Nipher — Nature of the Electric Discharge. 7 



It is such a system of air waves that has been described 

 as a ^* series of partial discharges'' when the discharge 

 of a Leyden jar is examined by means of a rotating 

 mirror. 



THE DEAINAGE COLUMN. 



Since the publication of former papers the writer has 

 listened to criticism for the use of the phrase ^^ drainage 

 column.'' It has been urged that this simply means a 

 column of ionized gas. It seems necessary to say that 

 the use of this phrase is of advantage in explaining phe- 

 nomena of electric discharge on the one-fluid hypothesis. 

 A mass of air is said to be ionized by X-rays. In such 

 a mass of air, some of the air molecules have lost a por- 

 tion of their normal charge of negative corpuscles, which 

 have been loaded upon others. These two classes of mole- 

 cules are mingled together. The average charge per 

 molecule has not been changed. The normal condition 

 soon returns, if the mass of air is left to itself. This is 

 not the condition when a mass of air is under the in- 

 fluence of either terminal of an influence machine. To 

 say that such a mass of air is ionized, is to tell less than 

 the whole story. The corpuscles are drained out of the 

 air in the vicinity of the positive terminal. They are 

 forced out of the negative terminal and into the air in 

 front of it. Of course it is not claimed by anyone that 

 the so-called positive ions issue from within the positive 

 terminal or pass into the negative terminal. The col- 

 umn of air between the terminals is a conductor, but it 

 is a gas, and its molecules are free to move. A transfer 

 of the fluid from molecule to molecule takes place, as it 

 does in a copper wire. The corpuscles leave a molecule 

 which attracts them, and they go to another which attracts 

 them. They are forced out of the negative terminal 

 against its attraction for them and they are drawn into 

 the positive. Cakes of ice would yield under the feet 

 of a runner who should leap from one to another, as air 

 molecules do in an electric discharge, although the ma- 



