in unison with the primary. 



