
Electrical Vibrations associated with Simple Circuits. 651 
judged the same for all. Hundreds of observations have been 
rejected on account of irregularity of the spark. On the 
other hand, hundreds of discharges, where the sparks looked 
pertect, have given results utterly non-accordant. 
For the earlier of these experiments the sparks passed 
between aluminium spheres 1 cm. in diameter. The spheres 
were constantly repolished and were immersed in a large bath 
of paraffiin-oil kept well stirred. A considerable improvement 
resulted on replacing the aluminium spheres by - small 
spheres of platinum made by rounding the ends of pla- 
tinum wires 0:13 cm. in diameter in the oxyhydrogen 
flame. With a flame not too hot and with patience, little 
hemispheres can be finally obtained on the ends of these wires 
whose surface and figure seem to leave nothing to be desired. 
About 30 sparks can in general be taken from such ends, 
though many more in some cases before they require to be 
re-fused. In some few instances series of observations have 
been obtained accordant among themselves, but differing from 
another series with the conditions unaltered. This has been 
due no doubt to the apparently chance nature of the character 
of the spark. No result has been retained which has not been 
fully confirmed by repetition. 
The Detectors.—For the majority of the observations, and 
particularly for the final ones, Rutherford’s solenoidal detector 
has been used. In the later experiments with straight wires 
where the length of the wire is altered, keeping the loops of the 
fine wires attached to the detector at a fixed distance apart on the 
straight wire, as described above, tends to increase the reading 
for shorter lengths. Such action has been found not to affect 
the result. In the experiments with open circles, the loops 
of the detector-wires were always at the ends of the circular 
wire, and in those with closed circuits always at the ends of 
a diameter at right angles to the long side of the rectangular 
circuit. 
To show that the length of the detector-wires does not 
influence the result of an experiment, the following trials 
were made with a straight wire :—(1) The wires to the 
detector, each 100 cms. long, once looped round an insulating 
tube on the straight wire; (2) wires each 40 cms. long 
soldered to the straight wire ; (3) wires 25 cms. long soldered 
to the straight wire ; (4) wires 10 ems. long soldered to the 
straight wire. In each case the observations gave the same 
result, the straight wire 400 cms. long being in tune with a 
rectangle 955 cms. in perimeter. 
Further, an exhaustive comparison has been made between 
the results given by the solenoidal detector and those obtained 
with Rutherford’s longitudinal detector. The latter was made 
