enitaul Vibrations associated with Simple Circuits. 649 
curves drawn from observations obtained as just described. 
Once the circuits are tuned, the series of observations, 
necessary for a determination of the length of a third circuit 
when in tune with the rectangle, need only be repeated until 
the chance of a fortuitous accordance of the observations is 
eliminated. 
Typical examples of the curves obtained are given in fig. 5. 
The ordinates represent the difference of reading in cms. of 
the deflexions caused by the detector before and after de- 
magnetization ; they are proportional to the magnitude of the 
disturbances in the third circuit. Abscissee represent the 
length of the third cireuit, observations being usually taken 
for successive lengths differing by 20 cms. As the demag- 
netization of the detector depends, cwteris paribus, on the 
length of the spark, such curves are only wholly comparable 
when they represent observations taken with the same 
spark-gap. 
In fig. 5, curve 1 is a plot of observations taken in con- 
nexion with one of the straight wires, using the solenoidal 
Fig. 5. 
Stradi A wire 
Max. for lenglh | ak for ler 
520 cms. Ab0c 

detector. Curves, 2, 3, and 4 refer to the case of one of the 
open circles. They are the plots of series of observations, 
without alteration of spark-gap, taken with condenser-plate 
distances successively increased by 0°1 em., the solenoidal 
detector being used. For tuning the condenser and rect- 
angular circuits thirteen such curves were obtained, the series 
being extended and repeated three times to avoid any chance 
accordance of the observations. Curve 5 is a plot of observa- 
