H. V. Gill — Electric Discharge in Gezsster Tul 



In studying the strata we must bear in mind that the tube 

 is itself a condenser, and must therefore influence the dis- 

 charge. These seem therefore good grounds for the theory 

 we have proposed. In the experiments we are about to 

 describe we think there will appear a striking confirmation, 

 and proof of the truth of this explanation. 



Experiments with vacuum tubes present peculiar difficulty 

 owing to the nature of the phenomenon. Besides, there is the 

 further disadvantage of the necessity of an expensive appara- 

 tus. For these reasons we sought for a long time some means 

 that would be at the same time simple and adequate. The 

 obvious way to test the truth of this theory seemed to be to 

 endeavor to repeat Kundt's experiment with a Geissler tube. 

 But against this was the fact that waves in so rarefied a 

 medium would seem to be incapable of producing so marked 

 a mechanical result. Here, again, however, is the fact that 

 the condensations produced by the electric spark are very 

 much more intense than those produced by ordinary sounding 

 instruments. However we eventually adopted this method, 

 and as will appear immediately, with excellent results. Since 

 we argued that the effect in a rarefied gas was the same as that 

 in air under normal conditions, it seemed logical to test the 

 theory from the very foundation. Hence we shall at first deal 

 with some interesting results obtained in air, and proceed grad- 

 ually to the stratified discharge. 



We have already seen that Mach proved electric sparks to 

 produce disturbances in the surrounding atmosphere exactly 

 similar to those produced by sounding bodies, and that Lodge 

 produced musical notes by the waves produced by the oscilla- 

 tions of such sparks. "One sees clearly why one gets a musi- 

 cal note: the noise of the spark is due to the sudden heating 

 of the air." (We might also add the sudden expansion caused 

 by a spark which is due to electrical causes.) " And now if the 

 heat is oscillatory the sound will be oscillatory too, but both 

 will be an octave above the electrical oscillation, if I may so 

 express it, because two heat pulses will accompany every com- 

 plete electric vibration, the heat production being independent 

 of the direction of the current." 



Evidently if we were to replace the vibrating glass r^\ in 

 Kundt's experiment by an electric spark, we ought to get 

 nodes and consequently heaps of powder in the Bame manner. 

 Since the frequency of oscillation of a spark is s<» exceedingly 

 high, these heaps would be very near together. 



This then was the first experiment. § 



A horizontal glass tube almost one meter long was spnnkled 

 throughout its length with lycopodium powder. The two ter- 

 minals of a small Voss machine were placed about 10 apart 



