Following up the ancient testimony, we find that Cairbre Nia Fear, the king of Tara in Cú Chulainn's time, was brother to Fionn File, the king of Dinn Riogh. Both were Leinstermen, Lagenians. Turning to the genealogies we find that the descent of all the Leinster kings in Christian times is traced from Fionn File. Tara therefore was the capital or royal seat of a Leinster kingdom, and that kingdom was one of the Great Fifths. If we look up Father Hogan's Onomasticon, we shall see that this fact was otherwise clearly recognised. The kingdom of which Tara was the capital was named in ancient writings by the name "Cairbre's Fifth," Cóiced Coirpri. Further we find that in many old documents the former existence of two Fifths belonging to the Laighin, or ruling folk of Leinster, is definitely recognised. One of these divisions is called Cúigeadh Laighean Tuadh-Gabhair and the other Cúigeadh Laighean Deas-Gabhair. These names mean that one of the Fifths lay to the north and the other to the south of a place or district called Gabhair. There were a number of places so named in various parts of Ireland, several of them in ancient Leinster. The word _gabhair_ was evidently a topographical term having a definite meaning indicating some physical feature of the country, but I have not found it defined in any dictionary or glossary. Examining the various instances of its use in place-names and the conformation of the localities so named, I have come to the conclusion that _gabhair_ most probably denoted a low broad ridge between two river valleys. There were two localities so named in the middle of Leinster. One was called Gabhair Life, with reference to the river Liffey. In the first poem of _Duanaire Finn_ it is mentioned as the place where dwelt the maiden Life from whom the river, we are told, took its name: "In Gabhair between two mountains, there the modest maid abode." This probably refers to the district of Donard in Co. Wicklow, between the waters of the Liffey and the Slaney. The two valleys are separated by a low watershed, and bounded on their outer sides by mountainous country. Westward from this, in the south of County Kildare, is a district which was anciently called Gabhair Laighean. This means Gabhair of the Lagenians, and the name suggests that it was the distinctive boundary between the two Fifths of the Lagenians. It is situated between the valleys of the Barrow, the Liffey and the Slaney, and may be regarded as the westward extension of Gabhair Life. Further evidence on the point is supplied by two glosses in the Book of Rights. One of these says that Laighin Deas-Gabhair is Ui Ceinnsealaigh, the other says it is Osraighe. I think we may take both together and regard the southern Fifth of Leinster as comprising both territories, which are represented by the dioceses of Ferns and Ossory. If O'Donovan is right in identifying Dinn Riogh with a site near Leighlin Bridge, on the bank of the