DICUIL (Medieval Ireland)

Dicuil (c. 760-post 825) was an Irish scholar-exile at the courts of Charles the Great and Louis the Pious, and an important author of several works on geography, computus, grammar, and astronomy. The only details known of his life are what can be garnered from incidental references in his works. He was teacher at the Palace School of Louis the Pious in about 815. The date of Dicuil’s death is not known.

His first work, Liber de astronomia, is a verse-computus written between 814 and 816 in four books, to which a fifth book was later added. In 818, he wrote the Epistula censuum, a verse treatise on weights and measures. He also made a copy of Priscian’s Parti-tiones XII Versuum Aeneidos Principalium, which he summarized in twenty-seven hexameters appended to it. He also wrote an Epistola de questionibus decim artis grammaticae, which no longer survives.

In 825, he wrote two treatises, De prima syllaba, a tract on prosody, and Liber de mensura orbis terrae, a treatise on geography and unquestionably his most important work. Dicuil used a wide range of sources, directly or indirectly, for this treatise. Some of these are now lost or only partly preserved, such as the Cosmographia of Julius Caesar in the recension of Julius Honorius, as well as some derivative of the emperor Agrippa’s map of the world, probably that known as the Diuisio (or Mensuratio) orbis of emperor Theodosius. Among his other sources are Pliny the Elder, Solinus, Isidore of Seville, and Caelius Sedulius. He had clearly spent some time in the islands north of Britain and Ireland. As he says himself: "Near the island Britannia are many islands, some large, some small, and some medium-sized. Some are in her sea south and some in the sea to her west, but they abound mostly to the north-west and north. Among these I have lived in some, and have visited others; some I have only glimpsed, while others I have read about." (Liber de mensura orbis terrae VII § 6)

Dicuil tells us that he was present when a monk, who had returned from a pilgrimage to the Holy Land sometime before 767, was received by Suibne on Iona. This "master Suibne" to whom Dicuil refers was most likely Suibne, abbot of Iona from 767 to 772. Dicuil had acquired his geographical knowledge of the islands around Britain from some time spent as a monk on Iona, and from first-hand oral accounts of the voyages of Irish hermit-monks in the eighth century to the islands north of Britain, to the Orkneys, Shetlands, and Faroes, and to Iceland (Thule), where they sojourned from February to August. Some of the islands—perhaps the Faroes—had been occupied by Irishmen "for nearly a hundred years." His description of the eastern Mediterranean, including Egypt and Palestine, is largely derived from written sources, though he also refers to oral information communicated from a traveler to those parts, a "brother Fidelis," from whom he also got one of the earliest descriptions in Western vernacular literature of a Nile crocodile!