Lunar observations.] 
APPENDIX. 
26 
Burg. He deduces from thence the longitude of Sydney Cove to be 
151° 12' 45" ; and from forty-four sets of lunar distances by lieutenant 
Flinders, it would be 151 0 11' 49" east. 
At Port Louis in the Isle Mauritius, the Abbe de la Caille 
observed an eclipse of the sun, the transit of mercury over the sun's 
disk, and various occultations of Jupiter's satellites ; M. dApres also 
observed several occultations ; and this place should therefore be 
well determined. Its longitude in the Requisite Tables is 57 0 20/ 15" 
east ; and from twenty-seven sets of distances taken whilst a prisoner 
there, I made it, when corrected for the errors of the tables, 
57° 2 9' 57" east. 
In appreciating the degrees of accuracy to which a small or 
larger number of lunar distances may be expected to give the longi- 
tude, I suppose the observer to be moderately well practised, hia 
sextant or circle, and time keeper to be good, and his calculations to 
be carefully made ; and it is also supposed, that the distances in the 
nautical almanack are perfectly correct. As, however, there may 
still be some errors, notwithstanding the science and the labour em- 
ployed to obviate them, it cannot be too much recommended to sea 
officers to preserve all the data of their observations ; more especially 
of such as may be used in fixing the longitudes of places but little, 
or imperfectly known. The observations may then be recalculated, 
if requisite ; the corrections found to be necessary may be applied ; 
and the observer may have the satisfaction of forwarding the pro- 
gress of geography and navigation, after having contributed to the 
safety of the ship, and benefit of the particular service in which he 
may happen to have been engaged. 
vol. 1. 
3O 
