Dicuilus (or the more vernacular version of the name Dícuil) was an Irish monk and geographer, born during the second half of the 8th century.

Background

The exact dates of Dicuil's birth and death are unknown. Of his life nothing is known except that he probably belonged to one of the numerous Irish monasteries of the Frankish Kingdom, and became acquainted by personal observation with islands near

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe ...

and

Scotland Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to ...

. From 814 and 816 Dicuil taught in one of the schools of

Louis the Pious Louis the Pious (german: Ludwig der Fromme; french: Louis le Pieux; 16 April 778 – 20 June 840), also called the Fair, and the Debonaire, was King of the Franks and co-emperor with his father, Charlemagne, from 813. He was also King of Aqu ...

, where he wrote an astronomical work, and in 825 a geographical work. Dicuil's reading was wide; he quotes from, or refers to, thirty Greek and Latin writers, including the classical

Homer Homer (; grc, Ὅμηρος , ''Hómēros'') (born ) was a Greek poet who is credited as the author of the ''Iliad'' and the ''Odyssey'', two epic poems that are foundational works of ancient Greek literature. Homer is considered one of the ...

, Hecataeus,

Herodotus Herodotus ( ; grc, , }; BC) was an ancient Greek historian and geographer from the Greek city of Halicarnassus, part of the Persian Empire (now Bodrum, Turkey) and a later citizen of Thurii in modern Calabria (Italy). He is known fo ...

Thucydides Thucydides (; grc, , }; BC) was an Athenian historian and general. His '' History of the Peloponnesian War'' recounts the fifth-century BC war between Sparta and Athens until the year 411 BC. Thucydides has been dubbed the father of " scienti ...

Virgil Publius Vergilius Maro (; traditional dates 15 October 7021 September 19 BC), usually called Virgil or Vergil ( ) in English, was an ancient Roman poet of the Augustan period. He composed three of the most famous poems in Latin literature: th ...

, Pliny and King Juba, the late classical

Solinus Solinus may refer to: * Gaius Julius Solinus, a 3rd century Latin author * Solinus (horse), a British racehorse (1975–1979) * Solinus, Duke of Ephesus, a character in William Shakespeare's play ''The Comedy of Errors'' See also * Salinas (disam ...

, the patristic St Isidore and

Orosius Paulus Orosius (; born 375/385 – 420 AD), less often Paul Orosius in English, was a Roman priest, historian and theologian, and a student of Augustine of Hippo. It is possible that he was born in ''Bracara Augusta'' (now Braga, Portugal), t ...

, and his contemporary the Irish poet Sedulius. In particular, he professes to utilize the alleged surveys of the Roman world executed by order of

Julius Caesar Gaius Julius Caesar (; ; 12 July 100 BC – 15 March 44 BC), was a Roman general and statesman. A member of the First Triumvirate, Caesar led the Roman armies in the Gallic Wars before defeating his political rival Pompey in a civil war, an ...

Augustus Caesar Augustus (born Gaius Octavius; 23 September 63 BC – 19 August AD 14), also known as Octavian, was the first Roman emperor; he reigned from 27 BC until his death in AD 14. He is known for being the founder of the Roman Pr ...

and

Theodosius II Theodosius II ( grc-gre, Θεοδόσιος, Theodosios; 10 April 401 – 28 July 450) was Roman emperor for most of his life, proclaimed ''augustus'' as an infant in 402 and ruling as the eastern Empire's sole emperor after the death of his ...

. Based on similarities of style, it has been suggested that Dicuil may be the same person as the anonymous

Hiberno-Latin Hiberno-Latin, also called Hisperic Latin, was a learned style of literary Latin first used and subsequently spread by Irish monks during the period from the sixth century to the tenth century. Vocabulary and influence Hiberno-Latin was notabl ...

poet and grammarian known as '' Hibernicus exul''.

Astronomical computus

The astronomical work is a sort of

computus As a moveable feast, the date of Easter is determined in each year through a calculation known as (). Easter is celebrated on the first Sunday after the Paschal full moon, which is the first full moon on or after 21 March (a fixed approx ...

of five books, in prose and verse. Four books are preserved in a manuscript which belonged formerly to the monastery of Saint-Amand in northern France, and is now at

Valenciennes Valenciennes (, also , , ; nl, label=also Dutch, Valencijn; pcd, Valincyinnes or ; la, Valentianae) is a commune in the Nord department, Hauts-de-France, France. It lies on the Scheldt () river. Although the city and region experienced a ...

.Hartig, Otto. "Dicuil." The Catholic Encyclopedia. Vol. 4. New York: Robert Appleton Company, 1908. 18 Feb. 2015
/ref> A second manuscript is from the abbey of Saint Martin at Tours, and contains two chapters added to the fourth book, and two more chapters constituting a fifth book Cordoliani, A. "Le comput de Dicuil", Cahiers de civilisation médiéval, 3/11, 1960, 325-337 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 A triangular number or triangle number counts objects arranged in an equilateral triangle. Triangular numbers are a type of figurate number, other examples being square numbers and cube numbers. The th triangular number is the number of dots i ...

: 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." British Journal for the History of Mathematics, 2019,34 (2), 79-94. https://doi.org/10.1080/26375451.2019.1598687. 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 Intercalation or embolism in timekeeping is the insertion of a leap day, week, or month into some calendar years to make the calendar follow the seasons or moon phases. Lunisolar calendars may require intercalations of both days and months. ...

(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.

