Earth- Air Electric Cur rents. 



the glass tube. The trap consisted of a closed brass tube 

 fitting over the pipe which communicated from the upper to 

 the lower parts of the vessel C. A hole was made in the 



Fig. 1. 



a(r 



Sfa 



1 



TO CXPO'CD PLATE 



TO ELECTROMETER 



covering tube somewhat below the level of the top of the 

 communicating tube, so that the dust which floated on the 

 top of the water in the upper part of C, and the grit which 

 sank to the bottom, could not pass into the glass tube. 



