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XY. 



AN TJKPUBLISHED ASTRONOMICAL TREATISE BY THE 

 IRISH MONK DICUIL. 



Edited, with an iNTRODocTioif, by MARIO ESPOSITO. 

 Plate XXII. 



Read April 22. Ordered for Publication April 2i. Publislied August 6, 1907. 



Note. 



Very little is known about the Irish monk Dicuil. He wrote a short 

 geographical tract in the year 825 a.d., which has been published 

 twice in Erance and once in Germany, and is of considerable 

 importance, as it contains a record of the discovery of Iceland by 

 Irish monks at least sixty-five years before the arrival of the 

 Scandinavians in that island. The existence of an unpublished 

 astronomical work by the same author was pointed out for the first 

 time in 1879 by a German scholar, Ernest Diimmler, who discovered 

 it in a ninth-century irs., in the public library of Yalenciennes in 

 Erance. The ms. is a beautifully written one, with illuminations, and 

 was obtained from the ancient abbey of St. Amand in Elanders. It 

 was brought to the Yalenciennes library at the time of the Erench 

 Revolution. This treatise, of which I have prepared a text-edition, 

 was incorrectly attributed to Alcuin by the authors of the catalogue 

 of the Yalenciennes library ; but the author has given us his own name 

 in several passages. It is divided into four books, and was written, as 

 Dicnil himself tells ns, in the years 814-816 a.d., when he was 

 teaching in one of the schools of the King of the Franks, Louis le 

 Debonnaire, to whom the work is dedicated. 



The four books are written in Latin in a peculiar mixture of prose 

 and verse, and treat in the main of astronomical matters. Incidentally 

 grammatical and metrical questions are touched upon. 



The only authors quoted by name are Pythagoras and the 

 grammarian Donatus. Among other things, the treatise contains 

 rules for finding what month it is, counting from April, and what 

 day of the month, what the moon's age is, and what days Easter 

 and the beginning of Lent fall upon. The great cycles of the 



