Wallingford, Gloucester, Bristol, Oxford, Tutbury, Worcester, though built by subjects, were not the less claimed and officered by the Crown. Even Durham, though held by the bishops, and Leicester, Lincoln, and Huntingdon, by the lords of those earldoms, were from time to time in the hands of the Crown, whose rights over them were of a far more direct character than those it claimed to exercise over the lands and other feudal possessions of the same lords. Arundel, Shrewsbury, Montgomery, Bridgenorth, and some less important fortresses, fell to the Crown on the overthrow of the house of Talvas; and with this event a number of castles on the Welsh border, built by tenants of Earl Roger, became fiefs _in capite_, dependent directly upon the Crown. Besides these, there are on record in England about forty or fifty castles built by local barons, which, when it suited the Crown, were taken in hand and repaired and garrisoned at its charge. Of nearly all the castles on record, as existing in the reigns of the Conqueror and his sons, the sites are well known; and of very many, fragments of the masonry remain. What is very remarkable is, that of this masonry there is but little which can be referred to the reign of either the Conqueror or William Rufus,—that is, to the eleventh century. Of that period are certainly London and Malling, Guildford, Bramber, Carlisle, the gate-house of Exeter, the lower story of Chepstow, the keeps of Chester, Goderich, Walden, Wolvesey, Colchester, and Newcastle, though this last looks later than its recorded date. Newcastle was probably on the site of an earlier castle; at least, the entry in the Hundred Rolls (ii., 119),—“Juratores dicunt quod Vicecomes ... fecit quandam inquisitionem ... super motam castri predictæ villæ,”—looks like it. There is some reason to regard the keep at Malling as the earliest Norman military building now extant in England, and as the work of Gundulf, the architect of the Tower keep. The North or Gundulf’s tower at Rochester Cathedral is by the same great builder, and possibly was intended as a military building: if so, it may rank with Malling. Probably there is more of this early masonry; but not much. Dover, Rochester, Porchester, and Hedingham, among our finest examples, are certainly later. Part of Durham Castle is, no doubt, of the age of the Conqueror; but the shell keep has been rebuilt, and it is doubtful whether the original work was of the age of the early Norman chapel and hall attached to it. Speaking generally, those castles in England which belong to what is called the Norman period are too late to be the work of the Conqueror or his personal followers, and too early to allow of any preceding work in Norman masonry (usually sound and solid), having been constructed and swept away. What is the solution of this difficulty? Of what character and material were the great majority of the castles which William ordered to be constructed?