castles this outer ward contained a ditch, or even a large sheet of water, as at Ledes, Caerphilly, and Kenilworth, formed by damming back a local streamlet. In such cases the defence of the dam became a matter of prime consequence, and was specially provided for by stout walls along its length, and towers or gatehouses at either end. In these castles every part is intended for everyday use. No part is set apart only to be inhabited during a siege. The hall, chapel, and kitchen were habitually used, and constructed on a fitting scale. As Caerphilly is both the earliest and the most complete example in Britain of a concentric castle, it will be convenient briefly to point out its principal features. The position was selected to close a pass by which the Welsh were wont to issue from the hill country of Glamorgan into Monmouthshire, the way by the sea coast being barred by Cardiff and the castles of the vale. The spot selected lay between the Taff and the Rhymny, upon a gravel bank rising in a low marshy bottom, having mountainous, or at least very high ground to its north, south, and west. The central part of the bank was occupied by a rectangular enclosure, 70 yards by 53 yards, having at each angle a lofty drum tower, and in the centre of each end a broad and lofty gatehouse. On one side of this inner ward was the hall, 72 feet long by 33 feet wide, placed between the chapel and the private apartments, while the gatehouses also contained apartments second only to the hall in magnitude. This inner ward stood within a second and rather larger area, also rectangular, and 106 yards by 90 yards. This middle ward was provided with smaller gatehouses connected with those within, and was contained within a revetment and parapetted wall which descended 20 feet all round into water. Four parapetted bastions, corresponding to the interior towers, capped the four angles, and the side next the hall contained the kitchen and offices, and a water-gate opening from the hall by a broad passage with space for the stowage of boats.