Conductivity of Air enclosed in Metallic Receivers. 305 



results, but if the precautions mentioned are taken, it is 

 possible to obtain a thoroughly reliable value for the con- 

 ductivity of air enclosed in any metal receiver. 



(b) Daily Variation in the Conductivity of Atmospheric Air. 

 Among other investigators, Wood and Campbell*, 

 McKeon f, and Strong J have observed daily variations in 

 the conductivity of air confined in metallic vessels; and in- 

 asmuch as it was not practicable to take observations in 

 different localities at the same time of day in the present 

 investigation, a preliminary set of observations was made 

 throughout different days in a room in the Physics building, 

 on the conductivity of the air confined in a lead receiver, 

 in order to obtain evidence of the daily variation, and also, if 

 such existed, to obtain an estimate of its magnitude. 



Table VI. 

 Lead Cylinder 1, in steady state. — Voltage on Cylinder -f 83. 





q = number of ions 



Time. 



per c.e. per sec. 





reduced to 0° C. 



Dec. 24th. 





10.23 a.m. 



22-48 



10.43 



22-51 



11.10; 



22-54 



11-32 



2245 



11.55 



21-74 



12.15 p.m. 



22-73 



12.40 



21-96 



1.00 



22-94 



Dec. 26th. 





9.35 a.m. 



22-44 



9.58 



21-86 



10.20 



21-87 



10.45 



22-25 



11.05 



22-96 



11.28 



22-79 



11.50 



2253 



3.55 p.m. 



22-65 



4.15 



22-54 



4.40 



22-94 





Mean 2245 







Two sets of continuous readings taken in this way with 

 the air in a lead cylinder in the steady state mentioned 

 above, are given in Table VI., and from the values quoted it 



* Wood and Campbell, Phil. Mag. Feb. 1907. 

 f McKeon, Phys. Eev. Nov. 1907. 

 t Strong Phys. Zeit. Feb. loth, 1908. 



