Thus we read that Armagh, the center of St. Patrick's work, and the chief home of learning, was thrice plundered in 830, the raiders sailing up Carlingford Lough and then making a dash of some fifteen miles across the undulating country separating them from the city of churches. This is the first time they ventured out of sight of their boats. Two years later they plundered Clondalkin, nine miles inland from the Dublin coast, where the Round Tower still marks the site of the old church and school. To the growing frequency of these raids, it would seem, the building of Round Towers is to be attributed; they were at once belfries and places of refuge. We find, therefore, that the door is almost always many feet above the ground, being reached by a ladder afterwards drawn up by those inside. The number of these Round Towers all over the country, and the perfect preservation of many of them, show how universal this precaution was, and how effective were the refugees thus provided. It is instructive to read under this same year, 832, that "a great number of the family of Clonmacnoise were slain by Feidlimid king of Cashel, all their land being burned by him up to the door of the church." Thus the progress of tribal struggle was uninterrupted by the Gentile raids. Four years later, a fleet of sixty Norse fighting galleys sailed up the Boyne. Sixty long ships entered the Liffey in the same year, and a year later they captured the fortress of the Ford of the Hurdles, At-Cliat,--the old name of Dublin. Three years later we find the king of Munster plundering Meath and West Meath, showing that no sense of common danger disturbed the native kings. This strengthens the view we have already taken: that the attacks of the Norse sea-kings were only an interlude in the incessant contests between the tribes of province and province; contests perfectly natural and normal to the development of the land, and through which every country has at some period passed. [Illustration: Round Tower, Antrim.] It would seem that the Northmen who captured the Ford of the Hurdles departed from their former usage. Fortifying themselves, or strengthening the existent fortress, they determined to pass the winter in Ireland, instead of returning, as they had always done up to this time, before the autumn storms made dangerous the navigation of the wild northern seas. Their presence in this fort gave the native powers a center upon which to concentrate their attack, and as a result the year 846 was marked by a signal victory over the Northmen, twelve hundred of those at At-Cliat being slain. Four other successful contests with the raiders are recorded for the same year, and we can thoroughly trust the Annalists who, up to this time, have so faithfully recorded the disasters of their own race.