Adam Richter is a historian of science who specializes in the relationship between science and religion; he has published on John Wallis (1616-1703). Here, he writes about the correspondence between Wallis and Sloane.
When Hans Sloane became secretary of the Royal Society in 1693, John Wallis was about to enter the last decade of his life. Wallis is best known as a mathematician, but he was also—besides a linguist, a theologian, a logician, and many other things—an accomplished natural philosopher. Born in 1616, Wallis started down the path toward an ecclesiastical career, until 1649 when he was installed as Savilian Professor of Geometry at Oxford by Oliver Cromwell’s regime. By then he also had connections with the London-based group of natural philosophers that would evolve into the Royal Society, of which he was a founding member. After the Society’s official founding in 1660, he remained one the most active Fellows, sending in observations and experimental results from Oxford. When Wallis died in 1703, Sloane’s star was still rising, as he would go on to become president of both the Royal College of Physicians in 1719 and the Royal Society in 1727. Thus, the correspondence between Wallis and Sloane in the 1690s and early 1700s, which almost exclusively consists of Royal Society business, represents a meeting of two generations of Fellows, a point of contact between the Society’s seventeenth- and eighteenth-century periods.
Wallis was highly active in the Society’s affairs, but since he was not based in London, he participated primarily through correspondence. Many letters from Wallis to Sloane have survived, but, sadly, we have only three letters from Sloane to Wallis. This is typical of Sloane’s correspondence, since he rarely kept drafts of the letters he sent. Copies of his outgoing letters are relatively scarce and are scattered among repositories throughout the United Kingdom and Europe. From the extant letters, it seems that the correspondence proceeded much like that between Wallis and other secretaries of the Royal Society since Henry Oldenburg, who was secretary from the Society’s founding until his death in 1677. As secretary, Sloane was responsible for passing along letters, keeping records of scientific developments, and sometimes arbitrating disputes between Fellows. Wallis sent letters to Sloane expecting them to be conveyed to other natural philosophers and mathematicians, or printed in the Philosophical Transactions which Sloane was in charge of publishing. For his part, Sloane would pass along requests from the Society for Wallis’s views on various matters, including, for instance, a case in 1698 when an unusual optical effect caused people to observe three different suns. Since Wallis was an experienced observer of meteorological and astronomical phenomena, the Society wanted him to determine whether this was, as Sloane put it, “any thing extraordinary or only a Common meteor.” Sloane also sent Wallis copies of the Philosophical Transactions, which Wallis eagerly anticipated as a means to keep up on the Society’s latest experiments and observations.
By this time, the elderly Wallis had come to adopt a rather fatherly attitude toward younger Fellows like Sloane. He sometimes praised Sloane for his work, but at other times he chided the secretary for falling behind on publishing the Philosophical Transactions. Wallis’s withering ‘parental’ disappointment is palpable in a letter of 29 November 1701: “The year now draws toward an End; and you are somewhat behind hand in your Transactions. I have seen none since that for August.” On other occasions, having sent Sloane material to be included in the journal, he chastised the secretary for mistakes that appeared on the printed version. On 10 October 1699, he thanked Sloane for sending the August issue of the Philosophical Transactions, which contained an excerpt of a letter to Wallis from Gottfried Leibniz. But Wallis was not impressed by what he received:
I am Sorry to find so many Gross Errata in that for August in the Latin Letter, which I was afraid of, and therefore desired the favour of you to have it rectifyed (after the first Correction) before it was wrought off at the Press. … I find it Generally Complained of that your printers are too negligent as to Correcting the press. which is to the Disadvantage of the Transactions; and I wish (& so do others) that more care may be had of it for the future. For it adds to the Reputation of the Transactions that they be well printed and Correctly.
Sloane’s replies to these letters have not survived, so we don’t know how he responded to Wallis’s disappointment. In any case, Wallis’s concern for the Society’s reputation seems sincere. For decades he had been concerned that England’s natural philosophers would be overshadowed by continental rivals, particularly if their achievements were not sufficiently publicized and celebrated. This is evident, for instance, when he writes to Sloane on 30 December 1701 proposing a project intended, presumably, for a younger member of the Royal Society. In his letter, Wallis makes a long digression describing various English contributions to the study of magnetism, beginning with the work of William Gilbert (1544-1603). He then adds:
And (in General) the Doctrine of Magnetism hath been more improved by our English Naturalists, than (for ought I know) by any other Nation. And, if some of our Gres-hamites would take the pains to give us a true History of these (and the like) improvements; it would be an acceptable service, for the Honour of the Nation, and of that Colledge in particular, and of the Royal Society.
Here we see Wallis, now 85 years old, offering up a project that he probably would have undertaken himself when he was younger. Sloane, evidently sharing Wallis’s concern about proper recognition of English achievement in magnetism, published this letter in the Philosophical Transactions.
