for scientific geography was the improvement that had
taken place in accurate chronometry. To find the latitude of a
place is not so difficult--the length of the day at different times
of the year will by itself be almost enough to determine this, as
we have seen in the very earliest history of Greek geography--but
to determine the longitude was a much more difficult task, which
in the earlier stages could only be formed by guesswork and dead
reckonings.

But when clocks had been brought to such a pitch of accuracy that
they would not lose but a few seconds or minutes during the whole
voyage, they could be used to determine the difference of local
time between any spot on the earth's surface and that of the port
from which the ship sailed, or from some fixed place where the clock
could be timed. The English government, seeing the importance of
this, proposed the very large reward of L10,000 for the invention
of a chronometer which would not lose more than a stated number of
minutes during a year. This prize was won by John Harrison, and
from this time onward a sea-captain with a minimum of astronomical
knowledge was enabled to know his longitude within a few minutes.
Hadley's sextant and Harrison's chronometer were the necessary
implements to enable James Cook to do his work, which was thus,
both in aim and method, in every way English.

James Cook was a practical sailor, who had shown considerable
intelligence in sounding the St. Lawrence on Wolfe's expedition,
and had afterwards been appointed marine surveyor of Newfoundland.
When the Royal Society determined to send out an expedition to
observe the transit of Venus, according to Halley's prediction,
they were deterred from entrusting the expedition to a scientific
man by the example of Halley himself, who had failed to obtain
obedience from sailors on being entrusted with the command. Dalrymple,
the chief hydrographer of the Admiralty, who had chief claims to
the command, was also somewhat of a faddist, and Cook was selected
almost as a _dernier ressort_. The choice proved an excellent one.
He selected a coasting coaler named the _Endeavour_, of 360 tons,
because her breadth of beam would enable her to carry more stores
and to run near coasts. Just before they started Captain Wallis
returned from a voyage round the world upon which he had discovered
or re-discovered Tahiti, and he recommended this as a suitable
place for observing the transit.

Cook duly arrived