Memoirs presented to the Cambridge philosophical society on the occasion of the jubilee of Sir George Gabriel Stokes, bart., Hon. LL. D., Hon. SC. D., Lucasian professor.

DISCHARGE OF AN AIR CONDENSER, WITH A DETERMINATION OF "v." 181
and C as in Fig. 10. A and D being connected together, the frequency rose to 1830;
this result we have not been able to explain as satisfactorily as we could have wished.
Spark
Earth
FIG. 10.
The following may however have been the cause. In the figure A and D are terminals
connected with the outer turns of the coils, B and C those connected with the inner.
Now the capacity of the outer turns is greater than that of the inner, while at the same
time the portions of the coils which are nearest to the condenser, and in which therefore the potential difference is the greater, will have most effect on the result. We
have however taken an average value of S', 16/30, in calculating the correction. It may
be that this average is right for Fig. 9, but that for Fig. 10 it ought to be reduced,
for the actual value of S' near C is only 3/5 of that near A. If we assumed
= 3 x 16/5 =10 say, or S' =10/30, we should obtain as the frequency the value 1860
which agrees closely with that given by experiment.
Again on July 30 the cylinder condenser was connected to the coil as in Fig. 11.
The observed frequency was 2560.
s ' Spark
D
Earth
FIG. 11.
The calculated frequency for this case, assuming the corrections already given, is
2060, or if we assume the connexions to have been as in Case ii., 2270; in either
case the result is much too low.
It will be noticed however that in Fig. 11 the condenser is connected to the
terminals B and C, i.e. to the inner terminals of the coil as in Fig. 10, and we have
just seen that the assumption that the effective capacity of the coil is 10 metres
when this is the case serves to reconcile theory and experiment. It becomes of interest
then to evaluate the frequency, assuming S~ equal to 10 and S' to 10/30.