produced by the Corpuscles given out by Radium. 559 

 Figs. 3, 4, and 5 show that the relation between current 

 and pressure is of the form 



y 1 =—c-{-mp 

 when the lower plate is charged positively, and 

 7 2 = — c — mp 



when charged negatively, y x and y 2 denoting the currents, p 

 the pressure, and m and c positive constants. 



Fig. 5. 



P/7ES5URE 



The interpretation of this result is very simple : we have 

 negatively charged corpuscles constituting the deflectable 

 Becquerel rays travelling from PP to pp at a rate independent 

 of the pressure, on their way they produce equal numbers 

 of positive and negative ions in the gas, the rate of production 

 being proportional to the pressure. 



Let N be the number of corpuscles passing per second 

 through L and e the charge carried by a single corpuscle, 

 then the current due to the corpuscles alone is — N <>. 



Suppose that each corpuscle makes a collisions in traversing 

 one cm. of the gas at a pressure of one mm., let p be the 

 pressure, d the average distance travelled by the corpuscles in 

 going from PP to pp, and e' the charge carried by the ions 



generated in the gas. 



2 P 2 



