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." 189
Thus in Table VIII. will be found the actual length in degrees and minutes of all the
oscillations on the plate. The Roman numerals at the head of the columns indicate the
circles on which the sparks are to be found; the record for each spark is shewn separately.
The mean length of oscillation from the 99 sparks here recorded is 14~ 23'; the range
of the readings is rather over 1~; the means for the various circles are given in the
Table; they range over 17'. It is clear however that the oscillations in any one spark
are not of equal length. As a rule the first oscillation is a long one. This is followed
by one or more of shorter period while, as the spark dies away, the oscillations again
lengthen; the cause of this has been discussed in Part IV.
The lengthening of the latter oscillations is more plainly shewn on some of the other
plates. If we omit the longer oscillations, and take only the more regular central swings
on plate U, we get the following series of numbers, in which the 14~ is omitted for
brevity.
TABLE IX.
Circle... I. II. III. IV. V. VI. VII. VIII. IX.
25 11 25 6 12 26 40 18 41
12 10 18 10 14 23 24 12
17 O 19 5 11 5 36 14 9
9 20 16 38 29 11 10
26 9 14 20 16
23
20
Averages 16' 8 21' 14' 12' 18' 28' 19' 17'
These lead to an average length of oscillation of 14 17'.
In taking the average in this manner we have given equal weight to each
observation.
Now the record of this plate taken at the time of the observation is
PLATE U.
Air condenser in circuit with B coil.
Machine not in circuit but arranged to charge it through a pair of needle points
from a distance so that its capacity should not interfere.