The materials with which castles were built varied according to the places of their erection; but the manner of building seems to have been pretty uniform. The outsides of the walls generally consisted of stones near at hand; the insides were filled up with fragments of stone, or sometimes chalk, and a large supply of fluid mortar. When the Normans found the remains of an ancient building on a site which suited them, they often added their out-work, thus having a mixed piece of architecture of a Norman and Saxon Order, with, not unfrequently, a quantity of Roman bricks. According to Camden, who gives an account of the taking of Bedford Castle, in his Britannia:—“The castle,” he says, “was taken by four assaults. In the first was taken the Barbican; in the second the outer bail (Ballium); at the third attack, the wall by the old tower was thrown down by the miners, where, with great danger, they possessed themselves of the inner bail through a chink; at the fourth assault, the miners set fire to the tower, so that the smoke burst out, and the tower itself was cloven to that degree as to show visibly some broad chinks; whereupon the enemy surrendered.” Castles in process of time, soon became of little use as fortresses; the change in the art of war, brought about by the invention of gunpowder, the influence of our navy, and the abolishment of the feudal system, all tended to diminish the importance of these ancient safeguards; and, with the progress of civilization and national improvement, we trace the gradual change in the construction of castles, till, by the admission of light and air, and some degree of ornament, the harsh and gloomy features of the massive Norman pile became softened down into the refined and comfortable aspect of the castellated house in the reign of Henry VIII. and Elizabeth. In the reign of Charles I., however, shortly before the civil war, and probably with the prospects of the awful events which followed in view, a commission was appointed to inquire into the state of the ancient castles. Many of these, during the subsequent troubles, were garrisoned and defended. Not a few were afterwards destroyed by order of the parliament, and others were left to the ravages of time and the weather. Some of these monuments of barbaric grandeur have been torn down for the sake of the materials, or for the purpose of building on the same site. Although a view of the generality of these rugged fortresses—destined chiefly for the purposes of war or defence—suggests to the imagination, dungeons, chains, and a painful assemblage of horrors, yet some of them were often the scenes of magnificence and hospitality, where, in the days of chivalry, the wandering Knight or distressed Princess found honourable reception, the holy Palmer repose for his wearied limbs, and the poor and helpless men daily bread.