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ROYAL SOCIETY OF CANADA 



It would seem from these observations, therefore, that very little 

 diurnal variation exists in the penetrating radiation at Toronto. 

 Wright's observations, however, were extremely limited in number and 

 it was decided to extend them, to ascertain whether it would be neces- 

 sary to modify in any way the conclusions which might be drawn from 

 them. The following paper contains an account of these observations 

 and it will be seen from the results that they point quite definitely to 

 the absence of anv regular diurnal variations. 



II.— APPARATUS. 



The measuring instrument used was the latest type of Wilson 

 gold-leaf electroscope, and the arrangement of apparatus adopted is 

 shewn in Fig. 1. The case of the electroscope was joined to earth and 

 the leaf system to an electrode which passed up into the ionising 

 chamber 11. This chamber was insulated from the electroscope case, 

 and could be charged as desired by means of the battery B to any 



