To the researches of Mr. Close we are indebted for our knowledge of one of the Latin texts which is the source of the major part of the work in hand.
Two-thirds of the tract are part paraphrase and part translation according to Mr. Close, of a Latin version of an Arabic treatise by Messahalah or Mascha Allah, a Jewish astronomer of Alexandria, who flourished shortly before 800 A.D. This work was translated into Latin by Gerard of Sabionetta, near Cremona, in the thirteenth century, and, edited by J. Stabius, was printed at Nuremburg in 1504 under the title De Scientia Motus Orbis. A transcript of this, obtained by Mr. Close from a copy in the British Museum, is in the Academy Library.
My translation of the Irish text had already been made when this was found, but it was not too late to make use of the help it furnished in the rendering of certain passages evidently misunderstood by the Irish translator. This transcript is now numbered 3. B. 32. Gerard's work was again edited by Joachim Heller, under the title De Elementis et Orbibus Celestibus,
The Irish text cannot be said to be a literal translation of Stabius. It is rather an adaptation. In parts the rendering is indeed literal, but there is scarcely a chapter where there is not either more or less matter than in the corresponding Latin version. These additions, if they can be so designated, are not mere interpolations in so far as they are not detrimental to the sense, nor do they differ in language or style from the passages for which we have corresponding Latin. In the same way the omissions do not leave gaps in the arguments, and it is quite probable that this edition of Stabius is not the actual original of the Irish rendering, and the Irish translator may have had some other edition of Gerard of Sabionetta's work before him.
The portion of the text not in the Latin of Stabius consists of the introductory remarks down to the table of contents and chapters 7, 8, 9, 10, 11, 12, 14, 15, 17, 35, 36, 37 (34, 35, 36 according to numbering of the English translation from which Mr. Close worked). Of the original of these chapters nothing is known. They are evidently drawn from another Latin text or texts, and some of them are apparently of much later date than Messahalah's
Mr. Close remarks that in chapter 36 (35) the habitable regions of the earth are carried further north than they would have been in Messahalah's time, and points out some statements in these chapters contradictory to the teachings of Messahalah. It is noteworthy that the interesting chapters on geology (8), that on mineral springs (9), that on volcanoes (10), on the tides (11), on the Nile (12), the seven habitable regions (36) are non-Messahalic and non-astronomical, so it would seem that the source from which these chapters were taken was cosmographical rather than purely astronomical.
The Messahalic astronomy is in the main that of Ptolemy; but I do not propose to discuss the subject here, nor the treatment it has received at the hands of the Irish translator, as Mr. Close deals with it in much detail in his article, to which I again refer my readers.
There is, however, just one error in the same article due to the entire omission of two words in the text which are at first sight unintelligible owing to a mistake on the part of the scribe. Mr. Close was greatly surprised that in chapter 35 (34) the ratio of the circumference of a circle to its diameter is taken as 3 to 1, Archimedes having shown long before even Messahalah's time, that the ratio is between 3 10/70 and 3 10/71, and Alfergani, a contemporary of Messahalah, made it equivalent to 3 1/7.
The text here contains a curious error which can be easily corrected. It runs tri mile & feth. It is evident that the scribe intended to write s instead of f and, if we read tri mile & seachtmadh, we get the fraction correctly.