an unpublished letter from henry oldenburg to johann heinrich rahn
an unpublished letter from henry oldenburg to johann heinrich rahn an unpublished letter from henry oldenburg to johann heinrich rahn
Downloaded from rsnr.royalsocietypublishing.org on December 6, 2012 Notes Rec. R. Soc. Lond. 58 (3), 249–266 (2004) doi 10.1098/rsnr.2004.0065 AN UNPUBLISHED LETTER FROM HENRY OLDENBURG TO JOHANN HEINRICH RAHN by NOEL MALCOLM All Souls College, Oxford OX1 4AL, UK SUMMARY The Swiss mathematician Johann Heinrich Rahn studied under John Pell in Zurich in the 1650s. Prompted by Pell (who worked on a revised version of Rahn’s treatise on algebra, which was published in London in 1668), Theodore Haak made contact with Rahn in 1671, and received a letter from him describing his recent work on optics. This letter was passed on to Henry Oldenburg, who, with the assistance of John Collins, composed a lengthy reply, surveying recent scientific and mathematical publications. Significantly, however, Oldenburg did not consult Pell, even though this correspondence arose in the first place from Pell’s friendship with Rahn; the reason for this omission was that Oldenburg and Collins hoped that Rahn could supply details of Pell’s mathematical methods that Pell himself was refusing to divulge. Oldenburg’s letter is published here for the first time. Keywords: early Fellows; Henry Oldenberg; Johann Heinrich Rahn; John Pell INTRODUCTION The correspondence of Henry Oldenburg (figure 1), conducted for the most part in his capacity as Secretary of The Royal Society, is a monument to his industry, curiosity, and tireless energy. In addition to dealing with an incoming tide of enquiries and requests, he was also active in making fresh contacts and seeking out information from new sources. There is evidence of this, in abundance, in the 13-volume modern edition of his correspondence. 1 One small piece of further evidence can now be added: a letter, omitted from that edition, that was sent by Oldenburg to the Swiss mathematician Johann Heinrich Rahn on 10 June 1671. This letter is preserved in a scribal copy in the Zentralbibliothek, Zurich, in a set of transcripts of letters to Rahn and his father. 2 It does not seem to have generated any subsequent exchange of letters between Rahn and Oldenburg; in that sense it may be regarded both as a rather solitary item and, in effect, as a failure. Nevertheless, the origins of this letter were far from solitary; understanding its full story involves tracing relations between Oldenburg and no fewer than three other Fellows of The Royal Society—Theodore Haak, John Pell and John Collins. And the letter also possesses, in addition to its intrinsic interest, some value as a case-study, illustrating the nature of some of the problems Oldenburg confronted when his role as a correspondent brought his personal obligations and his professional duties into conflict. 249 © 2004 The Royal Society
Downloaded from rsnr.royalsocietypublishing.org on December 6, 2012 250 Noel Malcolm JOHANN HEINRICH RAHN Johann Heinrich Rahn (1622–76) was a member of a prominent Zurich family: his father served as a city councillor for more than 50 years, and was Bürgermeister (Mayor) of Zurich from 1655 until his death in 1669. Rahn probably acquired his special interest in mathematics from his uncle Johann Georg Werdmüller, who was the engineer in charge of the city’s fortifications. He himself was appointed a ‘Schützenmeister’, which meant that he supervised shooting practice, and a ‘Zeugherr’, responsible for military supplies and artillery. 3 His mathematical interests were stimulated in 1654 by the arrival in Zurich of John Pell, the former Professor of Mathematics at Amsterdam and Breda (and future FRS), who served as Cromwell’s envoy to the Protestant cantons of Switzerland from May 1654 to June 1658. The first sign of his connection with Pell is a letter he sent, dated 4 November 1654, enclosing a short mathematical demonstration and thanking Pell for the gift of a copy of one of Pell’s publications, his compilation of texts refuting the Danish circle-squarer Longomontanus. 4 What further contacts they had over the next two years is not known, but at some time in early 1657 Rahn began to receive regular weekly tutorials from Pell. As John Aubrey would later write (summarizing what Pell had told him), ‘Rhonius [the latinized version of ‘Rahn’] was D r Pell’s scholar at Zurich, and came to him every friday night’; Pell himself would refer to Rahn as his ‘disciple’ and would retain ‘coppies of the most considerable papers that he wrought in my presence or that I gave him to transcribe’. 5 In early 1658 Rahn was appointed ‘Landvogt’ (provincial governor) of Kyburg, a district at the northern edge of the canton of Zurich; writing to Pell from there on 3 March 1658, he remarked that his heavy administrative workload prevented him from spending any time on mathematics, but said that he had the consolation of remembering ‘how many very delightful hours’ they had spent together. 