produced from a Gas by High-Speed Cathode Rays. 207 



definite potentials. The reading for v = was taken both 

 before and after taking the reading for v= a desired value, 

 v' say, and the mean of these two readings for v = was 

 taken as representing the value for v = at the time of 

 taking the reading for v=v'. The reading for v = v' was 

 expressed in a percentage of the mean reading for v = 0. 



v. 







0-3 







0-7 







0-5 







Deflexion 

 in 20 sees. 



13-6 cms. 



132 



13-8 



11-1 



12-0 

 14-3 



Mean of 

 Deflexion 

 for v=0. 



- 137 



13-95 



Deflexion 



as percent. 



of this mean. 



1000 



96-3 



79-6 



J 



14-2 



84-5 



When the deflexion for v = changed too much, the ex- 

 haustion of the apparatus was renewed. The deflexions 

 were observed for time varying from 10 seconds to 60 seconds. 

 The final results selected for the percentages of the currents 

 were the averages of a considerable number of observations. 



§ -1. Experiments on the Positive Ions. 



Positive ions are produced in the gas at the same moment 

 as the negative corpuscles are ejected from the gas atoms 

 under the bombardment of the primary rays. The initial 

 velocity of the positive ions therefore must be due to the 

 recoil caused by the corpuscles. Hence we have 



MV = mv, 



where M and w";are the masses, and V and v the velocities 

 of the positive ion and the corpuscle respectively. Since 

 their kinetic energies are 



p/LV 2 = E<>, and ±mv 2 = We, 



where E and E' are the potential falls corresponding to the 

 velocities V and v respectively, we have 



Taking the initial velocity of the corpuscle, in accordance 

 with Sir J. J. Thomson's result, as that corresponding to a 

 potential fall of 40 volts, then in the case of a hydrogen 

 atom, m/M = 1800, and we have E = 0*02 volt approximately. 



