464 M. 1. Pupin — Electrical discharges through poor 



denser effect of tinfoil coatings or other conductors placed on 

 the outside of a vacuum jar. 



The following experiment which 1 performed over a year 

 ago will explain my meaning more fully. The poles f g (tig. 

 7,) of a small Ritchie induction coil were connected to two glass 



The primary was fed by a \ h. p- 



beakers a b containing water 



alternator A, giving an alternating current of about 80 periods- 

 A resistance box E., regulates the strength of the primary cur- 

 rent. The speed of the motor which drives the alternator 

 regulated the periodicity of the current. 



A vacuum jar c d, consisting of two glass bulbs (each about 

 8 cm in diameter) connected by a tube of narrow bore, was im- 

 mersed into the beakers, one bulb in one beaker the other into 

 the other. The jar contained rarefied air at about 5 mm pressure. 



As soon as the bulb reached a certain depth a discharge took 

 place producing a perfectly steady and continuously diffused 

 crimson luminosity. The intensity of the luminosity increased 

 with the increase of the surface of contact between the water 

 and the bulbs. The same effect was produced by substituting 



