‘Byrhtferth’s Ogam Signature’ and Oxford, St John’s College MS 17

A close up of a manuscript image where the capital initials AMDA are arranged clockwise around a lozenge shape. In the centre, a circle composed of triplicate ogam letters arranged as wheel spokes are evident.

By Deborah Hayden, OG(H)AM’s Co-Investigator

As we move into a new year, it seems fitting that this January’s OG(H)AM project blog should be devoted to a manuscript source concerned with calendrical matters. The image below is of a page in Oxford, St John’s College MS 17, an early-twelfth-century collection of texts, tables, maps and diagrams produced in the Benedictine monastery at Thorney Abbey in Cambridgeshire, England. The contents of this manuscript are organized around the central theme of computus, the medieval science of calculating times and dates using a combination of mathematics and astronomy. It includes a wide range of material thought to be connected in various ways with the concept of time, such as texts on cosmology, geography, medicine, history, mathematics and prognostication.

A manuscript page as described in text of blog, two lozenges are surrounded by a figure-eight shape which connects many aspects of the year and Adam.
‘Byrhtferth’s Diagram’ in Oxford, St John’s College MS 17, fol. 7v. Image courtesy of the Digital Bodleian Library. For a full description of the contents, scribes and provenance of this manuscript, as well as extensive bibliographical details, see this excellent website.

This folio of the manuscript contains a copy of an ambitious diagram, originally designed by the monk Byrhtferth of Ramsey, that serves symbolically to link elements, seasons, months and zodiacal signs, as well as to illustrate the religious resonances of computus and the connections between macrocosm and microcosm. The text surrounding the diagram explains its contents as follows:

Hanc figuram edidit bryhtferð monachus ramesiensis coenobii de concordia mensium atque elementorum. Hi sunt solares scilicet dicuntur quia secundum ipsum cursum constant menses qui habent dise XXXI : Ianuarius. Martius, Maius, Iulius. Augustus. October. December. Hi autem XXX scilicet dies habent secundum solis cursum: Aprilis. Iunius. September. November. Februarius uero ab omnibus er<r>at. Retinet hec figura XII signa et duo solstitia. atque bina equinoctia. et bisbina tempora anni. in qua descripta sunt IIII nomina elementorum. et duodenorum uentorum onomata. atque IIII etates hominum. Sunt insimul coniuncta<e> bis bine littere nominis protoplasti ade. Demonstrat enim uero quales menses lunam XXX quales XXIX habent.

‘Byrhtferth, monk of Ramsey Abbey, set forth this diagram of the harmony of the months and the elements. These are the solar months (so called because they follow the Sun’s course) which have 31 days: January, March, May, July, August, October, December. These have 30 (that is, days according to the Sun’s course): April, June, September and November. But February deviates from them all. This diagram contains the twelve signs and also the two equinoxes and the twice-two seasons of the year, within which are inscribed the names of the four elements and the designations of the twelve winds, and also the four ages of man. The twice-two letter of the name of Adam, the first-created man, are also added. It shows which months have a moon of 30 <days> and which a moon of 29.’1

Ogam Script in Byrhtferth’s Diagram

At the centre of this diagram (shown in the image detail below) is a diamond pattern with the capital letters ADAM at the four points of the compass. Within this diamond is a wheel-like device that bears a vague resemblance to the form of cryptic ogam known as Traigsruth Ferchertne (?‘Ferchertne’s foot-stream’) in the medieval Irish tract known as In Lebor Ogaim (‘The Book of Ogam’, discussed further here). Above this is a narrow horizontal strip containing an assortment of symbols and a short line of what Faith Wallis has described as ‘Ogham or pseudo-Ogham writing’:

A closer detail image of the ogham in the centre of the manuscript page, with ogam arranged as spokes of a wheel below a band which contains another ogam inscription.
‘Byrhtferth’s Diagram’ in Oxford, St John’s College MS 17, fol. 7v (detail). Image courtesy of the Digital Bodleian Library.

The meaning of these symbols is uncertain and has been a subject of some debate. In one contribution to the discussion, Patrick Sims-Williams suggested that the ogam letters written within the horizontal bar might be read as MEGFDLU, which – if one applies to the final five symbols of the line a common medieval cryptographic practice in which each letter is represented by the one which follows it in the Latin alphabet – might be read as Latin me fecit (‘made me’). The pictograms preceding the line of ogam, Sims-Williams argued, could therefore represent the name of the diagram’s maker, perhaps Byrhtferth of Ramsey himself.

