62 



Prof. J. C. McLennan on the 

 Table I. 





Material of 



cylinder. 



Length 60 cm. j 



Diameter 24 cm. 



Thickness 



Average No. 





No. 



of Bheet 



of ions per c.c. 



Remarks. 





in mm. 



generated 











per second. 





i .-... 



Lead 



1-85 



23 



This sample was taken 

 from a sheet of lead' 



















which bad been used as 1 











a lining in a case in- 











stalled in the Univer- 











sity over twenty -eight 1 











years ago. 



1 



Lead ' 



2-25 



160 



Commercial English' 

 sheet lead obtained 

 from the lead works at 

 Toronto. 



3 



Lead 



14.5 



37 



Commercial English 

 sheet lead selected 

 from a different ship- 

 ment from No. 2. 







1-85 



78 



This sample was ob- 

 tained from a sheet 













rolled from an old pipe 



i 



• 







which had been used 



i 









as a drain for 25 or 











30 years, and was after- 











wards melted down. 



i 5 



Lead 



1-80 



34 



' Rolled from a pig of 

 1 lead recently received 













1 from the smelter at 





| 







! Trail, B.C. Canada. 



6 



Lead 



1-80 



55 



j Rolled from English 

 ! pig lead ; Quirk and 

 Bartons. 



7 



Lead 



1-80 



61 



Rolled from English 

 i pig lead. Cookson's. 



8 



Zinc 



1-62 



15 



Commercial sheet zinc. 



9 



Aluminium... 



•41 



15 



Commercial sheet alu- 

 | minium. 



With cylinder No. 5 the value obtained for "q" was 34 

 ions per c.c. per second. This lead, we have reason to believe, 

 was mined not more than two or three years ago, and under 

 the circumstances might have been expected to show a much 

 higher activity. Its activity, however, was practically the 

 same as that of No. 3, which was selected at random from a 

 commercial sheet of lead which probably had been on the 

 market for some years. 



Cylinders No. 6 and No. 7 possessed a moderate activity 

 compared with the others of the same metal. The number 

 of ions per c.c. generated in air per second with them being 

 55 and 61 respectively. 



With cylinder No. 2 the greatest ionization was obtained, 

 the value of " q J? in this case being 160 ions per c.c. per second. 



