CASTLE, a building constructed for the purpose of repelling attack. The castella left by the Romans in Great Britain and elsewhere were constructed on the general model of their stationary encampments (castra stativa), and though they may have suggested the castles of the Middle Ages, they differed from them in being designed for military purposes only, and not also as places of permanent residence. The Norman cas tles were generally surrounded by a moat or ditch; and in order that the ditch might be readily filled with water the site chosen was usually either on the banks of a river or on a peninsula run ning into a lake; on the inner side of the ditch mounds were constructed, which were surmounted with walls and towers, both of which, but particularly the latter, were supplied with battle ments and bastions. The entrance-gates were also protected by towers, which were usually of great strength. The communication was by a bridge, some times of stone, but usually of wood, which was made to draw up and down; and the entrance, in addition to thick folding-doors, was protected by a port cullis, which was dropped down through grooves in the masonry at the sides. The
gate-way, in the castles of the larger sort, was further defended by a barba can. On passing the external wall one entered the bailey, which sometimes con sisted of several courts, and contained the barracks, magazines, well, a chapel, and sometimes even a monastery. The keep was a species of internal castle, more strongly defended than any other portion of the fortress, and placed in the most advantageous position, so as to af ford a last chance to the garrison when driven from the external works. As the keep had the same design as the castle itself, it contained most of its appliances, even to a chapel, when large and com plete. The keep was also called the dungeon or donjon.