IMPROVING INSTRUMENTS: EQUATORIA, ASTROLABES, AND THE PRACTICES OF MONASTIC ASTRONOMY IN LATE MEDIEVAL ENGLAND Sebastian Leonard Dundas Falk Peterhouse This dissertation is submitted for the degree of Doctor of Philosophy February 2016 This dissertation is the result of my own work and includes nothing which is the outcome of work done in collaboration. It is not substantially the same as any that I have submitted, or, is being concurrently submitted for a degree or diploma or other qualification at the University of Cambridge or any other University or similar institution. I further state that no substantial part of my dissertation has already been submitted, or, is being concurrently submitted for any such degree, diploma or other qualification at the University of Cambridge or any other University of similar institution. It does not exceed 80,000 words, including footnotes but excluding the appendix as approved by the Degree Committee of the Department of History and Philosophy of Science. The Equatorie of the Planetis Peterhouse, Cambridge MS 75.I, f. 74r. Quaerite . facientem Arcturum et Orionem Amos 5:6-8 (Vulgate) Seek him that maketh the seven stars and Orion Amos 5:8 (King James Version) He who made the Pleiades and Orion Amos 5:8 (New International Version) IMPROVING INSTRUMENTS: EQUATORIA, ASTROLABES, AND THE PRACTICES OF MONASTIC ASTRONOMY IN LATE MEDIEVAL ENGLAND Histories of medieval astronomy have brought to light a rich textual tradition, of treatises and tables composed and computed, transmitted and translated across Europe and beyond. These have been supplemented by fruitful inquiry into the material culture of astronomy, especially the instruments that served as models of the heavens, for teaching and for practical purposes. But even now we know little about the practices of medieval astronomers: how they obtained and passed on their knowledge; how they drew up and used mathematical tables; how they drafted the treatises in which they found words to express their ideas and inventions for their particular audiences. This thesis uses a case study approach to elucidate these medieval astronomical practices. Long thought to be a holograph manuscript in the hand of Geoffrey Chaucer, the Equatorie of the Planetis (Peterhouse, Cambridge MS 75.I) has recently been identified as the work of John Westwyk (d. c. 1400), a Benedictine monk of Tynemouth Priory and St Albans Abbey. His draft description of the construction and use of an astronomical instrument, with accompanying tables, provides an opportunity to reconstruct the practices of an unexceptional astronomer. The first chapter of this thesis reconstructs Westwyk’s astronomical reading and understanding, through an examination of the other manuscript that survives in his hand: a pair of instrument treatises by the outstanding monastic astronomer Richard of Wallingford. I show how Westwyk copied this manuscript in a monastic context, learning as he annotated texts and recomputed tables. In the second chapter I discuss the purposes of planetary instruments such as equatoria, their place among other astronomical instruments, and the physical constraints and possibilities experienced by their makers. Through this discussion I assess the craft environment in which Westwyk came to write his own instrument-making instructions. Chapters three and four assess Westwyk’s language, explaining the basis for his choice to write a technical work in the vernacular, and analysing how his innovative use of Middle English furthered his didactic objectives. In the final chapter, I undertake a technical reassessment of the Equatorie treatise, an integrated analysis of the instrument with the somewhat neglected tables that Westwyk compiled alongside it. The thesis thus applies a range of methodologies to examine the practices and products of a single inexpert astronomer from all angles. It aims to show what an in-depth case study approach can offer historians of the medieval sciences. i ACKNOWLEDGEMENTS My doctoral research has been funded by the Arts and Humanities Research Council, whose support I gratefully acknowledge. I would like to thank my supervisor, Liba Taub, for first bringing the Equatorie to my attention, for introducing me to the possibilities of working with museums and their collections, and for encouraging me throughout my time in Cambridge. Likewise Nick Jardine, my advisor, has been very supportive in my attempts to understand the trepidation of the eighth sphere and the ablative of respect. I am very grateful to them both. I have benefited hugely from the help of a large number of people who have provided expert advice, and of whose scholarship I remain in awe. Scott Mandelbrote shared his knowledge of the Peterhouse manuscripts, and wisely directed the Equatorie reconstruction project; in that project, Ben Blundell was an energising partner. Kari Anne Rand offered patient, encouraging advice on John Westwyk and his manuscripts; Jacob Currie lent his expertise on St Albans. Tessa Webber and Debby Banham provided palaeographic assistance, and my