''De mensura Orbis terrae''

Better known is the ''De mensura Orbis terrae'', a summary of geography, giving concise information about various lands. This work was based upon a ''Mensuratio orbis'' prepared by order of Emperor

(AD 435), a manuscript copy of which was possessed by the

Carolingian The Carolingian dynasty (; known variously as the Carlovingians, Carolingus, Carolings, Karolinger or Karlings) was a Frankish noble family named after Charlemagne, grandson of mayor Charles Martel and a descendant of the Arnulfing and Pippi ...

court. Godescalc had already made use of this copy (781-783) for the composition of his celebrated '' Evangelistarium''. Dicuil uses

Pliny the Elder Gaius Plinius Secundus (AD 23/2479), called Pliny the Elder (), was a Roman author, naturalist and natural philosopher, and naval and army commander of the early Roman Empire, and a friend of the emperor Vespasian. He wrote the encyclopedic ' ...

Gaius Julius Solinus Gaius Julius Solinus was a Latin grammarian, geographer, and compiler who probably flourished in the early 3rd century AD. Historical scholar Theodor Mommsen dates him to the middle of the 3rd century. Solinus was the author of ''De mirabilibus mu ...

Paulus Orosius Paulus Orosius (; born 375/385 – 420 AD), less often Paul Orosius in English, was a Roman priest, historian and theologian, and a student of Augustine of Hippo. It is possible that he was born in ''Bracara Augusta'' (now Braga, Portugal), th ...

Isidore of Seville Isidore of Seville ( la, Isidorus Hispalensis; c. 560 – 4 April 636) was a Spanish scholar, theologian, and archbishop of Seville. He is widely regarded, in the words of 19th-century historian Montalembert, as "the last scholar of ...

, and other authors, and adds the results of his own investigations. In the nine sections he treats successively of

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an are ...

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

Egypt Egypt ( ar, مصر , ), officially the Arab Republic of Egypt, is a List of transcontinental countries, transcontinental country spanning the North Africa, northeast corner of Africa and Western Asia, southwest corner of Asia via a land bridg ...

, and

Ethiopia Ethiopia, , om, Itiyoophiyaa, so, Itoobiya, ti, ኢትዮጵያ, Ítiyop'iya, aa, Itiyoppiya officially the Federal Democratic Republic of Ethiopia, is a landlocked country in the Horn of Africa. It shares borders with Eritrea to the ...

, the area of the Earth's surface, the five great rivers, certain islands, the length and breadth of the

Tyrrhenian Sea The Tyrrhenian Sea (; it, Mar Tirreno , french: Mer Tyrrhénienne , sc, Mare Tirrenu, co, Mari Tirrenu, scn, Mari Tirrenu, nap, Mare Tirreno) is part of the Mediterranean Sea off the western coast of Italy. It is named for the Tyrrhenian pe ...

, 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 CE) journeyed along the canal then still existing, between the River

Nile The Nile, , Bohairic , lg, Kiira , Nobiin: Áman Dawū is a major north-flowing river in northeastern Africa. It flows into the Mediterranean Sea. The Nile is the longest river in Africa and has historically been considered the longest riv ...

and the

Red Sea The Red Sea ( ar, البحر الأحمر - بحر القلزم, translit=Modern: al-Baḥr al-ʾAḥmar, Medieval: Baḥr al-Qulzum; or ; Coptic: ⲫⲓⲟⲙ ⲛ̀ϩⲁϩ ''Phiom Enhah'' or ⲫⲓⲟⲙ ⲛ̀ϣⲁⲣⲓ ''Phiom ǹšari''; ...

; and from clerics who had visited the

Faroe Islands The Faroe Islands ( ), or simply the Faroes ( fo, Føroyar ; da, Færøerne ), are a North Atlantic island group and an autonomous territory of the Kingdom of Denmark. They are located north-northwest of Scotland, and about halfway bet ...

and lived possibly in

Iceland Iceland ( is, Ísland; ) is a Nordic island country in the North Atlantic Ocean and in the Arctic Ocean. Iceland is the most sparsely populated country in Europe. Iceland's capital and largest city is Reykjavík, which (along with its ...

for six months during the summer of 795. Among their claims are the perpetual day at midsummer in "

Thule Thule ( grc-gre, Θούλη, Thoúlē; la, Thūlē) is the most northerly location mentioned in ancient Greek and Roman literature and cartography. Modern interpretations have included Orkney, Shetland, northern Scotland, the island of Saar ...

," 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.

Editions

The geography manuscript was known to Marcus Welser, Isaac Vossius,

Claudius Salmasius Claude Saumaise (15 April 1588 – 3 September 1653), also known by the Latin name Claudius Salmasius, was a French classical scholar. Life Salmasius was born at Semur-en-Auxois in Burgundy. His father, a counsellor of the parlement of Dijon, se ...

, Jean Hardouin, and

Johann Daniel Schöpflin Johann Daniel Schöpflin (6 September 1694, Sulzburg – 7 August 1771, Strasbourg) was a professor of history, rhetoric and law at the University of Strasbourg. He was one of Johann Wolfgang von Goethe’s teachers. Biography Schöpflin was w ...

; it was first printed with the title: ''Dicuili Liber de mensura orbis terrae ex duobus codd. mss. bibliothecae imperialis nunc primum in lucem editus a Car. Athan. Walckenaer'' (Paris, 1807). *J. J. Tierney, ''Dicuil: Liber de Mensura Orbis Terrae'', (Dublin 1967).

Notes

References

* {{DEFAULTSORT:Dicuil Irish Christian monks Irish explorers 9th-century Irish poets 8th-century Irish writers 9th-century Irish writers 9th-century Latin writers Irish astronomers Irish expatriates in France Irish male poets Irish Latinists Carolingian poets 9th-century astronomers Irish scholars and academics