810 . Dr. Norman Campbell on 



Fig. 3 gives the results o£ the measurements when Y 1 is 

 constant and V 2 variable, the value of the current when 

 V 2 = being in all cases put equal to 1. Any ordinate of a 

 curve gives the fraction of the rays emerging from the box 



Fig. 3. 



/.o 



3 A 



Xo 



1 8 f lo il ix /3 //, is ti q is /f 



with a velocity not less than that given by the corresponding 

 abscissa. It will be seen that so long as the value of Y 1 (i. e. 

 the velocity with which the electrons liberated from Z strike 

 A) is not greater than 10 volts, the curves are nearly straight 

 lines and the velocities of the rays emerging from A are very 

 nearly equally distributed over the range to V,. On the 

 other hand, when Yi is not less than 12, the curves have a 

 completely different form ; the greater proportion of the rays 

 emerging from A have low speeds ; the proportion of rays 

 having a speed less than 2 volts increases with Y 1 until it 

 reaches a definite limit (0*35), when V x = 20. When Y 1 is 

 greater than 30 the distribution of the velocities of the rays 

 emerging from A appears to be independent of V l5 the 

 maximum speed of the rays being about 30 volts. Experi- 

 ments were made with values of Y 1 greater than 40, but they 

 were not very accurate ; but no indication of a change in the 



