The whole intricate system of Irish genealogy, jealously preserved from the very first, as all Irish literature goes to show,[4] played so important a part in Irish national history and in Irish social life, and is at the same time so intimately bound up with the people's traditions and literature, and throws so much light upon the past, that it will be well to try to get a grip of this curious and intricate subject, so important for all who would attempt to arrive at any knowledge of the life and feelings of the Irish and Scottish Gael, and upon which so much formerly depended in the history and alliances of both races. All Milesian families trace themselves, as I have said, to one or other of the three sons of Milesius, who were Eremon, Eber, and Ir, or to his uncle Ith, who landed in Ireland at any time between 1700 and 800 years before Christ according to Irish computation.[5] But while they all trace themselves back to this point, it is to be observed that long before they reach it, in each of the four branches, some place in the long row of ancestors is arrived at, some name occurs, in which all or most of the various genealogies meet, and upon which all the branch lines converge. Thus in the Eberian families it is found that they all spring from the three sons of Oilioll [Ul-yul] Olum, who according to all the annals lived in the second century--in this Oilioll all the Eberian families converge. Again all, or nearly all, the Irians trace themselves to either Conall Cearnach or Fergus Mac Roy, the great Red Branch champions who lived in the North shortly before the birth of Christ. The tribes of the Ithians, the least numerous and least important of the four, seem to meet in Mac Con, king of Ireland, who lived in the second century, and who is the hero of the saga called the Battle of Moy Mochruime, where Art, son of Conn of the Hundred Battles, was slain. In the line of Eremon only, the greatest of the four, do we find two pedigrees which meet at points _considerably antecedent_ to the birth of Christ, for the Dál Riada of Scotland join the same stem as the O'Neills as much as 390 years before Christ, and the O'Cavanaghs at a still more remote period, in the reign of Ugony Mór. But setting aside these two families we find that all the other great reigning houses, as the Mac Donnells of Antrim, Maguires of Fermanagh, O'Kellys of Connacht, and others, either meet in the third century in Cairbré of the Liffey, son of King Cormac mac Art, and grandson of Conn of the Hundred Battles; or else like the O'Neills of Tyrone, O'Donnells of Tirconnell, O'Dogherties of Inishowen, O'Conors of Connacht, O'Flaherties of Galway, they meet in a still later progenitor--the father of Niall of the Nine Hostages.