voyage up the river Amazon, by William Henry Edwards, Wallace and Bates estimated that by collecting and selling natural history specimens such as birds and insects they could meet their costs, with the prospect of good profits. They therefore engaged as their agent Samuel Stevens who would advertise and arrange sales to institutions and private collectors, for a commission of 20% on sales plus 5% on despatching freight and remittances of money. In 1848, Wallace and Bates left for Brazil aboard the Mischief. They intended to collect insects and other animal specimens in the Amazon Rainforest for their private collections, selling the duplicates to museums and collectors back in Britain to fund the trip. Wallace hoped to gather evidence of the transmutation of species. Bates and he spent most of their first year collecting near Belém, then explored inland separately, occasionally meeting to discuss their findings. In 1849, they were briefly joined by another young explorer, the botanist Richard Spruce, along with Wallace's younger brother Herbert. Herbert soon left (dying two years later from yellow fever), but Spruce, like Bates, would spend over ten years collecting in South America. Wallace spent four years charting the Rio Negro, collecting specimens and making notes on the peoples and languages he encountered as well as the geography, flora, and fauna. On 12 July 1852, Wallace embarked for the UK on the brig Helen. After 25 days at sea, the ship's cargo caught fire, and the crew was forced to abandon ship. All the specimens Wallace had on the ship, mostly collected during the last, and most interesting, two years of his trip, were lost. He managed to save a few notes and pencil sketches, but little else. Wallace and the crew spent ten days in an open boat before being picked up by the brig Jordeson, which was sailing from Cuba to London. The Jordeson provisions were strained by the unexpected passengers, but after a difficult passage on short rations, the ship reached its destination on 1 October 1852. The lost collection had been insured for £200 by Stevens. After his return to Britain, Wallace spent 18 months in London living on the insurance payment, and selling a few specimens that had been shipped home. During this period, despite having lost almost all the notes from his South American expedition, he wrote six academic papers (including "On the Monkeys of the Amazon") and