fellow Latin Therapists added tea, romance and grammatical precision. John Davis kindly shared the results of his XRF analyses, and Daniel Wagner offered timely trigonometric tuition. The family of Derek de Solla Price supplied abundant memories and memorabilia of their father. Katie Eagleton shared her knowledge of medieval instruments and the texts describing them, and Linda Voigts provided helpful advice on the vernacular and its users. I was fortunate to be able to refine my ideas at many workshops and conferences, and am grateful to innumerable inquisitive scholars who instigated or supported my attendance, asked thought-provoking questions, and corresponded thereafter; while it is invidious to name just a few individuals, I would particularly like to acknowledge the support of José Chabás, Karine Chemla, Margaret Gaida, Matthieu Husson, Boris Jardine, Rich Kremer, Jenny Rampling, Richard Thomason and Glen Van Brummelen. Susannah Gibson, Matthieu Husson, Peter Jones, Rich Kremer, Lea Olsan, Richard Oosterhoff and the members of the HPS History Workshop gave very helpful feedback on draft chapters. The Department of History and Philosophy of Science has been a fantastic place to work for the past five years, and I would like to thank its administrative team, as well as the staff of the Whipple Library and Whipple Museum, especially Steve Kruse, Josh Nall and Claire Wallace. I have been fortunate in the assistance I have received from many other archives and repositories, and I would particularly like to thank the staff of: Cambridge University Library and the libraries of Corpus Christi, Gonville & Caius and Trinity Colleges; the Bodleian Library, Oxford, and the libraries of Corpus Christi and Merton Colleges (especially Julia Walworth); the libraries of the universities of Aberdeen and Salamanca; the Adler Planetarium, Chicago; the British Museum; and the Museum of the History of Science, Oxford (especially Silke Ackermann and Stephen Johnston). I am most grateful for the support I have received in various forms from all at Peterhouse. And my final and greatest debt is owed to my family, who have fed, clothed and supported me, provided welcome distraction, and kept my feet warm through the years. iii TABLE OF CONTENTS Abstract i Acknowledgements iii List of figures vii List of tables ix Introduction 1 1 Writing astronomy in a monastic environment: how John Westwyk 13 compiled his Wallingford MS Laud Misc 657: the Albion and Rectangulus 14 Monasteries, books, astronomy 16 John Westwyk, copying and compilation 20 Collation and understanding 23 Ascensions and houses 33 Saphea, astrolabe, Albion 37 Conclusion 40 2 Never fixed, never finished: astrolabes as supports for planetary calculators 43 Why the backs of astrolabes? 46 Equatoria on the backs of astrolabes 57 What else might be on the back of an astrolabe? 67 Conclusion 74 3 Late medieval language choice: the scientific vernacular and John Westwyk 77 Westwyk’s naked wordes: situating the author 79 Time and place: John Westwyk’s nameless self-identification 85 ‘Nota: I conseile the...’: the audience for English 88 What was English for? The domains of the Equatorie of the Planetis 90 Practical and pedagogical purposes 92 Conclusion 97 4 ‘I shal teche the aremedie’: crafting the vernacular 101 Didactic definitions 103 Learning opportunities 106 Vocabulary and stylistic innovation 113 Conclusion 118 v 5 Learning through instrument and tables: the content of the Equatorie of the 121 Planetis The Equatorie: instrument and tables 123 The equatorium and tables: apt to be used together 133 Calculation and copying; precision and accuracy 135 ‘This canon is fals’: longitude problems 141 Experimentation for learning 147 Conclusion 154 Conclusion 157 Appendix A Original Latin and Middle English passages quoted in translation in this thesis 163 B Excerpt from Oxford, Bodleian Library MS Laud Misc. 657 167 C Tables and Formulae: C.1 Tables in Oxford, Bodleian Library MS Laud Misc. 657 171 C.2 Differing values in tables of oblique ascensions for 51° 50' 172 C.3 Analysis of obliquities used to compute tables of oblique ascensions 173 C.4 Transcription of MS Laud Misc. 657, f. 42v 174 C.5 Analysis of table of oblique ascensions for 55° (Tynemouth) 175 C.6 Equations used to compute houses, given longitude of midheaven (λ10) 177 C.7 Transcription of MS Laud Misc. 657, ff. 44v-45r 178 D Quia nobilissima scientia astronomie 181 E Medii motus planetarum 195 F Excerpt from University of Aberdeen MS 123 200 G Some noteworthy technical terms used in Peterhouse MS 75.I, with Latin and Arabic equivalents: G.1 Words explicitly defined by John Westwyk (using the verbs callen or clepen) 203 G.2 Words that make their first recorded appearance in Peterhouse MS 75.I 204 G.3 Other noteworthy terms 205 Bibliography Instruments, manuscripts and archival sources 207 Printed works 208 vi LIST OF FIGURES Page Frontispiece: The equatorie of the planetis. Peterhouse, Cambridge MS 75.I, f. 74r. Reproduced by permission of the Master and Fellows of Peterhouse, Cambridge 1 The “Chaucer radix”.