92 



ROYAL SOCIETY OF CANADA 

 TABLE IV. 



III. — Some Special Observations with Lead Cylinders. 



It will be remembered that Prof. McLennan in his investigation 

 ot last year drew the conclusion that ordinary commercial lead, in so 

 far as he investigated it, contained in general an active impurity. Such 

 being the case, one should expect a certain falling olï in the course 

 cf time of the ionization in a lead receiver due to the decay of the 

 activity. It was decided then to determine again the conductivity of 

 air in certain lead receivers used by him in June last in liis investiga- 

 tion to see whether any decrease from the former values could be 

 notefl. Lead cylinders, described as numbers 1, 2 and 3 in Prof. 

 McLennan's paper, were used for this purpose, and the values of the 

 ionization for each cylinder determined with both the electroscope and 

 the electrometer. These numbers, which are given in Table V, show 

 a considerable decrease in the value of " q " from the values for each 

 receiver obtained by Prof. McLennan. 



