77(3 Prof. J. C. McLennan on the 



With cylinder No. '2 thoroughly cleaned in the manner 

 already described, a reading of 54*5 divisions per minute 

 with but slight variations was regularly obtained with freshly 

 filtered air. With this cylinder, too, when the air was un- 

 disturbed in it the conductivity steadily rose, and after a 

 time approached a maximum value. The time required for 

 the steady state to be reached was, however, much greater 

 than with cylinder No. 1. 



A set of readings which exhibit this rise are given in 

 Table VIII. and a curve representing them is shown in 

 fig. 2. 



Table VIII. 



Lead Cylinder No. 2. 



Conductivity 

 Time. (Arbitrary Scale). 



June 5 ... 54-6 



7 58-3 



9 61 



12 62 



15 63-2 



17, 5 p.m 64 



Filtered air was now blown through cylinder 

 for twenty minutes : 



June 17, 5.30 p.m.... 606 



18, 1.00 p.m.... 64-4 

 27, 10.30 a.m. ... 67 



Filtered air again blown through for 

 twenty minutes : 



June 27, 12.30 p.m. ... 62'4 



Filtered air blown through for one hour: 



June 27, 3.30 p.m.... 62'8 



From this it will be seen that when fresh air was intro- 

 duced into the cylinder on June 17 the reading dropped from 

 64 to 60*6, and again on June 27 the introduction of fresh 

 air was followed by a drop from 67 to 62*4. Air was then 

 drawn through the cylinder for one hour, but no further 

 drop in the conductivity ensued. When similar observations 

 were made on other occasions with this cylinder similar 

 results were obtained. After a rise occurred, the introduc- 

 tion of fresh air was always followed by a drop in the 



