places, but by the want of organisation for their defence. But whatever may have been the character of the defences in use in England before the arrival of the Normans, it is certain that from that period they underwent a considerable and probably a rapid change, though scarcely so rapid as has been supposed. The Normans, who had so long, in common with the English (probably by reason of their common ancestry), employed the moated and palisaded mound, proceeded to carry out in England the important improvements they had already commenced in Normandy. William’s chief object, having conquered, was to secure his conquest; and his first care, on obtaining possession of each division of the kingdom or each capital city or town, was to regard it from a military point of view, and to order the construction of such strong places as might be necessary for the holding of it. How completely, in so doing, he trod in the footsteps of those who had gone before, is shown by what he found and what he did towards the covering of London and the maintaining of his communication with the sea. Thus he found and reinforced castles at Chichester, Arundel, Bramber, Lewes, Hastings, and Dover. On his road he found and strengthened Canterbury, Tonbridge, Rochester, and Ryegate. In London he founded the Tower, an entirely new work; but for the defence of the basin of the Thames he trusted to the ancient sites of Guildford and Farnham, possibly Reading, and certainly Wallingford and Berkhampstede. And so all over the kingdom, such strongholds as were central, in good military positions, or of unusual strength, or were placed in the ancient demesne lands of the Crown, were taken possession of or reconstructed for the sovereign; but every baron or great tenant in chief was permitted,—and, indeed, at first expected, and was no doubt sufficiently ready,—to construct castles for the security of the lands allotted to him, which in the vast majority of instances meant to remodel the defences of his English predecessors. This was under the pressure of circumstances; for William seems always to have been awake to the danger of uniting extensive hereditary jurisdictions, and even from the first to have contemplated governing the counties through the intervention of _vice-comites_, or sheriffs, who were appointed and could be displaced at pleasure. But this policy was at first, in certain districts, necessarily postponed; though even then William made it to be understood that the chief castles of the realm, by whomsoever built, were royal castles; and their actual acquisition was always an important part of the policy of both him and his successors so long as castles were of consequence. Thus Windsor, Cambridge, Exeter, Corfe, Wareham, Winchester, Porchester, Southampton, Carisbrooke, Canterbury, Dover, Lincoln, Rockingham, Nottingham, Stafford, Guildford, Warwick, Marlborough, and York were royal castles from the commencement.