212 J. A. POLLOCK. 
EXPERIMENTAL DETAILS. 
Three methods have been used in this investigation. In 
the first a condenser C with a discharge circuit aa, is 
arranged as indicated in Fig. 4, the diagram not being 
drawn to scale. 
The condenser plates are attached to wooden stands, one 
of which can be moved by ascrew, the two condenser plates 
always being strictly parallel. One of the discharge wires 
is cut and connection remade through a pool of mercury. 
This enables the condenser plates to be set at any distance 
from each other without disturbing the spark gap s. Two 
small hollow boxes bb, are placed close to the condenser 
plates. The boxes are provided with pegs which can be 
turned from the outside. To these pegs parallel wires are 
attached, the wires coming out through holes in the sides 
of the boxes. This arrangement of wires leading into 
hollow boxes was used by St. John,’ and it enables the 
length of the wires to be conveniently altered without 
changing the capacity of the system near the condenser 
plates. The wires are bridged at their ends and at some 
other point as at e. Ata distance of 1 cm. from the ter- 
minal bridge is placed a third circuit f, whose vibration 
1 §t. Jonn—Phil. Mag. 38, 1894. 
. 
P 
f 
: 
E 
