100 



Bumstead and Wheeler — Radio-active Gas. 



m 



A cylindrical condenser (fig. 3), 37 cm high and 12*5 

 diameter, was made of heavy galvanized sheet-iron with rings 

 of planished brass, A, and A', soldered to flanges at top and 

 bottom ; at the top, the guard plate, B, rested upon a rubber 

 gasket and was bolted to A by eight small bolts provided with 

 ebonite bushings so that the cylinder was insulated from B, 

 which was kept earthed. The central rod, C, passed through an 

 ebonite collar, D, and the joints about the collar were carefully 

 made tight by sealing-wax. At the bottom, the brass plate, E, 

 was similarly bolted to A' with a gasket between, but no bush- 

 ings were needed in this case, and the heads of the bolts were 



counter-sunk in the bottom surface of E ; this plate had a hole 

 in the middle, and above it the porous plate, F, was fastened 

 with sealing-wax. Another plate, G, also provided with a gas- 

 ket, was clamped below this by eight small iron screw clamps, 

 so that it could be easily removed at any time and the porous 

 plate exposed. The connection to the electrometer was a brass 

 rod supported by ebonite in a rectangular brass box, H, with a 

 hinged lid ; this box rested on the guard plate, B, and on the 

 case of the electrometer, and two holes in its bottom admit- 

 ted .the binding screws of rod in the cylinder and of the electro- 

 meter. Ordinarily the rod and pair of quadrants connected to 

 it were earthed by N, which was hinged to the box and rested 



