Conductivity of Air enclosed in Metallic Receivers. 309 



a reduction of as high as 60 per cent, being recorded in the 

 case of the freshly cleaned lead cylinder in the third series of 

 measurements referred to above. 



(1) Measurements on hoard steamer 'Corona.'' 



In the first set of measurements a series of observations 

 was made in the laboratory on the conductivity of the air 

 enclosed in a lead receiver which had not been recently 

 cleaned, and the mean of these readings was found to give 

 a value of 41* 7 ions per c.c. per sec. for the conductivity. 

 Measurements were then made on the same day, on board the 

 s.s. ' Corona ' during one of her voyages, and also at a number 

 of points on land on the south side of I ake Ontario between 

 Queenston Heights and Niagara Falls. These results are 

 recorded in Table IX. 



Table IX. 



Comparison of Conductivity Experiments made on 



steamer ' Corona ' with those made on Land. 



" q " = Number of ions 

 generated per c.c. 

 per sec. at 0° C. 



Locality. 



41*7 (mean 



34-9 1 



356 I 



35-2 J 



43-3 



value) 



Physical Laboratory. 



On board ' Corona.' 

 Outward trip. 



Queenston Heights. 



Pavilion, Niagara Falls Park 



Tunnel of Ontario Power Co. 

 42 metres underground.. 



On board ' Corona.' 

 Homeward trip. 



42-4 



420 



35-9 -J 



3o-5 I 



36-5 J 



Mean of results of land experiments = 42*3 ions per c.c. per sec. 

 Mean of results of steamer experiments =55*6 ions per c.c. per sec. 

 Difference =6*7 ions per c.c. per sec. 



From the table it will be seen that the ionization at 

 different points on the limestone soil of the Niagara District 

 was practically constant. It will be seen, too, that the 

 ionization obtained about 42 metres underground at the Falls 

 was practically the same as that obtained at the surface on 

 the limestone ridge. We see also from the figures, that the 



Phil. Mag. 8. 6. Vol. 17. No. 98. Feb. 1909. Y 



