Though the castles of Ireland, in point of architectural magnificence, are not to be compared with many of the more important structures of a similar character in England, they are frequently of very considerable extent. Placed as they often are upon the summit of a lofty and precipitous rock, the base of which is usually washed by the waters of a river or lake, or by the sea, encompassed with walls and towers pierced with shot-holes, and only to be approached through well-defended gateways, they must, before the introduction of artillery, have been generally considered impregnable. Several of the early keeps are circular; but they usually consist of a massive quadrangular tower with smaller towers at the angles. The internal arrangements are similar in character to those seen in the military structures of the same period in England and elsewhere. The outworks and other appendages to the majority of the most remarkable castles in Ireland have been destroyed, not by the usual effects of time and neglect, but by gunpowder, as the enormous masses of masonry overthrown, and lying in confused heaps, sufficiently testify. The cannon of the Cromwellian army left most of the strongholds of the Irish and of the Anglo-Irish in ruins. Shortly after the Restoration the necessity for castles ceased; and, with some exceptions, the few that had escaped the violence of the, preceding period appear gradually to have been deserted and suffered to decay. * * * * * [Illustration: Malahide Castle, Co. Dublin.]