London, British Library, MSS Cotton Caligula A.XV, fols. 120r–153v + Egerton 3314, fols. 1r–44v

This book, a computus manuscript produced soon after 1073 at the Benedictine priory attached to Christ Church Cathedral, Canterbury, provides us with a relatively straightforward example of an Easter Table with annals in its margin. The tables are found on folios 132v–139r of Cotton Caligula A.XV. They originally covered the years 988 to 1193, ending on folio 138r. Its format spans two facing pages, and a generous margin has been left on the right-hand side of each opening, apparently so that the annals could be accommodated there. An additional line for the year 925 was added above the table on 132v–133r. On the two blank pages (138v–139r) following the original table, a twelfth-century hand added year-numbers 1194–1267, and a later hand added the year-number 1268 and filled in computistical data for the years 1194–1268. In the original hand the annals extend as far as 1073. Thereafter the annals, being kept up at irregular intervals for more than a century, are the work of at least eighteen different hands.

firebeastThough its significance and purpose remain obscure, this form of annal-keeping is widely attested throughout the Middle Ages. Indeed, it was once a widely view that the art of historical writing was re-discovered in the Middle Ages, after it had disappeared amid the fall of Rome, by monks making use of such tables. Consulting these tables to know the date of Easter in the current year, they would (so the theory goes) note in the margin a few recent events that seemed significant. These marginal notations were developed, then copied out and continued on their own account, without the Paschal table but keeping the number of the year. Part of the attraction of this theory is that it helps to explain the spread of anno-domini dating, ‘in-the-year-of-the-Lord’ dating, a development which only begins in the eighth century. The key point here is that the Easter Tables of Dionysius Exiguus (‘Denis the Dwarf’), which, thanks to Bede, were widely recognised as the most accurate from the eighth century onwards, took the year of the Incarnation of Jesus Christ as their starting point. This view has, however, been challenged from many different directions in recent work.

The book in which the present example is found is a miscellany of texts, tables and diagrams which were employed in the science of ‘computus’ (or ‘sacred mathematics’), a discipline chiefly concerned with measurement of time in all its forms, but which also embraced the study of all aspects of the natural world. This example has, among many other items, instructions for how to find the date of Easter and of other moveable feasts (Eggerton 3314, fols. 9r–12v), a treatise on the order and length of the months by Herman the Lame (fols. 14–17v), an astronomical calendar with lunar tables (fols. 18v–30r), a table of lunar cycles for the years 1064–1577 (fol. 31v), and so on. Like Oxford, St John’s College, MS 17, this computus collection includes a few medical texts, the most notable of which is a Old Norse charm against the poisoning of the blood with pus. Written in runes at the foot of Cotton Caligula A.XV, fols. 123v–124r, this charm is notorious for its invocation of the pagan god Thor.

The original volume probably began life as a set of booklets, various items being added to it, the most notable of these additions being a treatise on how the concurrents for any given year may be found by counting with the fingers on your hands (Quomodo inueniri possint concurrentes cuiuslibet anni per manum: Egerton 3314, fols. 73r–75v). This item was added in the late twelfth century (probably in 1185) by a Christ-Church monk called Salomon who may have been responsible for arranging the booklets and for having them bound as a single book. As reconstructed by Willetts, this book was arranged as follows: (1) Egerton 3314, fols. 1–8; (2) Caligula A.XV, fols. 120–141; (3) Egerton 3314, fols. 9–13; (4) Egerton 3314, fols. 14–44; (5) Caligula A.XV, fols. 143–153; (6) Egerton 3314, fols. 45–75, and (7) Egerton 3314, fols. 76–78. The book is described as the Compotus Adelardi in the catalogue of books in the library of Christ Church compiled by or for Prior Eastry in the early 14th-century. The words Adthelardus de compoto appear in the upper margin of the first folio.

It is unclear when the book was broken up, but it seems likely that its dismemberment took place after the dissolution of Christ Church Cathedral Priory (1539). Computus manuscripts were often dismembered and re-organised for new purposes in the sixteenth and seventeenth centuries, the result being that few survive in their entirety. The portions which were incorporated into Egerton 3314 certainly belonged to the Elizabethan scholar Dr John Dee (1527–1608): it was his practice to inscribe his books with the astrological symbol for Jupiter, and just such a symbol appears in the upper right hand corner of the first folio. It was purchased by the British Museum in 1945.


Facsimile: Folios 132v–133r are reproduced in G. N. Garmonsway (trs.), The Anglo-Saxon Chronicle (London, 1953), pp. xxiv–xxv. Garmonsway also translates the Old English items at ibid., pp. 270–2.

Text: P. Baker (ed.), The Anglo-Saxon Chronicle: A Collaborative Edition, vol. 8, MS F (Cambridge, 2000), pp. 129–34. MVC.

Commentary: The British Library MSS catalogue has a useful description of Egerton 3088 with links to various images, mostly from the same portions of the book. For the entry in Prior Eastry’s library catalogue, see M. R. James, Ancient Libraries of Canterbury and Dover (Cambridge, 1903), p. 49 (no. 287); B. C. Barker-Benfield (ed.), Corpus of British Medieval Library Catalogues, vol. 13, St Augustine’s Abbey, Canterbury, 3 pts. (London, 2008) [ZVRea2]. For a fuller account of the history of the book, see P. J. Willetts, ‘A Reconstructed Astronomical Manuscript from Christ Church Library, Canterbury’, British Museum Quarterly, 30 (1965–66), 22–30 [JSTOR]; and for the calendar, see R. Rushforth, Saints in English Kalendars before AD 1100, Henry Bradshaw Society 117 (Woodbridge, 2008), no. 26 (pp. 52–53). See also A. G. Watson, Catalogue of Dated and Datable Manuscripts c. 700-1600 in The Department of Manuscripts: The British Library, 2 vols (London, 1979), i, no. 517.

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