The above examples may suggest that Sloane was a passive participant in the Royal Society’s activities, simply facilitating contact between scholars of Wallis’s stature. This was far from the case: Wallis trusted Sloane as a knowledgeable member of the scholarly community and he valued the secretary’s opinion highly in matters of natural philosophy. For instance, on 3 February 1699/1700 Wallis wrote to Sloane to set up a correspondence between him and the anatomist Edward Tyson (1651-1708). Wallis had developed a theory that the natural diet of animals corresponds to the anatomy of their digestive system: herbivores have a longer colon with a pouch at the upper end called a caecum, while carnivores have a shorter colon and lack the caecum. Humans have a short and seemingly useless caecum, which makes sense for a species that can tolerate meat but only in moderation, and only when it’s cooked before consumption. Wallis concludes that humans are essentially herbivores, as true carnivores don’t need to take any extra measures like cooking meat before eating it. As he asks Sloane to put him in touch with Tyson, Wallis also invites the secretary to evaluate the theory himself, noting that the letter is “unsealed that you may (if you please to give yourself the trouble) peruse it, & then convey it to [Tyson]”. Sloane’s reply, written three days later, is one of the few from his side of the correspondence that survives. He indeed gives Wallis his assessment of the theory, drawing on his own research on the subject to suggest that many different diets can be suitable for humans:
… I believe mankind can live on many sorts of vegetables & animals & their parts. I have gathered together an account of the severall kinds of food I meet with that are used in most parts of the world, some of which are very strange & yet sufficient to sustain nature. Our bodies are so contrived as to prepare & take out of all these substances what is beneficiall, turning of the useless excrements.
Sloane even suggests a book on the relationship between anatomy and diet that Wallis might not have consulted. In his appreciative reply of 9 February, Wallis notes that he hasn’t seen the book mentioned by Sloane, and although he pushes back a little to defend his take on the natural human diet, he concludes that the two of them agree on the major points.We can see from this exchange that Wallis treats his younger colleague not merely as a facilitator of scholarly communication, but rather as a peer in matters of natural philosophy.
It’s regrettable that we have so few letters from Sloane to Wallis—partly because the missing letters would add more information about certain tantalizing episodes mentioned by Wallis, such as the “prodigiously strong man, which we heard of last summer” about whom Wallis requests an update (13 June 1700). Fortunately, the many surviving letters from Wallis to Sloane paint a fairly complete picture. These letters run up 1 July 1703, around four months before Wallis’s death. Clearly, to have carried on their correspondence until that point, he must have regarded Sloane as a useful and reliable correspondent. He could count on Sloane as a knowledgeable intermediary, and sometimes an active participant, in natural philosophical affairs, and (despite the occasional rebuke) as someone with the practical and people skills to keep the wheels of the Royal Society turning. This would have been no small matter to someone like Wallis who had invested a great deal of time and effort into the Society since its earliest days.
 For a fuller biography of Wallis, see Jason Rampelt’s excellent new monograph (Jason M. Rampelt, Distinctions of Reason and Reasonable Distinctions: The Academic Life of John Wallis (1616-1703) [Leiden: Brill, 2019]).
 Nearly all of the surviving letters from Wallis to Sloane are contained in the British Library’s Sloane papers and the Royal Society’s early letter books. These sources contain few letters by Sloane himself. The Royal Society holds only one letter from Sloane to Wallis, and the British Library holds none.
 The Wallis correspondence is in the process of being published (Philip Beeley and Christoph Scriba, eds., The Correspondence of John Wallis[Oxford: Oxford University Press, 2003-]). As the editors have not yet reached the last years of Wallis’s life, the letters he exchanged with Sloane have not yet been included, and many exist only as manuscripts.
 In one such fascinating episode, Sloane tried to keep the peace between Gottfried Leibniz and certain English members of the Royal Society. After Wallis passed along Leibniz’s complaint of ill treatment by the Fellows, Sloane wrote to Wallis on 26 August 1699, asking him to communicate to Leibniz the Society’s “great respect for [Leibniz] and every thing [that] comes from him” (Hanover Niedersächsische Landesbibliothek LBr 974, f. 53r). Indeed, Sloane laments that earlier secretaries have let their correspondence with Leibniz lapse. There is no sense here of the coming priority dispute over calculus that would pit Leibniz and his supporters against Newton and the English scholarly community. On the calculus dispute, see Domenico Bertoloni Meli, Equivalence and Priority: Newton versus Leibniz (Oxford: Oxford University Press, 1993).
 Royal Society Early Letters B2, No. 49. Sloane’s letter seems to refer to the case described in “The Extract of a Letter from Mr. Petto, a Grave Divine, Concerning Some Parelii Seen at Sudbury in Suffolk, Decemb. 28th, 1698. Communicated by Dr. Beverley,” Phil. Trans. 21 (1699): 107-110.
 British Library MS Sloane 4025, f. 304.
 “A Letter of Dr. Wallis to Dr. Sloan [sic], Secretary to the Royal Society, Giving an Account of Some Late Passages between Him and Myn Heer Leibnitz, of Hannover,” Phil. Trans. 21 (1699): 273-274.
 Royal Society Letter Book Copy 12, p. 174.
 “A Second Letter of Dr Wallis to the Publisher, Relating to Mr Somner’s Treatise of Chartham News: And, Some Magnetick Affairs,” Phil. Trans.22 (1700-1701): 1037-1038.
 See Adam Richter, “On Food and Fossils: Natural Philosophy, Mathematics, and Biblical History in the Works of John Wallis,” The Seventeenth Century (2018): DOI: 10.1080/0268117X.2018.1541424.
 Royal Society Early Letters W2, No. 72.
 Wellcome Institute MS 7633/1.
 Royal Society Letter Book Original 12, p. 327.
 Further evidence of Wallis trusting Sloane to handle complex natural philosophical material is found in their correspondence about Wallis’s theory that England and France were once connected by a ‘land-bridge’ between Dover and Calais. See Philip Beeley, “Physical Arguments and Moral Inducements: John Wallis on Questions of Antiquarianism and Natural Philosophy,” Notes and Records: The Royal Society Journal of the History of Science 72 (2018): 413-430.
 British Library MS Sloane 4025, f. 318.