Mr. Fisher on the errors in longitude, &c. 197 
rates as determined in London previous to the ship’s sailing ; 
in consequence of which the land appeared considerably to 
the westward of its true position as determined by lunar ob- 
servation, and they were found to be still gaining daily, which 
appeared not only from each subsequent set of lunars, but also 
by comparing the longitude of different points of land deter- 
mined by the chronometers, with the longitude of the same 
points ascertained in the same way some time afterwards. 
For instance *, the longitude of a remarkable point of land 
on the north-west coast of Spitzbergen, called Cloven Cliff, 
was found by a mean of the observations taken with the 
chronometers on June 21, 1818, to be io° 35' 27"E ; but the 
longitude of the same point of land on July 3i,wasio°i5' 
37" E, making a difference of no less than about 20' of longi- 
tude in five weeks ; that is, estimating the longitude with 
the same rates and errors as determined in London before 
their departure ; from this, therefore, it appears, they had 
been gaining on their former rates, or had been increasing 
their gaining rates, and diminishing their losing ones. 
An opportunity soon afterwards occurred of observing the 
effect produced upon the chronometers by removing them on 
shore. On the 9th of August, the chronometers, nine in 
number, were landed on an island, where a temporary ob- 
servatory had been erected for the purpose, and the latitude 
of which had been accurately determined with a repeating 
circle made by Troughton, when it was found that the 
acceleration immediately ceased ; for the longitude of the 
place by chronometers, August 12, was 9°42 / 36 ,/ E, but on 
the 27th, it was io° i' o" E, making a difference of 18' 24/' of 
longitude in fifteen days, using the former rates. 
Since, therefore, the chronometers were getting easterly 
MDCCCXX. D d 
