502 
MR. H. A. WILSON ON THE ELECTRICAL CONDUCTIVITY 
stretched across and kept in position by two brass strips screwed dowm over the slots. 
The gauze was thus stretched across the under side of the upper disk. The gauze 
had a mesh 0'06 centim. square, with wire 0'02 centim. thick. It was found necessary 
to use a wider mesh for the lower electrode to allow the flame to pass easily. The 
grating on the lower disk was, therefore, made by winding platinum wire between 
F, 
Flame. 
Q, Quadrant electrometer. 
D, 
Wood block. 
C C', Commutators. 
T, 
Flame tube. 
G, Galvanometer. 
E E', 
Electrodes. 
V, Voltmeter. 
E'„ 
E„ 
Upper surface of upper electrode. 
Upper surface of lower electrode. 
B, Battery. 
small brass pegs flxed in the upper surface of the disk. The wires were 0'3 centim. 
apart. 
The lower electrode was connected through a galvanometer to one pole of a battery 
of small secondary cells, and the upper electrode was connected to the other pole. 
The flame fuhe was also connected to the same pole of the battery as the lower 
electrode. The jiotential difference between the two electrodes could be measured by 
means of a multicellular electrostatic voltmeter when it was above 250 volts. A 
