Imclennan-mcleod] EARTH'S PENETRATING RADIATION 



29 



Let now Av be the loss in voltage per hour with the tube s.s. up 

 and Av, with it down. 



Then if C is the capacity of the system 



Q 



C Av 



300 X 3600, 



I.e. 



1-04 Av 

 300 X 3600 

 1-04 Avi 



in the present case. 



and Q, 



* 300 X 3600 



From this it follows that B is given by 



1-04 (Av— AvJ 



B 



300 X 3600 (V — Vi) 



Finally the number of ions generated per sec, per cc. if saturation 

 voltages are used is given by 



B 



N 

 i.e. N = 



-where e is the charge on an ion. 

 1-04 (Av— Avi) 



300 X 3600 (V — Y^) e 



or if V be taken as 2021-1 cc. V^ as 31-5 cc. and e 

 in electrostatic units 



N 



1-04 (Av— Av,) 



300x3600. (2021-1 —31-5) X 4-75 X 10 

 or N = 1-02 (Av— Av,) 



4-75 X 10 



10 



10 



i.e, the number of ions generated in the receiver per cubic centimetre 

 per sec. is equal to 1-02 times the difference in the drops in voltage 

 per hour observed with the tube s.s. up and down. 



TABLE I. 



A set of readings taken with instrument at Cambridge, England, 

 is given in Table I, and a curve representing them is shewn in Fig. 2. 



