SCIENCES
Computus and Astronomy
Computistical literature must have been well estab-
lished in Ireland by the sixth century. The basis of their
reckoning of the paschal term was the fourth-century
Latin translation of Anatolius of Laodicea’s,
De
ratione paschali
(“On the reckoning of the Pasch”).
Cumian’s paschal letter to Ségéne in 632/3 refers to
ten different paschal cycles, including Anatolius. The
anonymous seventh-century treatise
De ratione com-
putandi
shows the author to have had a very competent
knowledge of calendrical science and computistics,
Bede and the Anglo-Saxons were deeply indebted to
the Irish for their knowledge of the computus.
The astronomical entries in the Irish annals,
recorded from 627 to 1133, constitute one of the most
extensive and careful series of records in Western
Europe of observations of eclipses, comets, auroras,
volcanic dust clouds, and the supernova of 1054. Such
phenomena were recorded either from Ireland itself or
from its offshore monastic communities, such as Iona,
and are accurate in their chronological and observa-
tional details. These observations and recordings of
astronomical and atmospheric phenomena in Irish
monasteries must be considered as evidence of scien-
tific enquiry, even if they ultimately served the escha-
tological purpose of looking for the “signs of Dooms-
day.” They show that the Irish had a deep interest in
the observation of natural phenomena and of the mea-
surement of the passage of time, and were capable of
doing so with considerable accuracy. Their astronom-
ical observations are therefore part of the same intel-
lectual phenomena that engendered their study of the
computus.
One of the earliest astronomical treatises penned by
an Irishman is that by Dungal of Pavia (d.
c.
830),
“instructor in the imperial court,”
magister palatinus
,
under Charlemagne and his son Louis. In 811 he wrote
a letter to Charlemagne, giving an account of a double
solar eclipse in the previous year. It is based mainly
upon the astronomical system of Macrobius and shows
Dungal to have possessed a rich learning in the Liberal
Arts and astronomy. He complains of the lack of cer-
tain works of classical astronomy that would have
helped him to answer the question more fully.
Cosmology
Pseudo-Isidore,
De ordine creaturarum
, a cosmological-
theological treatise on the structure and order of
divine creation, was written toward the end of the
seventh century. It used the
De mirabilibus
and other
Hiberno-Latin material. It has some striking cosmo-
logical theories and was one of the earliest texts to
expound the medieval doctrine of Purgatory in some
detail. Many of the problems connected with the sources
of this text remain unsolved. Later Irish Scriptural
commentaries on the Hexameron, the six days of cre-
ation, have some cosmological material, but most of
it is derived from the Fathers.
The greatest Irish thinker by far was John Scottus,
author of the massive
Periphyseon
(
De natura rerum
),
a complete system of cosmology, dealing with the
fourfold nature of God and creation, set in the form of
a dialog between master and pupil. It is the most com-
plete synthesis of medieval cosmology, and its pro-
found philosophical analysis of being and creation is
a tour-de-force unequalled in early medieval Europe.
An Irish origin has been claimed for Honorius of
Regensburg (
fl.
ante 1156), one of the most enigmatic
and prolific authors of the Middle Ages, wrote a num-
ber of works of cosmology and natural science, the
Clauis physicae
and
Imago Mundi. He disseminated
the theology and cosmology of Anselm and Johannes
Scottus in Germany before anyone else. His admission
into the canon of Hiberno-Latin literature would make
a considerable addition to the corpus of scientific work
by the Irish.
Geography
Dícuil (
c.
760-post 825), Irish scholar-exile at the
courts of Charlemagne and Louis the Pious and an
important author of several works on geography, com-
putus, grammar, and astronomy. The only details
known of his life are what can be garnered from inci-
dental references in his works. He was teacher at the
Palace School of Louis the Pious in about 815. His
first work,
Liber de astronomia
, is a verse-computus
written between 814–816 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. In
the same year he also wrote two other works, of which
the most important is his treatise on geography,
Liber
de mensura orbis terrae. Dícuil used a wide range of
sources for this treatise, some of them 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
. Among his other sources are Pliny, Solinus, and
Isidore of Seville. He had spent some time in the
islands north of Britain and Ireland, and had made a
note of their size and location. Dícuil seems to have
acquired his geographical knowledge of the islands
around Britain from some time spent as a monk on
Iona,
and he is a witness to the settlement in the eighth
century by Irishmen of the northernmost islands of
Britain and of Iceland. His descriptions of Egypt and