VI. 
Observations on the Comparative Rates of Marine Chronometers. 
BY W. CRANCH BOND. 
TueE following series of observations was arranged, in conse- 
quence of an opinion being expressed by some navigators, that 
Chronometers, when removed from the shore to the ship, have 
an accelerated rate of going. This was attempted to be 
accounted for, on the supposition that the influence of iron would 
tend to produce such an effect. A paper on this subject by 
George Fisher Esq., read before the Royal Society, June 8, 1820, 
contained an account of some very extraordinary discrepancies ; 
and if such were common, they would render these instruments 
of little or no value, as a means of determining the longitude. 
But, upon examination of the rates of the several Chronometers 
as therein given, it appears, that the rates of these particular 
instruments were, even on shore, so unsteady as to make it 
probable that they were not in such a state as to be worthy of 
much confidence. For example, the Chronometer by Baird, 
from the 8th to the 12th of August, was losing 3”.4 daily when on 
board ; but on its removal to the observatory on shore, its rate of 
losing was observed to be 18”.2. Upon again removing it on board, 
it was found to be losing 6”.5 daily. Here we see a difference 
of 3’.1 in the ship-board rates. Another Chronometer, made 
