Among the weird legends of the Irish peasantry is found a class of stories peculiar both in the nature of the subject and in the character of the tradition. From the dawn of history, and even before, the island has been crowded with inhabitants, and as the centres of population changed, towns and cities were deserted and fell into ruins. Although no longer inhabited, their sites are by no means unknown or forgotten, but in many localities where now appear only irregular heaps of earth and stones to which the archæologist sometimes finds difficulty in attributing an artificial origin there linger among the common people tales of the city that once stood on the spot; of its walls, its castles, its palaces, its temples, and the pompous worship of the deities there adored. Just as, in Palestine, the identification of Bible localities has, m many instances, been made complete by the preservation among the Bedouins of the Scriptural names, so, in Ireland, the cities of pagan times are now being located through the traditions of the humble tillers of the soil, who transmit from father to son the place-names handed down for untold generations. Instances are so abundant as to defy enumeration, but a most notable one is Tara, the greatest as it was the holiest city of pagan Ireland. Now it is a group of irregular mounds that the casual observer would readily mistake for natural hills, but for ages the name clung to the place until at last the attention of antiquaries was attracted, interest was roused, investigation made, excavation begun, and the site of Tara made a certainty. Not all ancient Irish cities, however, escaped the hand of time as well as Tara, for there are geological indications of great natural convulsions in the island at a date comparatively recent, and not a few of the Irish lakes, whose name is legion, were formed by depression or upheaval, almost within the period of written history. A fertile valley traversed by a stream, a populous city by the little river, an earthquake-upheaval lower down the watercourse, closing the exit from the valley, a rising and spreading of the water, an exodus of the inhabitants, such has undoubtedly been the history of Lough Derg and Lough Ree, which are but reservoirs in the course of the River Shannon, while the upper and lower Erne lakes are likewise simply expansions of the river Erne. Lough Neag had a similar origin, the same being also true of Loughs Allen and Key. The Killarney Lakes give indisputable evidence of the manner in which they were formed, being enlargements of the Laune, and Loughs Carra and Mask, in Mayo, are believed to have a subterranean outlet to Lough Carrib, the neighborhood of all three testifying in the strongest possible manner to the sudden closing of the natural outlet for the contributing streams.