Dicuilus ( Gaelic: ; fl.814-825 A.D.) was an Irish monk, astronomer,

geographer A geographer is a physical scientist, social scientist or humanist whose area of study is geography, the study of Earth's natural environment and human society, including how society and nature interacts. The Greek prefix "geo" means "earth" a ...

and author born during the second half of the 8th century, possibly in the

Hebrides The Hebrides ( ; , ; ) are the largest archipelago in the United Kingdom, off the west coast of the Scotland, Scottish mainland. The islands fall into two main groups, based on their proximity to the mainland: the Inner Hebrides, Inner and Ou ...

. He travelled the Frankia around the turn of the 9th century and was involved with the

Carolingian Renaissance The Carolingian Renaissance was the first of three medieval renaissances, a period of cultural activity in the Carolingian Empire. Charlemagne's reign led to an intellectual revival beginning in the 8th century and continuing throughout the 9th ...

under

Louis the Pious Louis the Pious (; ; ; 16 April 778 – 20 June 840), also called the Fair and the Debonaire, was King of the Franks and Holy Roman Emperor, co-emperor with his father, Charlemagne, from 813. He was also King of Aquitaine from 781. As the only ...

. He was the author of

astronomical Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest include ...

and cosmographical treatises during the early 9th century, an example of Hiberno-Latin culture.

Background

The exact dates of Dicuil's birth and death are unknown; indeed all details of his life are known only from his writings. Tierney suggests his birth to be sometime around c.760-770 A.D. 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 Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...

and

Scotland Scotland is a Countries of the United Kingdom, country that is part of the United Kingdom. It contains nearly one-third of the United Kingdom's land area, consisting of the northern part of the island of Great Britain and more than 790 adjac ...

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

, where he wrote an astronomical work, and in 825 a geographical work. In book 7 chapter 6, Dicuil describes

Ireland Ireland (, ; ; Ulster Scots dialect, Ulster-Scots: ) is an island in the North Atlantic Ocean, in Northwestern Europe. Geopolitically, the island is divided between the Republic of Ireland (officially Names of the Irish state, named Irelan ...

as "our own island" and how he had at times lived in the

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 The image of Britannia () is the national personification of United Kingdom, Britain as a helmeted female warrior holding a trident and shield. An image first used by the Romans in classical antiquity, the Latin was the name variously appli ...
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 Homer (; , ; possibly born ) was an Ancient Greece, Ancient 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. Despite doubts about his autho ...

, Hecataeus,

Herodotus Herodotus (; BC) was a Greek historian and geographer from the Greek city of Halicarnassus (now Bodrum, Turkey), under Persian control in the 5th century BC, and a later citizen of Thurii in modern Calabria, Italy. He wrote the '' Histori ...

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

Virgil Publius Vergilius Maro (; 15 October 70 BC21 September 19 BC), usually called Virgil or Vergil ( ) in English, was an ancient Rome, ancient Roman poet of the Augustan literature (ancient Rome), Augustan period. He composed three of the most fa ...

, Pliny and King Juba, the late classical Solinus, the patristic St Isidore and Orosius, 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 or 13 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 Caesar's civil wa ...

Augustus Gaius Julius Caesar Augustus (born Gaius Octavius; 23 September 63 BC – 19 August AD 14), also known as Octavian (), was the founder of the Roman Empire, who reigned as the first Roman emperor from 27 BC until his death in A ...

and

Theodosius II Theodosius II ( ; 10 April 401 – 28 July 450), called "the Calligraphy, Calligrapher", was Roman emperor from 402 to 450. He was proclaimed ''Augustus (title), Augustus'' as an infant and ruled as the Eastern Empire's sole emperor after the ...

. 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''.

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 – often simply ''Computus'' – or as paschalion particularly in the Eastern Orthodox Church. Easter is celebrated on the first Sunday after th ...

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 , , ; ; or ; ) is a communes of France, commune in the Nord (French department), Nord Departments of France, department, Hauts-de-France, France. It lies on the Scheldt () river. Although the city and region experienced ...

.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: 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 (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'', completed in 825 A.D; 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 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 23/24 79), known in English as Pliny the Elder ( ), was a Roman Empire, Roman author, Natural history, naturalist, and naval and army commander of the early Roman Empire, and a friend of the Roman emperor, emperor Vesp ...

Gaius Julius Solinus __NOTOC__ Gaius Julius Solinus, better known simply as 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. ...

, Paulus Orosius,

Isidore of Seville Isidore of Seville (; 4 April 636) was a Spania, Hispano-Roman scholar, theologian and Roman Catholic Archdiocese of Seville, archbishop of Seville. He is widely regarded, in the words of the 19th-century historian Charles Forbes René de Montal ...

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

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...

Africa Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...

Egypt Egypt ( , ), officially the Arab Republic of Egypt, is a country spanning the Northeast Africa, northeast corner of Africa and Western Asia, southwest corner of Asia via the Sinai Peninsula. It is bordered by the Mediterranean Sea to northe ...

, and

Ethiopia Ethiopia, officially the Federal Democratic Republic of Ethiopia, is a landlocked country located in the Horn of Africa region of East Africa. It shares borders with Eritrea to the north, Djibouti to the northeast, Somalia to the east, Ken ...

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

Tyrrhenian Sea The Tyrrhenian Sea (, ; or ) , , , , is part of the Mediterranean Sea off the western coast of Italy. It is named for the Tyrrhenians, Tyrrhenian people identified with the Etruscans of Italy. Geography The sea is bounded by the islands of C ...

, 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 The Nile (also known as the Nile River or River Nile) is a major north-flowing river in northeastern Africa. It flows into the Mediterranean Sea. The Nile is the longest river in Africa. It has historically been considered the List of river sy ...

and the

Red Sea The Red Sea is a sea inlet of the Indian Ocean, lying between Africa and Asia. Its connection to the ocean is in the south, through the Bab-el-Mandeb Strait and the Gulf of Aden. To its north lie the Sinai Peninsula, the Gulf of Aqaba, and th ...

; and from clerics who had visited the

Faroe Islands The Faroe Islands ( ) (alt. the Faroes) are an archipelago in the North Atlantic Ocean and an autonomous territory of the Danish Realm, Kingdom of Denmark. Located between Iceland, Norway, and the United Kingdom, the islands have a populat ...

and lived possibly in

Iceland Iceland is a Nordic countries, Nordic island country between the Atlantic Ocean, North Atlantic and Arctic Oceans, on the Mid-Atlantic Ridge between North America and Europe. It is culturally and politically linked with Europe and is the regi ...

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.

Publication history

Manuscripts

Three prototype manuscripts forming the basis of the textual tradition of the Orbis are known: Later medieval manuscripts also exist such as Bodleian MS. Canon. Misc. 378 (copied in 1436).

Published editions

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

Jean Hardouin Jean Hardouin (; ; ; 23 December 1646 – 3 September 1729), was a French priest and classical scholar who was well known during his lifetime for his editions of ancient authors, and for writing a history of the ecumenical councils. However, he ...

, and Johann Daniel Schöpflin. The three complete editions published so far have been: * * * Tierney's 1967 edition is currently the only complete translation of the work into English.

Notes

References

* {{DEFAULTSORT:Dicuil 8th-century births Year of birth uncertain 9th-century Irish poets 8th-century Irish writers 9th-century writers in Latin 9th-century Christian monks 9th-century astronomers Irish Christian monks Irish explorers Irish astronomers Irish expatriates in France Irish male poets Irish writers in Latin Carolingian poets Irish scholars and academics Medieval Gaels Thule