Nearly all the fortresses of this class were erected during the period that elapsed between the reign of the Conqueror and that of Edward the Third. The Castle of Rochester appears to have been erected soon after the decisive battle of Hastings; and in tracing its history and that of its founder, we shall adhere to the general opinion, so far as that may be found to harmonise with historical documents. Castles built on the Norman model varied according to the natural shape of the ground selected for their erection. The military baron, following the example of the Roman general, selected that position to which nature had given the best means of security, which provided against sudden approach or surprise, and in cases of extremity, offered some facilities for escape, of which various instances are recorded in history. The sites chosen were generally on capes or promontories overlooking the sea; on high banks protected by a river, or on isolated hills, where connecting valleys, by forming a natural fosse, would interpose a chasm between the besiegers and the besieged. These natural positions were readily taken advantage of by the warlike baron; while the difficulty of access could be increased by artificial means, such as damming up the stream which flowed through the ravine, and thus transforming it into a temporary lake. The situation of Rochester Castle is partly an example of this kind: the high ground on which it stands, and its immediate access to the river, were natural recommendations not to be lost sight of; and which the founder took every opportunity of turning to the best account. In castle-building the general maxim was-- “Where the land o’erlooks the flood, Steep with rocks and fringed with wood; Where, throughout the circling year, Wells the fountain fresh and clear; Scoop the dungeon, rear the wall, Pile on high the feudal hall.” We shall now quote one or more authorities respecting the Castle of Rochester. “Neere unto the church,” says Camden, “there standeth, over the river, an olde Castle fortified both by art and situation, which, as the report goeth, Odo, Bishop of Bayeux and Earle of Kent, built; but it was no doubt King William the First that built it; for, in Domesday Book we reade thus: ‘The Bishop of Roucester holdeth in Elesford for exchange of the land on which the castle is seated.’ Yet certain it is that Bishop Odo, when his hope descended of a doubtful change of the state, held this against King William Rufus; all which time there passed a proclamation through England, that whosoever would not be reputed a ‘niding,’ should repair to the recovery of Rochester Castle. Whereupon, the youth, fearing that name as most reproachful and opprobrious in that age, swarmed thither in such numbers, that Odo was enforced to yield the place, lose his dignity, and abjure the realme.”