﻿Potential and the Velocities of Electrons. 583 



work a zero method was employed. The lead box and the 

 perforated box C were insulated from D and from the 

 earth, and their potential so regulated by the sliding con- 

 tact S that there was no deflexion of the electrometer 

 connected with D. Then the voltmeter V gave a direct 

 reading of the contact difference of potential between 

 C and D. 



4. Effect of the Field between the Brass Box B and the 

 Perforated Box C. — Before taking up the effect of the 

 contact difference of potential, the effect of the field which 

 sweeps the electrons from the perforated box C to the 

 box B will be shown. In Table I. are given the readings 

 for curve (a) (PI. IX. fig. 4). In this case the difference 

 of potential between C and B was 400 volts ; and C was the 

 platinum-foil box, electrolytically copper-plated. These 

 readings are a type of those obtained for all the curves in 

 this paper, except that in the following sections at least ten 

 ratios were averaged to get each point on the curve. 



Table I. 



V. 



A. 



E. 



V. 



A. 



50 

 94 

 52 



105 

 50 



104 

 55 

 98 

 50 

 95 



E. 

 •53 



•50 



•48 ; 

 'bQ 

 •52 



-2 







-2 







-2 

 



-2 

 



-2 

 



58 

 64 

 60 

 65 

 90 

 90 

 78 

 88 

 82 

 85 



•91 

 •92 

 100 

 •89 

 •97 



-4 





 -4 





 -4 





 -4 





 -4 







•94 



•52 



-3 







-3 







-3 







-3 

 



-3 

 



72 

 78 

 80 

 90 

 95 



112 

 90 



112 

 80 

 95 



•92 



•89 



•85 



•80 



•84 

 •86 



-5 





 -5 





 -5 





 -5 





 -5 







30 



88 

 30 

 90 

 26 



90 

 24 



80 

 21 



75 



•34 

 •33 



•29 ( 

 •30 ! 

 •30 ; 



•31 



1 



This curve and others similarly taken with different 

 potentials between and B are shown in PL IX. fig. 4. 



These curves show plainly that the position of the curves 

 is a function of the difference of potential between C and B. 

 Evidently when this perforated box is used, every addition 



