at the Island of Balta, and at Woolwich Common. 441 
island. My reflections in reference to this point bear date ‘ Au- 
gust Sth, 1817,” in my journal, and were read to Dr. Wollaston 
and Captain Kater on the 4th of December, when they came to 
Woolwich to examine the clock. 
On the return of the clock to Woolwich its rate was again tried 
by Mr. Evans at his observatory, and found to be nearly the same 
as it had been in the preceding March and April. After this I 
set it up for experiment, at my own residence, as before described; 
and had scarcely got it in motion when Colonel Mudge explained 
to me the intenticn of the smaller nut, which his severe indispo- 
sition had prevented him from doing when at Leith. This ex- 
planation, while it accounted satisfactorily for the apparently 
small acceleration at Balta, tended in no degree to diminish. the 
rational confidence which might be placed in the invariability of 
the clock’s motion while it was there; but simply made me the 
more solicitous to obtain the correct result at Woolwich, that the 
aggregate acceleration due to the change of latitude might be- 
come known: after which I was, of course, desirous to appreciate 
the real effect of the supplementary nut upon the pendulum. The 
aggregate acceleration, therefore, having beeu determined, as al- 
ready described in this paper, I stopped the clock and inverted 
the nut, so as to make ¢ d’ upwards and c d below it, leaving the 
nut ab as before, and bringing up the smaller nut so as to be in 
contact with it. This I did because it was evident that such a 
process would produce a greater effect in the rate than would 
have been occasioned by depressing the smaller nut four or five 
threads of the screw. The inversion, however, considering that . 
this smaller nut weighed less than three quarters of an ounce, 
could not be expected to produce more than a slightly percepti- 
ble effect ; and thus it was found in fact; for before the supple- 
mentary nut was inverted the rate at Woolwich common was 
—19°72 (as before stated), while after inversion the rate ap- 
peared to be about —I9°S. 
I next took off the smaller nut entirely, and found the rate of 
the clock, on a mean of seven days, to be +82, differing very . 
little from what it had been found by Mr. Evans. 
Early in 1818 the clock was removed from my house to the 
new Observatory at the Royal Military Academy, in north lati- 
tude 51°28’ 2975. During the months of January, February, 
and March that year, by observations on stars south of the zenith, 
I ascertained the rate of the clock with the smaller nut on and 
off alternately, twice in succession; allowing several days to each 
trial. The first comparison gave 20/"4, the second gave 202, 
for the variation of the rate occasioned by this change in the cir- 
cumstances of the pendulum. 
Bearing in mind that in the intervals between the experiments 
here 
