udy the manners and customs of the
natives with whom they came in contact, which neither the time at Cook's
disposal nor his training enabled him to undertake; and though the
Journal of the former has never yet been published, and cannot at the
present time be traced, many interesting remarks were extracted by Dr.
Hawkesworth from it and went far to make his account of the voyage
complete.

Mr. Green also demands special notice.

One great question of the day amongst seamen and geographers was the
discovering of some ready and sure method of ascertaining the longitude.
Half the value of the explorations made up to this time had been lost
from this want. The recognised means of finding longitude was by the
observation of lunars; that is, accurately measuring the angular distance
between the centres of the moon and of the sun, or of the moon and some
star.

The motion of the moon is so rapid that this angular distance changes
from second to second, and thereby, by previous astronomical calculation,
the time at Greenwich at which its distance from any body is a certain
number of degrees can be ascertained and recorded.

By well-known calculations the local time at any spot can be obtained,
and when this is ascertained, at the precise moment that the angular
distance of sun and moon is observed, the difference gives the longitude.

This seems simple enough, but there is a good deal of calculation to go
through before the result is reached, and neither the observation nor the
calculation is easy, especially with the astronomical tables of those
days, and there were very few sailors who were capable of, or patient
enough to make them, nor was the result, as a rule, very accurate. For
one thing, the motions of the moon, which are extremely complicated, were
not enough known to allow her calculated position in the heavens to be
very accurate, and a very small error in this position considerably
affects the time, and therefore the longitude.

Luckily for Cook, the Nautical Almanac had just been started, and
contained tables of the moon which had not previously been available, and
which much lightened the calculations.

The great invention of the chronometer, that is, a watch that can be
trusted to keep a steady rate for long periods, was at this time
completed by Harrison; but very few had been manufactured, and
astronomers and sailors were slow to believe in the efficacy of this
method of carrying time about with a ship