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.
The 27-year-old FitzRoy had hopes of commanding a second expedition to continue the South American survey, but when he heard that the Lords of the Admiralty no longer supported this, he grew concerned about how to return the Fuegians. He made an agreement with the owner of a small merchant-vessel to take himself and five others back to South America, but a kind uncle heard of this and contacted the Admiralty. Soon afterwards, FitzRoy heard that he was to be appointed commander of HMS Chanticleer to go to Tierra del Fuego, but due to her poor condition, Beagle was substituted. On 27 June 1831, FitzRoy was commissioned as commander of the voyage, and Lieutenants John Clements Wickham and Bartholomew James Sulivan were both appointed.
Captain Francis Beaufort, the Hydrographer of the Admiralty, was invited to decide on the use that could be made of the voyage to continue the survey, and he discussed with FitzRoy plans for a voyage of several years, including a continuation of the trip around the world to establish median distances. Beagle was commissioned on 4 July 1831, under the command of Captain FitzRoy, who promptly spared no expense in having Beagle extensively refitted. Beagle was immediately taken into dock for extensive rebuilding and refitting. As she required a new deck, FitzRoy had the upper-deck raised considerably, by 8 inches (200 mm) aft and 12 inches (300 mm) forward. The Cherokee-class brig-sloops had the reputation of being "coffin brigs", which handled badly and were prone to sinking. By helping the decks to drain more quickly with less water collecting in the gunnels, the raised deck gave Beagle better handling and made her less liable to become top-heavy and capsize. Additional sheathing to the hull added about seven tons to her burthen and perhaps fifteen to her displacement.
The ship was one of the first to test the lightning conductor invented by William Snow Harris. FitzRoy obtained five examples of the Sympiesometer, a kind of mercury-free barometer patented by Alexander Adie and favoured by FitzRoy as giving the accurate readings required by the Admiralty.
In addition to its officers and crew, Beagle carried several supernumeraries, passengers without an official position. FitzRoy employed a mathematical instrument maker to maintain his 22 marine chronometers kept in his cabin, as well as engaging the artist/draughtsman Augustus Earle to go in a private capacity. The three Fuegians taken on the previous voyage were going to be returned to Tierra del Fuego on Beagle together with the missionary Richard Matthews.
Naturalist and geologist
For Beaufort and the leading Cambridge "gentlemen of science", the opportunity for a naturalist to join the expedition fitted with their drive to revitalise British government policy on science. This elite disdained research done for money and felt that natural philosophy was for gentlemen, not tradesmen. The officer class of the Army and Navy provided a way to ascend this hierarchy; the ship's surgeon often collected specimens on voyages, and Robert McCormick had secured the position on Beagle after taking part in earlier expeditions and studying natural history. A sizeable collection had considerable social value, attracting wide public interest, and McCormick aspired to fame as an exploring naturalist. Collections made by the ship's surgeon and other officers were government property, though the Admiralty was not consistent on this, and went to important London establishments, usually the British Museum. The Admiralty instructions for the first voyage had required officers "to use their best diligence in increasing the Collections in each ship: the whole of which must be understood to belong to the Public", but on the second voyage this requirement was omitted, and the officers were free to keep all the specimens for themselves.
FitzRoy's journal written during the first voyage noted that, while investigating magnetic rocks near the Bárbara Channel, he regretted "that no person in the vessel was skilled in mineralogy, or at all acquainted with geology", to make use of the opportunity of "ascertaining the nature of the rocks and earths" of the areas surveyed. FitzRoy decided that on any similar future expedition, he would "endeavour to carry out a person qualified to examine the land; while the officers, and myself, would attend to hydrography." This indicated a need for a naturalist qualified to examine geology, who would spend considerable periods onshore away from the ship. McCormick lacked expertise in geology and had to attend to his duties on the ship.
FitzRoy knew that commanding a ship could involve stress and loneliness. He was aware of his uncle Viscount Castlereagh's suicide due to stress from overwork, as well as Captain Stokes's suicide. This was to be the first time that FitzRoy would be fully in charge of a ship with no commanding officer or second captain to consult. It has been suggested that he felt the need for a gentleman companion who shared his scientific interests and could dine with him as an equal, although there is no direct evidence to support this. Professor John Stevens Henslow described the position "more as a companion than a mere collector", but this was an assurance that FitzRoy would treat his guest as a gentleman naturalist. Several other ships at this period carried unpaid civilians as naturalists.
Early in August, FitzRoy discussed this position with Beaufort, who had a scientific network of friends at the University of Cambridge. At Beaufort's request, mathematics lecturer George Peacock wrote from London to Henslow about this "rare opportunity for a naturalist", saying that an "offer has been made to me to recommend a proper person to go out as a naturalist with this expedition", and suggesting the Reverend Leonard Jenyns. Though Jenyns nearly accepted and even packed his clothes, he had concerns about his obligations as vicar of Swaffham Bulbeck and about his health, therefore Jenyns declined the offer. Henslow briefly thought of going, but his wife "looked so miserable" that he quickly dropped the idea. Both recommended bringing the 22-year-old Charles Darwin, who was on a geology field trip with Adam Sedgwick. He had just completed the ordinary Bachelor of Arts degree which was a prerequisite for his intended career as a parson.
Offer of place to Darwin
Darwin fitted well the expectations of a gentleman natural philosopher and was well trained as a naturalist. When he had studied geology in his second year at Edinburgh, he had found it dull, but from Easter to August 1831, he learned a great deal with Sedgwick and developed a strong interest during their geological field trip. On 24 August Henslow wrote to Darwin:
...that I consider you to be the best qualified person I know of who is likely to undertake such a situation—I state this not on the supposition of yr. being a finished Naturalist, but as amply qualified for collecting, observing, & noting any thing worthy to be noted in Natural History. Peacock has the appointment at his disposal & if he can not find a man willing to take the office, the opportunity will probably be lost—Capt. F. wants a man (I understand) more as a companion than a mere collector & would not take any one however good a Naturalist who was not recommended to him likewise as a gentleman. ... The Voyage is to last 2 yrs. & if you take plenty of Books with you, any thing you please may be done ... there never was a finer chance for a man of zeal & spirit... Don't put on any modest doubts or fears about your disqualifications for I assure you I think you are the very man they are in search of.