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." 177
It would be tedious to quote at full length the details of all the preliminary spins,
and indeed all of the records have not yet been read. But such as seemed likely to
be instructive were carefully examined, and a summary of them is given below.
July 25. The l1-plate disc condenser arranged so that the machine charges it
through a needle point, an inch or two distant, without direct contact. The needle
point replaces the wooden connexion previously used. The following are the lengths of
various half oscillations as recorded on a plate spinning 64 turns a second: 4~ 42',
4042', 4~47', 4041', 4 49', 4 41', 4~44', 4 38', 4 38', 4~ 41, 4~ 50', 4~ 48', 4~ 37', 4043',
4~ 38', 4~29', 4~19'. Average of these numbers 4~40'.
Frequency deduced from the observation, 2470 per second.
Same date. Cylinder condenser, similarly arranged. Frequency 2370.
Same date. 5-plate disc condenser, similarly arranged, average 4~ 30'. Frequency 2580.
July 30. Cylinder condenser arranged in a different part of the circuit, viz. each set
of plates connected to one of the terminals of the two halves of the coil as in Figure 11,
p. 181.
Average reading 4~ 34'. Frequency 2560.
On other circles of the same plate, condenser detached and middle terminals of coil
left insulated, so that the only capacity was that of the two halves of the coil:
Readings 2~45', 2 54', 2~31', 2~4', 2~4', 2~2'.
Average 2~ 30'. Frequency 4630.
July 31. Spins taken at the 12-pattern speed (i.e. 21~ revs. per sec.) with the large
Muirhead condenser in simple circuit with the whole coil. The outer circle was taken
with the condenser attached to middle screws, as on July 30; for the others it was connected in the ordinary way. But no correction for coil or other capacity should be needed
with this great condenser.
Average reading 30~ 30', the speed not perfectly steady.
Frequency deduced 126 per second.
August 1. Cylinder and disc condenser in parallel.
Average of readings for spark alternations on outer circle 6~ 32'... for another set ditto....6~ 38'
",, for spark on second circle.. 6~ 30',,," for another set ditto.... 6~ 29' 5",,,, for spark on third circle...6~ 32'... for another set third circle.. 6~ 29'
". " for spark on fourth circle...6~ 30'
General average for this plate...... 6~ 31' 5"
Frequency deduced, 1766.
The speed for the outer circle was steadiest.
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