198 To J. A. POLLOCK, | 
A COMPARISON oF THE PERIODS OF THE ELECTRICAL 
VIBRATIONS assocIATED WITH SIMPLE CIRCUITS. 
By J. A. PoLLock, Professor of Physics in the University 
of Sydney, 
With an Appendix by J. C. CLosz, Deas-Thompson Scholar 
in Physics. 
[Read before the Royal Society of N. S. Wales, December 2, 1903. ] 
INTRODUCTORY. 
THE object of the present research has been to compare 
the periods of the electrical vibrations connected with 
narrow rectangular closed circuits with those of the oscil- 
lations associated with straight wires and with open and 
closed rings. The essential features of the experimental 
method are as follows :—A condenser is discharged in the 
neighbourhood of a narrow rectangular closed circuit; 
oscillatory currents are thus set up inthe rectangle which 
in turn induce: others in a third circuit of required shape. 
Observations of the amplitudes of the disturbances in the 
circuits are made with Rutherford’s magnetic detectors, 
while the dimensions of the circuits are adjusted, step by 
step, until finally all three are in tune. The length of 
a circuit of any shape can thus be found which has the same 
period of electrical vibration as that of a given narrow 
rectangular closed circuit. 
When the experiments were commenced, it was generally 
considered on theoretical grounds, that the wave length of 
the free oscillation connected with open resonators was 
equal to twice the length of the circuit,’ and certain experi- 
1 Kirchhoff, Poggendorf’s Annalen 121, 1864. Thomson, “ Recent 
Researches,”’ p. 340, 1898. Poincaré, ‘* Les Oscillations Electriques,” p. 
237, 1894. 
