CHAPTEE IV. 

 FORESHADOWING OF THE ELECTRON. 



Separate Existence of the Electric Unit suggested 

 by Conduction in Gases. 



WE will now leave liquids and proceed to conduction 

 by ratified gases, that is to say to the phenomena 

 seen in vacuum tubes. If a long glass tube, say a 

 yard long and two inches wide, with an electrode at 

 each end, and full of common air, is connected to an 

 induction coil and attached to an air-pump, the 

 ordinary spark-gap of the coil being, say, two or 

 three inches wide, we find that for some time after 

 working the pump the electric discharge prefers the 

 inch or two of ordinary air to a long journey through 

 the partially rarified air in the tube ; but that at a 

 certain stage of exhaustion, one which any rough 

 air-pump ought to reach, this preference ceases. A 

 flickering light appears in the tube, readily visible in 

 the dark, which very soon takes on the appearance of 

 red streamers like the Aurora Borealis ; and soon the 

 sparks outside in the common air cease, showing that 

 the rarified air is now the better conductor and the 

 preferable alternative path. Let the exhaustion 

 proceed further the axis of the tube becomes 

 illumined with a glow, which is now much brighter, 



