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.

194 MESSRS GLAZEBROOK AND LODGE, EXPERIMENTS ON THE OSCILLATORY
Coil B.
Plate J U
Number of sparks 28 37
Length of wave 14~ 26' 14~ 20'
Mean length of wave 14~ 22'.
From these we find as the mean length of the wave when the complete coil
A+B is used 26 11'.
With regard to the observations made with the coils A and B in circuit separately,
it will be observed that plates H and J give higher results than the others. Now
there is a note in the book that for these two series the outer plates of the
condenser were earthed; they were taken therefore under different conditions to the
others; if they be omitted we have as the mean wave length for plate A 14~18',
and for B 14 20'; if we include plates H and J, the mean for A is 14~ 20' and
for B 14 22'.
The corresponding frequencies are, excluding plates H and J,
for coil (A + B) 880 per second,
for coil A 1611 per second,
for coil B 1607 per second.
If we take the whole series of sparks for A and B we get respectively for A
1607, and for B 1603.
While the frequencies given by plates H and J are
for A 1583,
and for B 1595.
It is hardly necessary to work out the frequencies for each plate. For the complete
coil A +B the greatest variation from the mean is four parts in one thousand.
We may now determine from these spark records the value for " v."
We have the formula
v= 27r. frequency x k/ k L
where k is the constant, the values of which are given in Table V., occurring in the