ACCELERATION OF THE PENDULUM. 
clxv 
The stations of the present voyage were, 
In London, Latitude as before, 
At Melville Island, in the Polar Sea, Lat. 74° 47' 14".36 N, 
And again, in London, on the return of the Expedition. 
The observations of the second voyage are deserving of principal consi- 
deration, for the following reasons : 
1st. The arc of intercepted latitude was greater than between any two of 
the stations of 1818 ; the possible errors of observation have consequently 
had a less influence on the accuracy of the deductions. 
2dly. The employment of two clocks afforded a means of procuring double 
and corresponding results ; indeed, as it happened fortunately that each 
pendulum would fit into either clock, four corresponding results were 
obtained for the acceleration between London and Melville Island. 
3dly. The number of vibrations made by the clocks in London was ascer- 
tained by two distinct series of experiments, one before the departure, and 
a second after the return of the Expedition ; the very near agreement of the 
results on these occasions proving that neither of the clocks, nor any part of 
their apparatus, had sustained an injury during the voyage, affecting their 
rate of going ; as well as affording a satisfactory inference of the confidence 
which is due to the mode of experiment ; the number of vibrations in 
24 hours in London was as follows : 
. _ (k January, 1819 
Clock 1 < _ , _ 
('December, 1820 
Clock 2 
March, 1819 
December, 1820 
86392.5673 
86392.3353 
86392.4513 
86496.997 
86496.9741 
86496.9855 
Vibrations in a 
mean solar day. 
4thly. From the time which was allowed for the experiments at Melville 
Island being fully sufficient for their completion, the rate of each clock being 
determined by a mean of 85 intervals of 24 hours each. 
And lastly, From the correspondence in the results obtained by the two 
clocks ; the daily acceleration of the one, on a mean of the experiments 
with both pendulums, being 74.8151 vibrations, and by the other, 74.6528 
vibrations. The mean of the two, therefore, 74.734, is considered as the true 
