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.

[34] When Darwin returned home from the field trip late on 29 August and opened the letters,[35] his father objected strongly to the voyage so, the next day, he wrote declining the offer[36] and left to go shooting at the estate of his uncle Josiah Wedgwood II.

[41] The Tory FitzRoy had been cautious at the prospect of companionship with this unknown young gentleman of Whig background, and later admitted that his letter to Wood was "to throw cold water on the scheme" in "a sudden horror of the chances of having somebody he should not like on board".

Before they left England, FitzRoy gave Darwin a copy of the first volume of Lyell's Principles of Geology which explained features as the outcome of a gradual process taking place over extremely long periods of time.

Darwin's notebooks show complete professionalism that he had probably learnt at the University of Edinburgh when making natural history notes while exploring the shores of the Firth of Forth with his brother Erasmus in 1826 and studying marine invertebrates with Robert Edmund Grant for a few months in 1827.

[85] Later, FitzRoy had to remain silent when Captain Paget of the frigate HMS Samarang (another British vessel surveying the region which often crossed paths with the Beagle) visited them and recounted "facts about slavery so revolting" that undermined his claim.

[110] At Bahía Blanca, in the southern part of present Buenos Aires Province, Darwin rode inland into Patagonia with gauchos: he saw them use bolas to bring down "ostriches" (rheas) and ate roast armadillo.

[113] With assistance (possibly from the young sailor Syms Covington acting as his servant[114][115]), Darwin collected numerous fossils over several days,[116] amusing others with "the cargoes of apparent rubbish which he frequently brought on board".

[127] They reached Tierra del Fuego on 18 December 1832, and Darwin was taken by surprise at what he perceived as the crude savagery of the Yaghan natives, in stark contrast to the "civilised" behaviour of the three Fuegians they were returning as missionaries (who had been given the names York Minster, Fuegia Basket and Jemmy Button).

[130] After three days at Bahía Blanca, he grew tired of waiting for Beagle, and on 21 August, revisited Punta Alta where he reviewed the geology of the site in light of his new knowledge, wondering if the bones were older than the seashells.

[140][141] His notes included a page showing his realisation that the cliff banks of the rivers exposed two strata formed in an estuary interrupted by an undersea stratum, indicating that the land had risen and fallen.

[130] On 9 January 1834, 110 miles (180 km) further south, they reached Port St Julian and exploring the local geology in cliffs near the harbour Darwin found fossils of pieces of spine and a hind leg of "some large animal, I fancy a Mastodon".

This raised awkward questions; it jarred with Charles Lyell's sheltered views, expressed in volume 2 of his Principles of Geology, that human races "showed only a slight deviation from a common standard", and that acceptance of transmutation meant renouncing man's "belief in the high genealogy of his species".

The giant Mastodons and Megatheriums were extinct, but he had found no geological signs of a "diluvial debacle" or of the changed circumstances that, in Lyell's view, led to species no longer being adapted to the position they were created to fit.

Darwin noted the horrors of death and destruction, and FitzRoy carefully established that mussel beds were now above high tide, giving clear evidence of the ground rising some 9 ft (2.7 m), which he confirmed a month later.

"[163] After going on to Mendoza, they were returning by a different pass when they found a petrified forest of fossilised trees, crystallised in a sandstone escarpment showing him that they had been on a Pacific beach when the land sank, burying them in the sand which had been compressed into rock, then had gradually been raised with the continent to stand at 7,000 ft (2,100 m) in the mountains.

[164][165] On 14 June, when about to leave Valparaiso,[166] FitzRoy had received news of the shipwreck of HMS Challenger captained by his friend Michael Seymour[167] (Darwin had arranged two boxes for this packet ship early in the year[81][168]).

FitzRoy rode about 64 kilometres (40 mi) on horseback with a guide to reach Seymour's camp at the Lebu River, then returned to further disputes before Blonde set out and rescued the survivors of the shipwreck on 5 July.

Arriving at Tahiti on 15 November, he soon found interest in luxuriant vegetation and the pleasant intelligent natives who showed the benefits of Christianity, refuting allegations he had read about tyrannical missionaries overturning indigenous cultures.

[185][186] Beagle visited Hobart, Tasmania, where Darwin was impressed by the agreeable high society of the settlers but noted that the island's "Aboriginal blacks are all removed & kept (in reality as prisoners) in a Promontory, the neck of which is guarded.

He provided boiled rice for an aboriginal "Corrobery" dancing party performed by the men of two tribes to the great pleasure of the women and children, a "most rude barbarous scene" in which everyone appeared in high spirits, "all moving in hideous harmony" and "perfectly at their ease".

[199] Their discussion is not recorded, but a few months earlier, on 20 February 1836, Herschel had written to Lyell praising his Principles of Geology as a work which would bring "a complete revolution in [its] subject, by altering entirely the point of view in which it must thenceforward be contemplated."

[209] Beagle reached Ascension Island on 19 July 1836,[210] and Darwin was delighted to receive letters from his sisters with news that Sedgwick had written to Dr. Butler: "He is doing admirably in S. America, & has already sent home a Collection above all praise.— It was the best thing in the world for him that he went out on the Voyage of Discovery— There was some risk of his turning out an idle man: but his character will now be fixed, & if God spare his life, he will have a great name among the Naturalists of Europe.

[213]) On 23 July, they set off again longing to reach home, but FitzRoy, who wanted to ensure the accuracy of his longitude measurements, took the ship across the Atlantic back to Bahia in Brazil to take check readings.

"[214] The return trip was delayed for a further 11 days when weather forced Beagle to shelter further up the coast at Pernambuco, where Darwin examined rocks for signs of elevation, noted "Mangroves like rank grass", and investigated marine invertebrates at various depths on the sandbar.

[215] On the stormy night of 2 October 1836, immediately after arriving in Falmouth,[215] Darwin set off on the Royal Mail coach from Fish Strand Hill (a plaque now marks the site[216]) for the two-day journey to his family home, The Mount House in Shrewsbury, Shropshire.

As he wrote to FitzRoy, the countryside they passed was "beautiful & cheerful", and though the "stupid people on the coach did not seem to think the fields one bit greener than usual", he now knew "that the wide world does not contain so happy a prospect as the rich cultivated land of England".

As a scientific celebrity with a reputation established by his fossils and the wide distribution of Extracts from Letters to Henslow on South American natural history and geology, Darwin toured London's social institutions.

[229] Darwin's find from Punta Alta, a large surface about 3 by 2 ft (0.91 by 0.61 m) doubled over with toe bones still inside the folded armour,[116] was identified as a slightly smaller Glyptodont named Hoplophorus by Peter Wilhelm Lund in the same year.

[234] The pieces of spine and a hind leg from Port S. Julian, which Darwin had thought came from "some large animal, I fancy a Mastodon", gave Owen difficulties, as the creature which he named Macrauchenia appeared to be a "gigantic and most extraordinary pachyderm", allied to the Palaeotherium, but with affinities to the llama and the camel.