centre of the walls, and by subterraneous passages made under the fosse, as mentioned in the notice of Eltham. In advance of the ditch or moat, was the barbican, or outer defence, with a watch-tower that communicated with the interior by means of a drawbridge across the moat, which opened inwards, so as to be under the control [Illustration] of the sentinel or guard. The entrance to the ballium, or outer court, was secured by gates, with a ponderous grating or portcullis, which was raised or lowered by means of those iron chains and pulleys which are still used in some of our military fortresses, and are always met with in the fortified cities of the Netherlands. The walls were further protected by towers and battlements, from which, as well as through the numerous loopholes by which they were perforated, arrows and other missiles could be discharged with deadly effect; while through the apertures of the machicolation above, “Sudden, on the assailants’ head, Blocks of stone and molten lead, O’er the foe descending--gushing, Scorching as they fell, or crushing Helmèd warriors in their fall, Guarded each embattled wall.” The outer walls were generally from six to ten feet thick; those of Rochester Castle are seven[106]; while the walls of the keep, to which all looked for retreat under desperate circumstances, were often fifteen feet in thickness, and contained in their centre many secret closets, passages, and recesses, to which none but the castellan and his family had access. In the castle of Glamis[107] there is a secret chamber, the key of which is transmitted from father to son, and never known to more than the “seigneur actuel,” and some trustworthy official. Before the invention of artillery, one of these strongholds, such as we have described, might have been considered impregnable; and when taken, the surrender was generally in consequence of famine, revolt or cowardice on the part of the garrison, or of stratagem on that of the besiegers.