PERIODS OF ELECTRICAL VIBRATIONS. 221 
diameter; the increase of inductance due to replacing 5 
ems. in the central part of the circuit by the fine steel wire 
Seems to have been negligible. 
It has been found in this research more difficult to work 
with the longitudinal detector than with the solenoidal one. 
The former requires more delicate handling and a more 
sensitive magnetic arrangement for detecting changes of 
magnetisations. 
The experiments have been carried out in a room 10 
metres long by 6 metres wide, bare with the exception of 
gas and water pipes around the walls. 
The Physical Laboratory, 
The University of Sydney, 
November 25th, 1903. 
APPENDIX. 
THE HFFECT or CAPACITY atv THE ENDS OF a 
CIRCULAR RESONATOR. 
By J. C. CLosE, Deas-Thomson Scholar in Physics. 
WITH a Similar apparatus to that described in the preceding 
paper, but of smaller dimensions, the vibrations connected 
with open circular resonators were compared with those — 
of a narrow rectangular closed circuit. The resonators 
were made of copper wire 0°33 cms. in diameter, and the 
wire was in all cases 152 cms. long. The rectangle was 
made of thin brass wire 0°04 cms. thick, the width of the 
rectangle being 31 cms. The experiments were made by 
the first method described above, in which the length of 
the resonator is kept constant, the length of the parallel 
wires being altered by winding the wire into the little boxes. 
In an experiment, the length of the parallel wires was 
altered by steps of 5 or 10 cms. and readings taken of the 
disturbance in the resonator on discharging the condenser 
with a Rutherford solenoidal detector. The observations 