6 Nevertheless, during the next year he somehow found time to compose the German-language textbook on algebra that would make him famous: Teutsche Algebra, oder algebraische Rechenkunst, zusamt ihrem Gebrauch (Zurich, 1659). This work was heavily indebted to Pell, and it was a debt that Rahn was happy to acknowledge (though, probably in deference to Pell’s own habitual modesty, without mentioning his name): Rahn explained in his preface that ‘in the solutions, and in the arithmetic too, I make use of a completely new method … which I first learned from an eminent and very learned person.’ This new method, he explained, consisted in ‘a triple margin’—Pell’s system of presenting the working-out of a problem in three columns. But that was not the only thing owed to Pell in this volume: Rahn also introduced the division sign (which Pell had invented), and in a section on squaring the circle he presented the theorem Pell had defended in his controversy with Longomontanus. 7 When Rahn’s book was published, Pell was back in London, leading a somewhat obscure existence without any public or academic position. He was no longer in touch with Rahn, but in November 1660 he did receive a copy of Rahn’s book from his friend Theodore Haak (the German-born scholar and translator, a man of wide scientific interests, who would be elected FRS in the following year). 8 Other copies evidently found their way to England, for in the early 1660s two separate translations of it were under-
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Notes Rec. R. Soc. Lond. 58 (3), 249–266 (2004) doi 10.1098/rsnr.2004.0065<br />
AN UNPUBLISHED LETTER FROM HENRY OLDENBURG TO JOHANN<br />
HEINRICH RAHN<br />
by<br />
NOEL MALCOLM<br />
All Souls College, Oxford OX1 4AL, UK<br />
SUMMARY<br />
The Swiss mathematici<strong>an</strong> Joh<strong>an</strong>n Heinrich Rahn studied under John Pell in Zurich in the<br />
1650s. Prompted by Pell (who worked on a revised version of Rahn’s treatise on algebra,<br />
which was published in London in 1668), Theodore Haak made contact with Rahn in 1671,<br />
<strong>an</strong>d received a <strong>letter</strong> <strong>from</strong> him describing his recent work on optics. This <strong>letter</strong> was passed<br />
on <strong>to</strong> Henry Oldenburg, who, with the assist<strong>an</strong>ce of John Collins, composed a lengthy reply,<br />
surveying recent scientific <strong>an</strong>d mathematical publications. Signific<strong>an</strong>tly, however,<br />
Oldenburg did not consult Pell, even though this correspondence arose in the first place<br />
<strong>from</strong> Pell’s friendship with Rahn; the reason for this omission was that Oldenburg <strong>an</strong>d<br />
Collins hoped that Rahn could supply details of Pell’s mathematical methods that Pell himself<br />
was refusing <strong>to</strong> divulge. Oldenburg’s <strong>letter</strong> is published here for the first time.<br />
Keywords: early Fellows; Henry Oldenberg; Joh<strong>an</strong>n Heinrich Rahn; John Pell<br />
INTRODUCTION<br />
The correspondence of Henry Oldenburg (figure 1), conducted for the most part in his<br />
capacity as Secretary of The Royal Society, is a monument <strong>to</strong> his industry, curiosity, <strong>an</strong>d<br />
tireless energy. In addition <strong>to</strong> dealing with <strong>an</strong> incoming tide of enquiries <strong>an</strong>d requests, he<br />
was also active in making fresh contacts <strong>an</strong>d seeking out information <strong>from</strong> new sources.<br />
There is evidence of this, in abund<strong>an</strong>ce, in the 13-volume modern edition of his correspondence.<br />
1 One small piece of further evidence c<strong>an</strong> now be added: a <strong>letter</strong>, omitted <strong>from</strong><br />
that edition, that was sent by Oldenburg <strong>to</strong> the Swiss mathematici<strong>an</strong> Joh<strong>an</strong>n Heinrich<br />
Rahn on 10 June 1671. This <strong>letter</strong> is preserved in a scribal copy in the Zentralbibliothek,<br />
Zurich, in a set of tr<strong>an</strong>scripts of <strong>letter</strong>s <strong>to</strong> Rahn <strong>an</strong>d his father. 2 It does not seem <strong>to</strong> have<br />
generated <strong>an</strong>y subsequent exch<strong>an</strong>ge of <strong>letter</strong>s between Rahn <strong>an</strong>d Oldenburg; in that sense<br />
it may be regarded both as a rather solitary item <strong>an</strong>d, in effect, as a failure. Nevertheless,<br />
the origins of this <strong>letter</strong> were far <strong>from</strong> solitary; underst<strong>an</strong>ding its full s<strong>to</strong>ry involves tracing<br />
relations between Oldenburg <strong>an</strong>d no fewer th<strong>an</strong> three other Fellows of The Royal<br />
Society—Theodore Haak, John Pell <strong>an</strong>d John Collins. And the <strong>letter</strong> also possesses, in<br />
addition <strong>to</strong> its intrinsic interest, some value as a case-study, illustrating the nature of some<br />
of the problems Oldenburg confronted when his role as a correspondent brought his personal<br />
obligations <strong>an</strong>d his professional duties in<strong>to</strong> conflict.<br />
249 © 2004 The Royal Society
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