﻿Effect of Clouds on Ionization. 357 



ions present in the steady state under the various fields. 

 This deletion of the ions by the electric field is clearly shown 

 by the numbers in column 4, which gives the current through 

 the clouds obtained by expanding with the field on ; it will 

 be noticed that the effects of the clouds obtained under these 

 conditions are distinctly smaller than the effects of the clouds 

 obtained when the field is off at the moment of expansion. 

 (In fact, in so far as the retarding effect of a cloud produced 

 by a given expansion is a measure of the number of ions 

 caught, a comparison of columns 3 and 4 gives an idea of the 

 number of ions present in the steady state under different 

 potentials with a given intensity of ionization.) 



Table T. 



Eadium in position E t (strong ionization). See figure. 



Expansion 1*32. 



Character of cloud — very dense. Time to fall through 



5 cm. = 90 sees, (approx.). 

 Interval between expansion and unearthing, 3 sees. 



Time of chargiug up, 3 sees. 

 The letters a, b, c, d, attached to the numbers in the 



first set indicate the order in which the observations 



in each set were made. 



Volts on 



Current. 



Current through 

 cloud. No field 



Current through 

 cloud. Field on 



ionization 

 chamber. 



]S T o 



cloud. 



on when expansion 



when expansion 









was made. 



was made. 



- 2 



(a) 132-0 



(c) 132-0 



(b) 27-5 



{d) 28-5 



- 4-5 



212-0 



212-0 



44-0 



49 



- 8-5 



2905 



290-0 



750 



87-5 



- 130 



323-0 



323-0 



1025 



1225 



- 170 



341-0 



341-0 



122-5 



155-5 



- 27-0 



361-5 



361-5 



176-5 



222-0 



- 420 



3700 



3700 



219-5 



2765 



- 84-0 



377-0 



377-0 



287-0 



335-0 



-1220 



379C 



378-5 



313-5 



3495 



-164 



378-5 



378-5 



330-0 



359-5 



-245-0 



379-5 



379-5 



3420 



367-5 



These results are shown graphically in fig. 2. Curve I. 

 gives the currents through cloudless air. Curve II. gives 

 the currents through the clouds of constant density obtained 

 on expansion with no field on ; the field was put on immedi- 

 ately after the expansion so that the steady state was attained 

 well before the quadrants were unearthed. Comparison of 



