PERIODS OF ELECTRICAL VIBRATIONS. P19 
were constantly repolished and were immersed in a large 
bath of paraffin kept well stirred. A considerable improve- 
ment resulted on replacing the aluminium spheres by small 
spheres of platinum made by rounding the ends of platinum 
wires 0°13 cms. in diameter in the oxyhydrogen flame. 
With a flame not too hot, and with patience, little hemi- 
spheres 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 refused. In some few instances series of 
observations have been obtained accordant among them- 
selves, 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 bas been used. In the later experiments with 
straight wires, where the length of the wire is altered, 
keeping the wire attached to the detector loops at a fixed 
distance apart on the straight wire as described above, 
tends to increase the reading for shorter lengths. Such 
action however, 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 
infiuence 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 
