Conductivity of Air enclosed in Metallic Receivers. 297. 



at a number of points in the neighbourhood o£ Toronto, both 

 on land and over the water of Lake Ontario; and it was found 

 that while a uniformly low and steady value was obtained 

 for the conductivity over the water at all depths beyond a 

 few metres, values varying over a wide range were obtained 

 for the ionization, in measurements made on land at different 

 places and on different soils. 



The lowest values for " q" the number of ions generated 

 per c.c. per sec. in air confined in the metallic cylinders, were 

 obtained in measurements on the surface of the lake and on 

 the top of large masses of sand on the lake-shore. With a 

 lead receiver under these circumstances the value S'6 ions 

 per c.c. per sec. was obtained for " q" and with zinc and 

 aluminium cylinders under the same conditions the values 

 6*00 and 6*55 respectively. These values, it will be seen 

 from Table L, are considerably below those hitherto recorded 

 for the conductivity, obtained under any circumstances, of 

 air contained in closed metallic receivers. 



Table I. 



Receiver. 



Observer. 



</• 



Conditions. 



Lead 



Zinc 



Eve 1 . 



>» 

 H. L. Cooke 2 . 



McLennan 3 . 



;; 



Wright. 



„ 



96 

 24 

 24 



136 



91 



23 



15 



15 



8-6 

 60 

 6-55 



} Observations in Physical 

 I Lab., McGill, Mon- 



Aluminium ... 

 Brass 



Lead 



Zinc 



J treal. — Unscreeened. 



Unscreened. 



Screened by large masses 

 of lead. 



Observations taken in 

 basement of Univer- 

 sity Library. McGrill. 



~\ Unscreened. 

 1 Measurements made in 

 f old Physics department . 

 J Toronto University. 



\ Measurements made over 

 the surface of Lake 



Aluminium ... 



Lead 



Zinc 



.Aluminium ... 



Ontario. — Receivers 

 I otherwise unscreened. 



1 Eve. Phil. Mag. Sept, 1906. 



a H. L. Cooke, Phil. Mag. vi. p. -103 (1903). 



3 McLennan, Phil. Mag. Dec. 1907. 



