﻿48 Mr. Norman Campbell on Delta Rays. 



changes in the apparatus made it impossible to reproduce 

 accurately the results of a series of measurements ; these 

 results seem to some extent a function of the exact form of 













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the apparatus. It is to be noted that the curve for soot is 

 considerably flatter than that for any of the metals. Indeed 

 the difference between soot and the other materials is really 

 greater than appears from the figure ; for in the figure all 

 the values of the current are expressed as ratios of the 

 current for a potential difference of 40 volts, and, while the 

 current for the metals is completely saturated for that 

 potential difference, the current for soot does not become 

 saturated until the potential difference is nearly 80 volts. 

 If the curve for soot were, like that for the metals, referred 

 to the maximum ordinate as unit, it would appear even 

 flatter. 



The further discussion of these observations will be post- 

 poned for the present. 



3. Experiments were next tried, similar to those described 

 in § 15 of the previous paper, in which the lower electrode 

 (A) was covered with soot, while the upper electrode (B) 



