PERIODS OF ELECTRICAL VIBRATIONS. 215 
repetition was practically completed, owing to greater 
accordance among the observations due to the improvement 
in the character of the spark resulting from greater experi- 
ence in the preparation of the spark knobs, two maxima 
close together, were noticed in the plot of the observations 
with one of the straight wires. As the position of the 
maxima could be altered by changing the condenser plate 
distance, the observation pointed to a want of success in 
tuning the condenser and rectangular circuits, an oper- 
ation of considerable difficulty, and threw doubt on the 
accuracy of all the previous work. 
It was decided therefore, after consideration, to do away 
with the hollow boxes attached to the rectangular circuit, 
which complicate the operation of tuning and simply place 
the narrow end of a fixed rectangle near the spark gap of 
the condenser circuit. The tuning of the condenser and 
rectangular circuits now involved only a change of the 
condenser plate distance. This operation was performed 
for three rectangles of different perimeters. It was found 
however, that a want of tune between the condenser and 
rectangular circuits could be better detected by observa- 
tions of the disturbance in the third circuit than of that in 
the rectangle itself. 
The following procedure was finally adopted as giving 
the most definite results:—For a given distance between 
the condenser plates observations are taken of the disturb- 
ances in the third circuit while altering its length by suc- 
cessive steps. This series of observations is repeated for 
various distances between the condenser plates. The plots 
of the observations show the relation between the disturb- 
ance in the third circuit and its length for various condenser 
plate distances. That distance between the condenser 
plates in connection, with which the plot shows the most 
definitely marked maximum, and in which the observations 
