EsposiTO — Astro)toi)ucaI Treatise by the Irish 3Ionk Dicuil. 379 



sun and moon, the lunar cycle of nineteen years, the cycles of the 

 stars, and also the length of the solar and lunar years, are discussed. 

 At the beginning of the second book there is an account of the distances 

 between heaven and earth, and between the seven planets, where 

 some curious figures are given, though we are not told how these 

 numbers were arrived at. 



At the end of the last book there are some curious speculations 

 about the existence of a south polar star, and about the revolutions of 

 the planets. Here Dicuil shows that critical spirit, so rare in the 

 ninth century, which has excited the surprise and admiration of the 

 commentators of his geographical tract. Thus in explaining the 

 apparent motion of the sun and stars according to the theory then 

 adopted, he notices its unsatisfactory nature, and remarks that if 

 anyone would give him a better solution of the problem, he would 

 gladly adopt it. In another place he unfortunately omits to discuss 

 the influence of the moon on the tides, because, as he remarks, he 

 Avas then living far away from the sea, and would leave that matter 

 to those dwelling on the coast. 



Among the most remarkable things in the treatise are the sets 

 of sixteen-syllable rhyming couplets at the end of the first book, which 

 attracted the special attention of the German scholar Diimmler, the 

 discoverer of the work. Students of medieval Latinity — a subject 

 now-a-days of such importance that chairs of it have been established 

 at several German Universities, notably at Berlin, Gottingen, and 

 Munich — will find these verses, and also the discussion on metre and 

 how to write certain kinds of poetry, highly interesting. To the 

 historian of astronomy the treatise is all the more valuable from the 

 fact that we have very few medieval works on astronomy, written in 

 western Europe, and because it gives a succinct account of practically 

 all that was known on the subject in the ninth century. Most of 

 Dicuil' s information seems to be derived from his own personal 

 knowledge of the calculations employed by the Churches of Ireland, 

 England, and France in regulating the Calendar for the observance of 

 the various religious festivals. It is possible that he also got some 

 information from such works as the "Cursus Paschalis" of Victorius of 

 Aquitaine, recently published by Mommsen in his Chronica Minora. 



In conclusion, I may say that the whole work is full of interesting 

 and curious information, and it is certainly surprising that it has 

 never yet been published. It is important not only to the historian 

 of medieval science and to the student of medieval Latinity, but also 

 as a monument of Irish learning in the ninth century. 



