South of Denbigh, in Montgomeryshire, are the ruins of Montgomery Castle, long a frontier fortress of Wales, around which many hot contests have raged: a fragment of a tower and portions of the walls are all that remain. Powys Castle is at Welsh Pool, and is still preserved--a red sandstone structure on a rocky elevation in a spacious and well-wooded park; Sir Robert Smirke has restored it. THE MENAI STRAIT. Still journeying westward, we come to Caernarvonshire, and reach the remarkable estuary dividing the mainland from the island of Anglesea, and known as the Menai Strait. This narrow stream, with its steeply-sloping banks and winding shores, looks more like a river than a strait, and it everywhere discloses evidence of the residence of an almost pre-historic people in relics of nations that inhabited its banks before the invasion of the Romans. There are hill-forts, sepulchral mounds, pillars of stone, rude pottery, weapons of stone and bronze; and in that early day Mona itself, as Anglesea was called, was a sacred island. Here were fierce struggles between Roman and Briton, and Tacitus tells of the invasion of Mona by the Romans and the desperate conflicts that ensued as early as A.D. 60. The history of the strait is a story of almost unending war for centuries, and renowned castles bearing the scars of these conflicts keep watch and ward to this day. Beaumaris, Bangor, Caernarvon, and Conway castles still remain in partial ruin to remind us of the Welsh wars of centuries ago. On the Anglesea shore, at the northern entrance to the strait, is the picturesque ruin of Beaumaris Castle, built by Edward I. at a point where vessels could conveniently land. It stands on the lowlands, and a canal connects its ditch with the sea. It consists of a hexagonal line of outer defences surrounding an inner square. Round towers flanked the outer walls, and the chapel within is quite well preserved. It has not had much place in history, and the neighboring town is now a peaceful watering-place. [Illustration: THE MENAI STRAIT.] [Illustration: BEAUMARIS CASTLE.] [Illustration: BANGOR CATHEDRAL.]