226 O. U. VONWILLER. 
cms. from nn’, the wooden slider carrying the detector being 
5 cms. from an’, the capacity of A was altered by varying 
the distance between the plates until the primary was in 
resonance with the condenser vibration; the deflection 
produced by the detector being a maximum when this is 
the case. The effective length of the primary is now 4/2, 
where 4 is the wave length of the condenser radiation. 
By altering the position of the bridge bb’ the secondary 
can be brought into resonance with the primary, this being 
the case when its effective length is 4, the correct position 
being determined by keeping the slider midway between 
the two bridges, i.e. at a loop of the wave, and altering the 
length of the circuit until a maximum deflection is obtained. 
In these experiments a condenser C was placed across 
the wires at some place cc’. The effect of this capacity is 
equivalent to an addition to the length of the wires, the 
wave length of free vibrations in the circuit abb’a’ being 
given by 4 in the equation— 
cot =e + cot a 
as is shown by W. B. Morton,’ a and b being the distances 
from the middle points of the bridges aa and bb’ respectively 
to the condenser, C being the capacity of the condenser and 
s the capacity per unit length of the two parallel wires. If 
the secondary is in resonance with the primary, a change 
in the capacity of C will throw it out of resonance and the 
deflections produced by the detector will be smaller. 
WY 745 
Pes 
An investigation of Morton’s formula shows that a given 
percentage change of capacity produces the greatest pro- 
portionate change in the effective length of the circuit 
when a=b = X/8, the effect of the capacity being thus 
equivalent to an addition of 4/2 to the length of the circuit. 
It has always been observed however, that when the 
1 W. B. Morton—Phil, Mag., May 1897. 
