Before we leave the Roman period, we may remark that the manufacture of bricks and tiles must then have been known in England, because it was practised in such perfection by our conquerors during their occupation, as is evident in the numerous remains of their buildings.[23] It has, however, been asserted that up to the reign of Elizabeth, the houses of the gentry throughout England were built entirely of timber; whereas, of the mansions of earlier date than that reign, which remain entire or in part to this day, three-fourths, at least, are built of stone or brick. The latter material is stated by Bagford and others to have been first introduced in the reign of Henry VII. Yet, Endure Palace, in Oxfordshire, erected by William De la Pole, and Hurstmonceux Castle, in Sussex, both of which are of brick, are attributed to the reign of Henry VI. Oxburgh Hall, in Norfolk, was erected in the reign of Edward IV. Leland mentions the walls of Hungerford, as early as the reign of Richard II., being of that material; and Stow records Ralph Stratford, Bishop of London, inclosing the burial-ground of Charter-house, for those that died of the plague in 1348, with a wall of brick. That roofing-tiles were in use before the time of Richard I. is proved by the order made in the first years of that reign, Henry Fitzalwayne being Mayor of London, that the houses of that city should be covered with "brent tyle," instead of "strawe," or reeds. The ancient name for bricks appears to have been wall-tiles, to distinguish them from floor-tiles, used for paving. William the Conqueror lost no time in erecting strong castles in all the principal towns in the kingdom, as at Lincoln, Norwich, Rochester, &c. for the double purpose of strengthening the towns, and keeping the citizens in awe. The Conqueror's followers, among whom he parcelled out the lands of the English, imitated their master's example by building castles on their estates; and so rapidly did they increase, that in the reign of Stephen, or within a century after the arrival of the Conqueror, there are said to have been 1115 castles completed in England alone. One of the earliest was Conisborough Castle, built by William, the first Earl of Warren, about six miles west of Doncaster: the remains, as far as can be traced, extend about 700 feet in circumference; but the chief object is a noble round tower, strengthened by six massive square buttresses, running from the base to the summit. The extreme thickness of the walls is 15 feet; of each buttress 23 feet; and the entrance is 24 feet from the ground, up a flight of steps. In the centre of the first floor is a round hole, which is the only entrance to a lower apartment, or dungeon. This Castle is chosen by Sir Walter Scott for one of the principal scenes of his romance of _Ivanhoe_.