[mclennan-murray] residual IONISATION IN AIR 111 



radiations traversing it which are emitted by the wails of the contain- 

 ing vessel, and by the land, the atmosphere, and the water in the 

 neighbourhood of the enclosed air whose conductivity is being meas- 

 ured. 



We desire here to acknowledge the services of Mr. P. Blackman, 

 Mr. T. Plaskett and other members of the mechanical staff in the 

 Physical Laboratory for assistance in carrying out the investigation 

 under rather trying circumstances. 



The Physical Laboratory, 



University of Toronto. 

 May 1st, 1915. 



