DIELECTRIC CONSTANT OF WATER AT LOW TEMPERATURES. 225 
The author’s experiments were carried out with electrical 
oscillations having a frequency of about 25 millions, pro- 
duced in a Lecher wire system by the oscillatory discharge 
of a condenser. The arrangement of the apparatus is shown 
in Fig. 1. A is a condenser, consisting of two parallel cir- 
Se 
Fig. 1. 
cular brass plates, 30 cms. in diameter, connected to the 
ends of the secondary of an induction coil. This condenser 
is discharged by means of a spark between two aluminium 
knobs immersed in kerosene, and joined to the condenser 
plates by brass rods 3 millimetres thick and 30 cms. long, 
bent into an approximately circular form. ‘Two circular 
brass plates dd’ 8°8 cms. in diameter are held 8 millimetres 
from the plates of A, and attached to them are brass wires 
db,db 0°36 millimetres in diameter and 30 cms. apart, 
except the portions dn, di’, each of length 27 cms., where 
the wires curve in. Two bridges of copper wire, aa’ and 
bb’ are placed across these brass wires. The circuit daa‘d’ 
is called the primary, and ab ba the secondary. 
Across the wires is placed a light wooden slider, the 
Wires passing through small glass tubes attached to it; 
round each of these tubes is a single loop of wire which 
leads to the terminal of a Rutherford detector, the deflec- 
tions produced by which on a magnetometer, are used in 
determining the character of the oscillations set up in the 
wires. The details of the detector and the method of using 
it are similar to those used by Professor Pollock and the 
author in their experiments on Electric Waves in Short 
Wire Systems.’ With the bridge aa at a distance of 170 
-—— ¥ Pollock and Vonwiller—Phil. Mag.,June 19022” 
