Monks, Manuscripts and Sundials

The Navicula in Medieval England


The navicula sundial, because of its rarity and attractive form, has interested curators and historians alike: Derek J. de Solla Price described it as “one of the most ingenious and sophisticated mathematical artefacts of the Middle Ages”. Although apparently a specifically English instrument, there is much debate about when and where it was invented, and about who made and used the five surviving medieval examples. This book brings together for the first time evidence from the surviving instruments, and written sources including four previously unknown texts describing how to make or use the instrument, along with previously unknown copies of the text on which previous studies were based.

Medieval and Early Modern Science, 11
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Biographical Note

Catherine Eagleton, PhD (2005) in History of Science, University of Cambridge, is a curator at the British Museum and an Affiliated Research Scholar at the Department of History and Philosophy of Science, University of Cambridge.

Review Quotes

Thanks to this excellent study we now have a very complete working tool that allows us to know all the ingenuity embedded in these rare sundials.
Denis Savoie, Journal for the History of Astronomy, xliii (February 2012), pp. 120-122

Eagleton has substantially advanced our knowledge of this curious instrument. [...] Her book provides much new grist for the scholarly mill, thanks to the new light it sheds on the interface between artefacts, texts, practices and problems of transmission.
Michael H. Shank, University of Wisconsin-Madison, British Journal for the History of Science, 2011, December, pp. 580-581

Table of contents

List of figures

1. Monks, manuscripts and sundials: the navicula in medieval England
2. Five fifteenth-century sundials
3. Manuscript sources about the navicula
4. Calendar tables and latitude lists
5. Texts, instruments, diagrams and relations between them
6. Using a sundial, understanding the heavens?
7. The navicula and the organum ptolomei
8. How sixteenth-century books redefined a medieval sundial

Appendix One Group A manuscripts
Appendix Two Group A manuscripts
Appendix Three Group A manuscripts
Appendix Four Group A stemmatics
Appendix Five The group B navicula manuscripts
Appendix Six The group C navicula manuscript
Appendix Seven The group D navicula manuscript
Appendix Eight The group E navicula text
Appendix Nine Organum Ptolomei ita sit…



Instrument scholars, including serious amateurs who are members of scientific instrument and sundial societies. Medieval historians and historians of science.


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