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." 151
TIME OF SWING OF NEEDLE.
The time of swing was found in the usual way by observing the transits of the
zero reading over the cross-wire of the telescope.
In this case 12 transits were observed and then after waiting for an interval of
16 transits 12 more were taken.
We thus found the mean of sets taken on several occasions, always both before and
after the series of throws and deflexions; T=10'713 mean solar seconds. The time was
taken on the chronometer already mentioned in Part I. of the paper.
The greatest error from the mean in any one of the 12 observations was less than
2 parts in 1000. Thus the time of swing is very accurately known.
The value of X was found by reading a series of 42 deflexions. The average value of
a large number of observations (which lay between '0134 and '0131) was '01324.
From these observations we obtain for the value of L
L = 4-6488 Legal Quadrants.
The result requires a small correction because $Q was at 17~'5 instead of at 17~
at which the box is right.
Introducing this we find as the value
4'6494 Legal Quadrants.
Four sets of observations were taken on the two coils arranged in series.
Table III. gives the details, from which the results have been calculated. The
mean value of '01324 has been employed throughout for the logarithmic decrement X.
TABLE III.
Tempera- a c T Q P L L
Date ture c T QP L t7
ture at 17~ C.
July 18th 18-5* 80-71 73-87 10-742 - 4-829 199-684 4-6480 4-6499
July 20th 18-9 77-01 71-46 10-716 - 4903 199-909 4-6460 4-6485
July 29th 17-5 80-025 82-40 10-713 - 54329 198-966 4-6488 4-6494
July 30th 18'9 80-725 77'25 10-723 -5-0553 199-640 4-6471 4-6496
Mean 4'6493 legal quadrants.
* There was a slight uncertainty about this temperature.