Bonpland became friendly with Jussieu and Lamarck after graduating from university. He met Humboldt by chance, staying at the same hotel in Paris; they travelled together for five years undertaking wide-ranging and often pioneering scientific research in Central and South America, and visited Jefferson in Washington. Humboldt credited Bonpland in all 23 volumes of his published research, rather than just the two that he collaborated on. Bonpland translated a Spanish work for Cuvier (who later thanked him for the continuing supply of South American specimens), and met Banks.
Cook was an established explorer-cartographer — some of his astonishing charts were used until the mid-20thC — and had presented an astronomical paper to the Royal Society, before he led three famous voyages of scientific exploration. Banks (paying his own way) and Solander were naturalists on Cook’s first voyage, the Forsters taking their place on the second after Cook baulked at Banks’s demands; unfortunately, the elder Forster and Cook quickly became disenchanted with one another. Maskelyne supported and corresponded with Cook. Boswell met him at Pringle’s, and “felt a strong inclination to go with him on his next voyage.”
Humboldt, a small man and intellectual giant, was uncommonly well-connected. Werner taught him geology. Gay-Lussac savaged some of his work, but they became friends and ascended Vesuvius in eruption. He named the brazil-nut tree after Berthollet, travelled in the Low Countries and England with Forster, explored Latin America with Bonpland, and met Jefferson. Felix Mendelssohn, a family friend, dedicated a cantata to him. He wrote to Arago, starting 40 years’ friendship; Faraday was another correspondent. He knew Heine and Darwin, met Meyerbeer frequently, contributed to Schiller’s periodical, and taught Agassiz geology.
Despite d’Orbigny’s obsolete ideas (including that there had been 28 creations of life, and 27 total extinctions), much of his detailed work has had continued relevance. Audubon was a childhood friend in France (d’Orbigny’s father gave him drawing lessons). Cuvier and Geoffroy taught him, and were responsible for the seven-year South American expedition he undertook (Cuvier died while he was away). Humboldt, met in Paris (and whose colleague Bonpland was a family friend of the d’Orbigny’s), correctly asserted that the funds for the expedition wouldn’t be enough. Darwin corresponded though never met him, and thought his work second only to Humboldt’s.
Bates, met in a library, introduced him to insect-collecting; they separated two years into their Amazon expedition. Wallace corresponded with Darwin from the East Indies, sending him animal specimens; a paper he sent a startled Darwin from Sarawak, setting out his case for natural selection, was passed on to Lyell, who with Hooker worked out a form of tandem publication to clarify Darwin’s priority (Darwin later lobbied for a government pension for Wallace). Wallace was in touch with a wide network of scientists (Galton a particular friend), discussed spiritualism with Tennyson, and was invited by Mill to argue for land-tenure reform.
A notable scientific polymath, Galton was Darwin’s cousin; they corresponded enthusiastically, intrigued by each other’s researches — Galton’s invention of the field of statistical analysis can be said to have had its roots in Darwin’s work. De Candolle was also an influential correspondent, forcing him to reformulate the nature/nurture debate; other correspondents included Wallace (a friend), Stokes, Rayleigh and Maxwell. Herschel taught him the use of an instrument of his own devising; the young Cattell worked alongside him. Hooker, Spencer and Bentham were all friends, while the statistically-minded Nightingale mooted a professorship with him.