There is a curious geographical poem[274] forming a sort of text-book on general geography which was used in the school of Ros-Ailithir in Cork of which the author MacCosse was Principal (Fer-gleighinn). This poem contained practically all that was then known of the principal countries of the world. It was written about the beginning of the tenth century. The tenth century map of the world drawn in England for an Anglo-Saxon is supposed to have been the work of an Irish artist.[275] Although inaccurate in many particulars this map is historically interesting as showing the state of geographical knowledge at this time. In teaching Greek the Irish monks used the _Nermeneumata_ of the Pseudo-Dositheus, the work of Macrobius _De Differentiis et Societatibus Graeci Latinique Verbi_, Latin glosses and interlinear versions.[276] With regard to the Pseudo-Dositheus and the book of Macrobius, Traube believes that were it not for the fact that these books were used by the Irish in teaching Greek both would have been lost to the afterworld. Mrs. Concannon conjectures that the earliest teachers of Latin brought with them to Ireland the third century _Disticha Catonis_ and used them as materials for teaching as well as for moral instruction.[277] The many copies of Priscian with numerous glosses thereon would suggest that this work was extensively used in Irish monastic schools. Traube has shown conclusively that the St. Gall copy of Priscian was written by some friends of Sedulius (of Liège) and supposes it was copied in some Irish monastery about the beginning of the ninth century and brought by Irishmen to the Continent.[278] Indeed, the glosses everywhere furnish objective proofs that the Irish monks were skilled practical teachers as well as accomplished classical scholars. In all these interlinear and marginal notes so abundant in the MSS. of the Old Irish period (prior to 900 A.D.) we see clear evidence of preparation for the work of teaching.