Dicuilus (Irish language: Dícuil; Floruit.814–825 Anno Domini) was an Irish monk, astronomer, geographer and author born during the second half of the 8th century, possibly in the Hebrides.Noble, Gordon & Evans, Nicholas (2022), Picts: Scourge of Rome, Rulers of the North, Birlinn, Edinburgh, pp. 273 & 274, He travelled the Frankia around the turn of the 9th century and was involved with the Carolingian Renaissance under Louis the Pious. He was the author of Astronomy and cosmographical treatises during the early 9th century, an example of Hiberno-Latin culture.
In book 7 chapter 6, Dicuil describes Ireland as "our own island" and how he had at times lived in the Hebrides:
We do not read of islands being found in the sea west or north of Spain. There are islands around our own island Hibernia, some small and some very small. Near the island Britannia are many islands, some large, some small, and some medium-sized. Some are in the sea to her 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.
Dicuil's reading was wide; he quotes from, or refers to, thirty Greek and Latin writers, including the classical Homer, Hecataeus, Herodotus, Thucydides, Virgil, Pliny and King Juba, the late classical Solinus, the patristic St Isidore and Orosius, and his contemporary the Irish poet Coelius Sedulius. In particular, he professes to utilize the alleged surveys of the Roman world executed by order of Julius Caesar, Augustus and Theodosius II.
Based on similarities of style, it has been suggested that Dicuil may be the same person as the anonymous Hiberno-Latin poet and grammarian known as Hibernicus exul.
Book 1 contains material on calendars, on 19-year lunar cycles, and on versification. It also contains an account of the two methods of calculating triangular numbers: by summation of the natural numbers, or by the multiplication together of two consecutive numbers divided by two Ross, H.E. & Knott, B.I."Dicuil (9th century) on triangular and square numbers."
Book 2 contains material on the distance between the Earth and the heavens, and between the seven planets; methods for counting the lunar months; the monthly age of the moon; rules for calculating Easter and Lent; intercalary days (extra days) and subtracted days; solar and lunar years; more on versification.
Book 3 contains material on cycles of the stars; 19 year lunar cycles; other large cycles of the Sun and Moon; the first day of the natural year (the spring equinox in March).
Book 4 contains material on solar intercalary days and lunar subtracted days; and on the relative speed of travel of the Moon, Sun and stars.
In the nine sections he treats successively of Europe, Asia, Africa, Egypt, and Ethiopia, the area of the Earth's surface, the five great rivers, certain islands, the length and breadth of the Tyrrhenian Sea, and the six (highest) mountains.
Although mainly a compilation, this work is not without value. Dicuil is our only source for detailed information of the surveys performed by order of Theodosius II; his quotations, generally exact, are of service for the textual criticism of the authors mentioned; of great interest, too, are the few reports which he got from the travellers of his time; as, for instance, from the monk Fidelis who (possibly in 762 AD) journeyed along the canal then still existing, between the River Nile and the Red Sea; and from clerics who had visited the Faroe Islands and lived possibly in Iceland for six months during the summer of 795. Among their claims are the perpetual day at midsummer in "Thule," where there was then "no darkness to hinder one from doing what one would." They also described navigating the sea north of Iceland on their first arrival, and found it ice-free for one day's sail.
Tierney's 1967 edition is currently the only complete translation of the work into English.
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De mensura Orbis terrae
Publication history
Manuscripts
Later medieval manuscripts also exist such as Bodleian Library MS. Canon. Misc. 378 (copied in 1436).
+Manuscripts of the Mensura Orbis
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!Folios
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!Souce P BnF Lat. 4806 25r–40r late 9th Extant D Saxon State and University Library Dresden De 182 50v–62v 9th – 10th Destroyed during the Bombing of Dresden Sigma Cathedral Library of Speyer Codex Spirensis early 10th Lost
Published editions
Notes
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