186 Dr. H. A. Wilson on the Electric Intensity/ 



we get 



_ Pav2(vi + V2) 

 '~ ^ AffW' 



Now v^ is known to be very small coii^pared with V2 at low 

 pressures, and so may be neglected; also V2 = k2X, and 



«=#(-) 



_ ek2^X.^p 



4f)- 



hence 



This equation may be written 



where C and B are functions of p only. 



In the following tables the observed values of X are 

 compared with those calculated by means of this formula, 

 taking appropriate values for C and B, and using Townsend's 



values of /( — ) taken from the curve on page 212, Phil. Mag. 



Feb. 1901. 



The fourth column contains values of the current calculated 

 by means of the formula from the values of X in the first 

 column. The last column contains the values, of X taken 

 from the experimental curves for the calculated values of 

 the current. 



Table IV. 

 p=0-m7. C=3-69. B=4530. 



X. 



X 



'& 



I (calculated) 

 1 = 10-9 ampere. 



X (found for 

 calculated value of ^). 



1 

 54 



81 



053 



3-5 



54 



1 57 



86 



0-60 



5-6_ 



58 



i 60 



90 



070 



10 



60 



63 



95 



0-77 



22 



63 



66 



99 



0-86 



77 



65 



67 



101 



0-88 



364 



67 



