Gerland the Computist (d.1102?)
Four leaves from Computus Gerlandi, in Latin, decorated manuscript on vellum [France or England, c.1200]
An early witness to a rare computational text: Gerland the Computist’s Computus.

c.150-170 x c.90-102mm. 4 leaves, modern foliation, 39 lines of text in a tiny calligraphic minuscule, blind-ruled, 2 of the leaves with computational calendars and a diagram with key, initials in red or blue (cockled, faded and stained, some margins folded over, a few wormholes and frayed edges).

Provenance:
Colker MS 445; acquired in 1993 from Quaritch.

The text of the present leaves was ascribed by Colker to ‘Garlandus’, or Gerland the Computist, an early medieval logician, astronomer, and mathematician of the 11th-century school of Liège, not to be confused with Gerland of Besançon. The Computus Gerlandi, which is an evolution of the medieval art of calculating the dates of Easter into a more complex science of time reckoning grounded in mathematics and astronomy, survives in some 37 manuscript copies of varying degrees of completeness, of which at least half were written in or around 1200. Gerland is frequently mentioned by other medieval computists of the period, and his great accomplishment was his revision of the Christian era, more specifically his conclusion that the astronomical and calendrical data associated with Christ’s crucifixion mandated changing the dates of his life to AD 8-42. Gerland draws heavily on Bede’s classic textbook De Temporum Ratione: we see this in f.1v, for example, with the paragraph beginning ‘Bissexti diem in mense Februario placuit interkalare romanis’ taken verbatim from De Temporum Ratione XL.1, and the one beginning ‘Quot horis luna [...] luceat’ from XXIV. Folio 2 corresponds to ff.146-7 in one of the earlier surviving manuscripts of Gerland, Paris BnF Latin 15170. The most recent, and only, edition of the Computus Gerlandi is A. Lohr, Der Computus Gerlandi, 2013.

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