Two Tons produced in Gases by Wont gen Radiation. 141 



Leaving the voltages on the plates as before, but increasing 

 the distance between them to 16 centim., which necessarily 

 sacrifices the uniformity of the field and decreases the potential 

 gradient, deflexions were obtained which are shown graphically 

 in fig. i ( . 



It is seen from both curves that near each plate there is an 

 electrification of the opposite sign to that of the plate, and 

 that the quantity of the electrification falls off rapidly with 

 the distance from the plates. 



The two oppositely charged layers at the plates exert a 

 powerful polarization effect, and are able to reduce by a large 

 part of itself the electric force in the middle between the 

 plates, as will be shown in considering the potential gradient 

 between two plates during conduction (§ 11). 



The formation of these free charges at the plates is readily 

 understood from a general consideration. 



The two kinds of ions, as soon as they are formed by the 

 rays, are given a resultant motion in opposite directions 

 through the air by the action of the electric force, and this 

 motion continues until they reach one of the plates or suffer 

 recombination. If we consider a narrow layer of air at one 

 of the plates, some ions of the kind that is moving towards 

 that plate are entering this layer at one side, and some are 

 leaving it at the other or plate side. Ions of the opposite 

 sign, however, are only leaving this layer, as none can enter 

 from the side bounded by the plate. There are thus two 

 systems of ions, one of which is moving towards a boundary, 

 and the other of which is moving away from the same 

 boundary. 



This motion produces an excess at each plate of the kind 

 of ions that are moving towards that plate. 



The charge is not primarily due to any accumulation of 

 the ions, but simply to a separation of the two kinds that are 

 produced. At other points between the plates the ions may 

 be equally numerous, but if the two kinds are equally abundant 

 they produce no resultant effect. 



The formations of the two charges are limited in amount 

 by the action of the new electric and diffusion forces produced 

 by them. 



The difference of potential between the plates has a large 

 effect upon the production of the charges. 



If the ions are moving very slowly the charges exist almost 

 entirely at the plates; but as the potential gradient increases 

 the charge in the layer increases in amount and the charged 

 area itself increases in extent. 



