APPENDIX. 
[South Coast. 
circumstances are favourable, then lunar observations taken in 1814 
and afterwards, may be entitled to confidence within the following 
limits : 
From one set of distances, consisting of six independent sights, 
the error in longitude may be 30' on either side ; but will probably 
not exceed 12'. 
From six sets on one side of the moon, each set consisting as 
above, the error maybe 20' ; but not probably more than 8'. 
Twelve sets of distances, of which six on each side of the moon, 
are not likely to err more than 10' from the truth; and may be 
expected to come within 5'. 
The error in sixty sets, taken during three or four lunations, 
and one half on each side of the moon, will not, I think, be wrong 
more than 5' ; and will most probably give the longitude exact to 
1' or 2'. This degree of accuracy is far beyond what the hopes of 
the first proposers of the lunar method ever extended, and even 
beyond what astronomers accustomed only to fixed observatories 
will be disposed to credit at this time ; but in thinking it probable that 
sixty sets of lunar distances will come within 1' or 2' of the truth, 
when compared with correct tables, I conceive myself borne out by 
the following facts. 
In Port Lincoln, I observed an eclipse of the sun with a re- 
fracting telescope of forty-six inches focus, and a power of about 
two hundred. It was recalculated by Mr. Crosley from Delambre's 
and Burckhardt's tables, the one made four and the other ten years 
afterwards. The longitude deduced from the beginning differed 
only i's 1 " »5 ^ rom tnat at tne end ' and t ' le mean of botn onl y a 7" 
from thirty sets of lunar distances corrected for the errors of the 
tables. 
The Spanish admiral D'Espinosa observed emersions of the 
first and second satellites of Jupiter in 1793, at Port Jackson, and 
also an eclipse of the sun which he recalculated by the tables cf 
