652 Mr. J. C. Close on the Effect of Capacity 
of a piece of pianoforte steel wire 5°5 cms. long which had 
been dissolved in acid until its diameter was 0-014 em. The 
ends of the steel wire were soldered to two pieces of copper 
wire each 1 cm. long and 0°33 cm. in diameter. The wire 
was then firmly fixed by means of the copper ends in a glass 
tube, the copper pieces projecting a few millimetres beyond 
the ends of the tube. In an experiment the detector, after 
being magnetized to saturation, replaced a similar length cut 
trom the middle portion of the circuit under investigation. 
Connexion was made by amalgamating the copper ends which 
were in contact, excess of mercury always being present. 
The magnitude of the disturbance in ike third circuit is 
estimated by its demagnetizing effect on the steel wire, the 
detector being placed after magnetization and demagnetization 
in a geometrical clamp with one of its poles close to the 
magnet of a magnetometer. 
The results obtained with the longitudinal detector, in no 
less than 16 cases, are identical with those found with the 
solenoidal one, showing that the demagnetizations of the core 
of the latter are not affected in the present instance by any 
_ vibration peculiar to the detector circuit. This point has also 
been considered by Chant (Am. Journ. Sci. xv. p. 54, 1908). 
The circuits examined have been made of copper wire 
0°33 cm. in diameter; the increase of inductance due to 
replacing 5 cms. 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 
magnetization. 
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 round the room. 
The Physical Laboratory, 
The University of Sydney, 
November 25th, 1903. 
APPENDIX. 
The Effect of Capacity at the Ends of a Circular Resonator. 
By J. C. Cuosz, Deas- Thomson Scholar in Physics. 
With a similar apparatus to that described on p. 646 of 
the above 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 cm. in diameter, and the wire 
was in all cases 152 cms. long. The rectangle was made of 
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