922 J. A. POLLOCK. 
with the detector were plotted against lengths of rect- 
angular circuit and a curve drawn freely through the points 
obtained. The crest of the curve has been taken as marking 
the length of the rectangular circuit when in tune with 
the open circle. 
The sparks which discharged the condenser took place 
between aluminium spheres immersed in paraffin oil. In 
spite of the fact that the discharge surfaces were kept well 
polished the sparks were not uniform in character; this 
accounts for the variations in the readings. At least two 
sets of observations were taken in determining the position 
of each crest. A specimen curve is given in Fig. 6. 
