Radioactivity of Lead and other Metals. 



71 



therefore 14'22 would be the total number generated per c.c. 

 per second by the combined radiations. In the same manner 

 it can be shown, by taking Eve's value of 5 3' 7 per cent, as 

 representing the amount of secondary radiation excited in a 

 zinc radiating surface compared with that obtained with a 

 lead one, that 17*88 is the number of ions which should be 

 generated by the penetrating radiation from the earth, and 

 by the secondary rays excited by these in each cubic centi- 

 metre of air enclosed in the zinc cylinder No. 8. 



Table VI. 



Column 1. 



Column 2. 



Column 3. 



Column 4. 



Column 5. 



Column 6. 







bD 



©■§ 



^3 i T3 en* o 

 <a § p ^ = O 



1 CG 







■_j3 "£ 



"^ ^ 



CO 4) ^ ?• f -1 



p,;*2 — 







;- <U 



S i , 



S ft 5 ' 3 6 



o S-. o 







1* 



iflg 



s (D c z: r- >! 



^.2 



Cylinder 



Metal. 



a_ i — 



O o 



.2 u 



■2-*gg.-g 



> o 



No. 





^2 





No. of 

 c.c. pei 

 n g rays 

 ed se 

 culated 

 e impu 



5 c -Q 







3 % 



p-l 



I'll 



1 UTSo'l 





1 



Lead 



1536 



23 



23 





2 



,, 



16-29 



160 



22-77 



137-23 



3 





9 36 



37 



24-63 



12-37 



4 



;> 



11-2 



78 



24-15 



53-85 



o 



" 



12-92 

 10-12 



34 

 55 



23-67 

 24-42 



10-33 

 30-58 



6 



7 



>} 



1323 



61 



23-58 



37-42 



8 



Zinc 



462 



15 



17-88 





9 



Aluminium 



•23 



15 



1422 



•78 



Calculations similar to the above have been made on the 

 number of ions which, on the basis laid down, should be 

 generated per c.c. per second in the air enclosed by each ot 

 the lead cylinders, Nos. 2-7, and the deduced values are all 

 recorded in Column 5 of Table VI. With cylinder No. 9 

 the calculated value and that found experimentally present a 

 good agreement; but with cylinder No. 8 the calculated is 

 slightly greater than the observed value, and may be due to 

 our making too high an estimate of the ionization produced 

 by the secondary rays from the zinc walls. Eve states in 

 his paper that he found the secondary radiation came not 