Interpretations of the wheel-like device below this line have likewise varied, but Sims-Williams suggested that the strokes in the centre of the circle, read clockwise, can be transcribed as BBB BBB MMM MMM BBB BBB D MMM. By once again assuming that a letter-substitution cipher has been applied (but this time only to vowels), the writing on the ‘spokes’ of the wheel might be deciphered as AAA AAA MMM MMM AAA AAA D MMM, more or less in agreement with the surrounding Roman capital-letter inscription AAMD. The tripling of the letters inside the wheel also recalls a cryptic variant of the ogam alphabet named in In Lebor Ogaim as Sluag ogam (‘Host ogam’), described in that source as in fid fen do scribend ter (.i. ina thri) aire fen .i. bethi ter (ina thri), luis ter (ina thri), 7rl. (‘the letter itself to be written thrice for itself, i.e. b thrice, l thrice, etc.).2

While Sims-Williams’s argument regarding the interpretation of the ‘ogham or pseudo-ogham’ symbols on folio 7v of St John’s College MS 17 has not been universally accepted, it is interesting to note that a preceding page of the manuscript (folio 5v) contains tables of early runes, exotic alphabets and cryptographic devices, including an illustration of the two letter-substitution ciphers (one for all letters of the alphabet, and one just for vowels) that Sims-Williams argues to be key to deciphering the ogam writing in Byrhtferth’s Diagram:

Another manuscript page with columns of foreign alphabets translated, next to four circles aligned top to bottom and containing further texts.
Early runic, cryptographic and exotic alphabets in Oxford, St John’s College MS 17, fol. 5v. Image courtesy of the Digital Bodleian Library.

Ogam script does not itself number among these alphabets, but there are indications that the cryptographic methods of the Irish scholars who composed In Lebor Ogaim may have been known to the compiler of these tables. In one of the alphabets, for example, vowels are replaced by one to five symbols that resemble majuscule Gs or the Arabic numeral 6: a practice which is reminiscent of the ogam variant known as coll ar guta (‘c for a vowel’), attested in both In Lebor Ogaim and many early modern and modern Irish manuscripts (on which see further here). On a broader level, it might also be noted that the use of the writing system in manuscript sources is closely tied to early ideas about grammar and script systems and that illustrations of ogam script are found alongside other ‘foreign’ or ‘exotic’ alphabets in several early medieval manuscript sources preserved both within and outside of Ireland.

Although Oxford, St John’s College MS 17 does not represent the oldest surviving attestations of manuscript ogam (examples of which are found in a handful of Irish sources from as early as the ninth century), it does constitute intriguing evidence for the spread and use of the script outside of the Gaelic-speaking world and a handful of Irish-influenced centres of learning on the continent. It also suggests that some of the cryptic devices described in In Lebor Ogaim not only pre-date the earliest extant witness of that tract by some two centuries,3 but indeed may have found their way across the Irish Sea and as far as the learned circles of late-tenth-century East Anglia.


[1] Latin text and translation by Faith Wallis available on The Calendar and the Cloister website.

[2] Calder, Auraicept, p. 307 and l. 6021–4.

[3] Found in Dublin, Royal Irish Academy MS 23 P 12 (‘The Book of Ballymote’, late 14th century).

Further reading:

Baker, Peter and Michael Lapidge (eds), Byrhtferth’s Enchiridion, Early English Text Society o.s. 15 (Oxford, 1995)

Calder, George, Auraicept na nÉces. The Scholars’ Primer (Edinburgh, 1917)

Derolez, René, ‘“Ogam”, “Egyptian”, “African », and “Gothic” alphabets: some remarks in connection with Codex Bernensis 207’, Scriptorium 5 (1951), 1–19

Sims-Williams, Patrick, ‘Byrhtferth’s ogam signature’, in Essays and Poems Presented to Daniel Huws, ed. by T. Jones and E. B. Fryde (Aberystwyth, 1994), pp. 283–91

Wallis, Faith, The Calendar and the Cloister website: https://digital.library.mcgill.ca/ms-17/index.htm

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