which, with all others not before in common use, are explained on the
General Chart, Plate I.

To have laid down no more than the lands and dangers seen in the
Investigator and other vessels under my command, would have left several
open spaces, and obliged the seaman to have recourse to other charts
where the difference of positions might have perplexed; the discoveries
and examinations of former navigators which come within the sphere of
each sheet, are therefore incorporated with, or added to mine, but so
marked as to be distinctly known. In making the combination, alterations
in their longitudes were frequently necessary to agreement; and that they
might be made with every regard to accuracy, the charts of the former
discoveries were compared with the astronomical observations, narratives,
or manuscript journals, when such could be had, and the alterations
introduced where there seemed to be the best authority. This has been
done with the charts of the east coast of New South Wales, published by
Mr. Dalrymple from the manuscripts, as it should appear, of captain Cook;
and since it may be thought presumptuous in me to have made alterations
in any work of so great a master, this case is selected for a more
particular explanation.

Time keepers were in their infancy in 1768, when captain Cook sailed upon
his first voyage, and he was not then furnished with them; his longitude
was therefore regulated only by occasional observations of lunar
distances and some few of Jupiter's satellites, which even in the present
improved state of instruments and tables, require to be connected by time
keepers before satisfactory conclusions can be drawn. Errors of greater
or less magnitude were thence unavoidable; at Cape Gloucester, where I
quitted the East Coast, my longitude was 20½' greater than captain Cook's
chart--at Cape York where the survey was again resumed, it was 58½; and