The second survey expedition of HMS Beagle took place from 27 December 1831 to 2 October 1836. Robert FitzRoy, the newest commander of Beagle, had thought of the advantages of having someone onboard who could investigate geology, and sought a naturalist to accompany them as a supernumerary. At the age of 22, the graduate Charles Darwin hoped to see the tropics before becoming a parson, and accepted the opportunity. He was greatly influenced by reading Charles Lyell's Principles of Geology during the voyage. By the end of the expedition, Darwin had made his name as a geologist, and fossil collector, and the publication of his journal (later known as The Voyage of the Beagle) gave him wide renown as a writer. Beagle sailed across the Atlantic Ocean, and then carried out detailed hydrographic surveys around the coasts of southern South America, returning via Tahiti and Australia, after having circumnavigated the Earth. The initial offer to Darwin told him the voyage would last two years; it lasted almost five. Darwin spent most of this time exploring on land: three years and three months on land, 18 months at sea. Early in the voyage, Darwin decided that he could write a geology book, and he showed a gift for theorising. At Punta Alta in Argentina, he made a major find of gigantic fossils of extinct mammals, then known from very few specimens. He collected and made detailed observations of plants and animals. His findings undermined his belief in the doctrine that species are fixed, and provided the basis for ideas which came to him when back in England, leading to his theory of evolution by natural selection.
Aims of the expedition
When the Napoleonic Wars ended in 1815, the Pax Britannica saw seafaring nations competing in colonisation and rapid industrialisation. The logistics of supply and growing commerce needed reliable information about sea routes, but existing nautical charts were incomplete and inaccurate. Spanish American wars of independence ended Spain's monopoly over trade, and the UK's 1825 commercial treaty with Argentina recognised its independence, increasing the naval and commercial significance of the east coast of South America. The Admiralty instructed Commander King to make an accurate hydrographic survey of "the Southern Coasts of the Peninsula of South America, from the southern entrance of the River Plata, round to Chilóe; and of Tierra del Fuego". As Darwin wrote of his voyage, "The object of the expedition was to complete the survey of Patagonia and Tierra del Fuego, commenced under Captain King in 1826 to 1830—to survey the shores of Chile, Peru, and of some islands in the Pacific—and to carry a chain of chronometrical measurements round the World." The expeditions also had diplomatic objectives, visiting disputed territories. An Admiralty memorandum set out the detailed instructions. The first requirement was to resolve disagreements in the earlier surveys about the longitude of Rio de Janeiro, which was essential as the base point for meridian distances. The accurate marine chronometers needed to determine longitude, had only become affordable since 1800; Beagle carried 22 chronometers to allow corrections. The ship was to stop at specified points for a four-day rating of the chronometers and to check them by astronomical observations: it was essential to take observations at Porto Praya and Fernando de Noronha to calibrate against the previous surveys of William Fitzwilliam Owen and Henry Foster. It was important to survey the extent of the Abrolhos Archipelago reefs, shown incorrectly in Albin Roussin's survey, then proceed to Rio de Janeiro to decide the exact longitude of Villegagnon Island off the Brazilian coast. The real work of the survey was then to commence south of the Río de la Plata, with return trips to Montevideo for supplies; details were given of priorities, including surveying Tierra del Fuego and approaches to harbours on the Falkland Islands. The west coast was then to be surveyed as far north as time and resources permitted. The commander would then determine his own route west: season permitting, he could survey the Galápagos Islands. Then, Beagle was to proceed to Point Venus, Tahiti, and on to Port Jackson, Australia, which were known points to verify the chronometers. No time was to be wasted on elaborate drawings; charts and plans should have notes and simple views of the land as seen from the sea showing measured heights of hills. Continued records of tides and meteorological conditions were also required. An additional suggestion was for a geological survey of a circular coral atoll in the Pacific Ocean including its profile and of tidal flows, to investigate the formation of such coral reefs.
Context and preparations The previous survey expedition to South America involved HMS Adventure and HMS Beagle under the overall command of the Australian Commander Phillip Parker King. During the survey, Beagle's captain, Pringle Stokes, committed suicide and command of the ship was given to the young aristocrat Robert FitzRoy, a nephew of George FitzRoy, 4th Duke of Grafton. When a ship's boat was taken by the natives of Tierra del Fuego, FitzRoy tried taking some of them hostage, and after this failed he got occupants of a canoe to put another on the ship in exchange for buttons. He brought four of them back to England to be given a Christian education, with the idea that they could eventually become missionaries. One died of smallpox. After Beagle's return to Devonport dockyard on 14 October 1830, Captain King retired.
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