702 



Messrs. McLennan and Burton on the 



in the zinc cylinder at atmospheric pressure are given in 

 column 3 of Table I., the currents being expressed in arbi- 

 trary units, and the times being taken from the closing of 

 the cylinder. 



Table I. 



Time. 



Current : Arbitrary Scale. 



Column 1. 



Pressure.. 501-0 cms. 



Pressure, 74*2 cms. 



Column 2. 



Column 3. 



10 mins. 



30-0 



174 



15 „ 





9-3 



30 ., 



175 



6-2 



•30 „ 



13-2 



■ro 



1-0 hour 



12-0 



— 



1-25 „ 





513 



1-50 „ 



9-9 



— 



175 ,. 



69 



5-1 



2-00 „ 



8-0 



4-9 



4-00 „ 



6-6 



4-8 



5-00 



7-6 







6-00 „ 





50 



1000 „ 





5-8 



22-00 „ 



19-2 







25-00 ., 





60 



29-00 „ 





6-0 



32-00 „ 



220 





34-00 ., 





6-3 



4400 „ 



24-0 



— 



45-00 ., 





6-5 















Fio-. 2 

















i 















, ! ! 





i ' j i 













1 i 





1 ! 





















































! 



I ! 



i 















1 ; ■" 









-] II | 1 1 ! 







<-f 





1 i 









~~---___ 











i/> 1/ 2-t 



JO JJ -to .SS *2 



The ionization curve for these values (fig. 2) shows that 

 the minimum current, 4*8, was reached in about four hours 

 after the air was inclosed. After about eighteen hours the 



