We have glanced at the process by which one of our poet-historians endeavoured to transform popular tradition into a kind of history more acceptable to his own school. Christian learning brought into Ireland a double stream of history, derived from the Old Testament and from the Greek and Latin historians. The two streams had already been mingled in one by early Christian historians like Eusebius and Orosius. The works of these writers were well-known in early Christian Ireland. The Chronicle of Eusebius, a history of the ancient kingdoms of the world, written in parallel columns, a column to each kingdom, was known through the Latin translation by St. Jerome and its continuation by Prosper of Aquitaine in the fifth century. It became the basis of the writing of Irish history, and was continued in Ireland, with an Irish section added, down to the early years of the seventh century. By adopting this basis and model, the early Christian historians of Ireland brought themselves inevitably face to face with the task of linking and fitting the old Gaelic tradition to this existing framework of Biblical and Greco-Latin history. We cannot doubt that the Celts, like the Greeks, Persians, Egyptians, Northmen and other ancient peoples, had what is called a cosmogony of their own, an account of the beginning of the world. Cæsar tells us that the Druids expounded the nature of the gods and also of the material universe. This cosmogony could find no place in the new scheme, and it disappeared, leaving perhaps a few traces in the genealogies. In like manner, other parts of the popular tradition and native lore required to be transformed and recast to find a place in the accepted scheme of world history. That is why the Tuatha De Danann became mortals in the teaching of the learned while they remained and still remain immortal in the traditions that come down from heathen times. The native tradition had its own account of the origin of the Celtic people. That account, as we shall see, was not such as could be adopted into the Christian world-history received from Eusebius and St. Jerome. It was completely rejected by the Irish historians, as completely as modern Irish people reject the substituted account when they say that their ancestors were Celtic. To provide a theory of the origin of the Gaels more in keeping with the received world-history, a search was made through the Latin historical and geographical writings that were used in the Christian schools of Ireland and suitable discoveries were made. The most serviceable material for the purpose was found in the world-history of Orosius, a Spanish historian who wrote in Latin about the year 400. Quotations from Orosius by name and word for word show that his book was well-known in the Irish schools. It had the advantage of combining a geography of the world with a history of the world.