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 £10,000 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 there, and on the 3rd of June 1769 the main object of the expedition was fulfilled by a successful observation. But he then proceeded farther, and arrived soon at a land which he saw reason to identify with the Staaten Land of Tasman; but on coasting along this, Cook found that, so far from belonging to a great southern continent, it was composed of two islands, between which he sailed, giving his name to the strait separating them. Leaving New Zealand on the 31st of March 1770, on the 20th of the next month he came across another land to the westward, hitherto unknown to mariners. Entering an inlet, he explored the neighbourhood with the aid of Mr. Joseph Banks, the naturalist of the expedition. He found so many plants new to him, that the bay was termed Botany Bay.