So great were their numbers at one time during the ninth century that we are told that it seemed as if the sea vomited them forth, and that there was hardly a harbour on the Irish coasts in which there was not a Danish or a Norwegian fleet. It has to be admitted that the Irish fought them with the most astonishing persistency and valour. In spite of the way the country was split into petty kingdoms, with chief kings, who were generally such only in name, the reception the Northmen got in Ireland was very different from that which they got in England. The Saxons often got rid of them by paying them to go away, but the Irish got rid of them only by the sword. Those who want to know what Ireland suffered from the raids of the Northmen should read the "Wars of the Gael and the Gaill." The book is generally believed to have been written by M'Liag, who was living when the battle of Clontarf was fought, and who was chief poet, or secretary, to Brian Boramha. Although the Northmen were allies of Leinster for a long time, they plundered Glendaloch in the years 833, 886, and 982. It was so near Dublin and so near the sea that their alliance with Leinster did not prevent them from raiding it. It was one of the rich ecclesiastical establishments in Ireland, and one of those most exposed to the incursions of the Northmen. Its round tower was, therefore, in all probability, one of the first that was erected. It is now generally believed by those most competent to form an opinion that the round towers of Ireland were erected as places of security against the Northmen, and that they were sometimes used as belfries. Their Irish name, _cloigtheach_, means a bell house and nothing else; but it is quite clear that, although they sometimes served as belfries, the primary object of their erection was to secure a place of safety for the treasures of the church or monastery, close to which they were invariably erected. Of the hundred and eight round towers which are known to have been erected in Ireland, and of which remains exist, every one of them is known to have been erected close to where a church or monastery stood. More than half of them are in ruins; of some only a few feet of the walls remain; and of some others the foundations only remain. It may seem hard for some, in these days of far-reaching projectiles to imagine how those slender towers, so chaste and beautiful in their construction, could serve as places of defence or security against the Danes. They could not have served as such if the Danes had come as conquerors to form permanent settlements, but as they were only raiders the towers were generally perfect defences against them. A dozen men shut into a round tower, the door of which was generally from ten to fourteen feet from the ground, could laugh at an army of Danes who had neither battering rams nor artillery of any kind. There was only one way by which a round tower could be taken or destroyed by men like the plundering hosts