207 
as determined by chronometers at sea. 
have not received polarity by the too near approach of any 
thing magnetical) on ship-board. It appears probable, like- 
wise, that the force of the balance springs is affected in the 
same way ; since it is well known that chronometers having 
gold balance springs, although more difficult to adjust, yet 
keep better rates at sea than the others. 
However this may be, these observations show the neces- 
sity of not trusting to the rates of chronometers ascertained 
during the time they are on shore ; and if the rates are ascer- 
tained on board, the chronometers should always be kept in 
the same place, and also in the same position with respect to 
the ship ; for I have but little doubt that, upon an accurate 
trial, a chronometer will be found to change its rate, more or 
less, according as these circumstances are attended to. If these 
precautions are not taken, land will appear to be considerably 
to the westward of its true position ; this is particularly ex- 
emplified in the observations of the Hon. Captain Phipps ; 
from which, nearly the whole line of coast on the west side 
of East Greenland has been placed nearly 1 ~ ° too much to 
the westward, by reason of the acceleration of his chrono- 
meters ; the same circumstance would have occurred with 
the chronometers in both of the ships Dorothea and Trent, 
in the late voyage, had not the longitude been otherwise de- 
termined. Itis therefore highly requisite that attention should 
be paid to a circumstance so much connected with the im- 
provement of geography as well as the safety of the seaman. 
