Having regard to the state of the military art at that period, and to the cross and long bows, catapults, rams, scorpions, and moveable turrets that formed the weapons of attack, it would be difficult to improve upon these concentric works, either in general design or in detail of construction, or to show greater skill in flanking defences than appears at Corfe, Caerphilly, Conway, or Beaumaris, or in many other of the castles built by Henry and his son. This science, so successfully grafted upon the pure Norman works, was no doubt in some considerable measure derived from the East, where Coeur de Lion seems to have acquired the skill displayed in the construction of Chateau-Gailliard, and which, in the opinion of M. Le Duc, places him at the head of the military engineers of his day.

When, having crossed the Thames, the Conqueror marched in person to complete the investment of London, he found that ancient city resting upon the left bank of its river, protected on its landward side by a strong wall, with mural towers and an exterior ditch.

The enclosure, of about 370 acres, was in general figure a semicircle; the river forming the chord. The defences, commencing on the Thames at Blackfriars, upon the east bank of the Flete, swept in an irregular curve northward and eastward, by Ludgate, Aldersgate, Cripplegate, and the line of London Wall to where, trending eastward and southward, they took the line of Houndsditch, and appear to have abutted upon the Thames a little east of or below Billingsgate.

C

Upon the west the Flete formed a respectable natural defence, and upon the east the line took the crest of the high ground just where it begins to subside into the low lands long occupied by St. Katherine's Hospital, and now, more suitably, by the docks of that name. Towards the north the defence must have been wholly artificial, and is reputed to have been by a ditch which, in the later reign of King John, was deepened and made 204 feet broad, but which must have been a sufficient defence even at the time of the Conqueror. Ludgate, like the later Newgate, was placed in a re-entering angle of the wall, so that the road approaching it from the west ran for a short distance parallel to, and commanded by the ramparts. London, therefore,

"A læva muris, dextris in flumine tuta,"

resembled in plan and mode of entrance those large half-round Celtic earthworks sometimes found upon the banks of a water-course; nor does there appear to have been attached to or within it anything of the character of a prætorium or citadel.

It is related that before the Conqueror entered London he directed a fortress to be built which should command the city. This of course was a temporary camp, and it was probably while he was at Westminster, or in the camp at Barking, that he studied the ground and selected as the site of his future citadel a point upon the eastern flank of the city defences, displacing for that purpose, we are told, a part of the Roman wall, including the two towers next to the Thames.

William was crowned in 1066, and it was from Barking, immediately after the ceremony, that he directed the actual commencement of the works, which were no doubt a deep ditch and strong palisade only; for the keep, probably the earliest work in masonry, appears not to have been begun till twelve or fourteen years later. It is said to stand upon the site of the second Roman bulwark; but looking to the wellknown line of the city defences, it seems more probable that so massive a structure was placed on undisturbed ground, a little to the east and outside of both wall and ditch. Roman remains have been found within the precinct.

The new castle thus more than supplied the place of the removed works, for it could not only protect, but overawe the city, and, if necessary, cut off its trade and supplies by water.

Such was the origin of this grand old fortress, the chief and central part of which gives mass and character to the group, and has from its earliest times caused the whole to pass under the name of "The Tower."

The new fortress was supported by two other considerable works within the city, Baynard's Castle upon the Thames' strand, built about the same time by Baynard, the Castellan and standard-bearer of the city, and Montfitchet's Castle, near it, built by a knight of that name. Later kings had "Tower

Royal," in Vintry Ward, where Stephen lodged, and to which the mother of Richard II. fled from the

Tower in Wat Tyler's rebellion. built a strong place near Blackfriars.

Edward II. also

The Tower, though all save the keep is later, and most of it considerably later than the eleventh century, probably supplements the original design. The area enclosed and the strength of the walls and gates are in keeping with the dimensions and impregnable character of the keep; and the circumscribing ditch, though unusually broad and deep, was by no means too secure a defence against a turbulent and notoriously brave body of citizens.

The Tower, in its present form, is a fine example of a concentric castle, of mixed composition, but general harmony of design, and covering, with its circumscribing ditch, above twelve acres of ground.

Nearly in the centre, but now detached and alone, stands the keep, the oldest and most stable part of the fortress. Around it is the inner ward, in plan generally four-sided, but with a salient on the north front, and contained within a wall strengthened by a gatehouse and twelve mural towers.

Encircling this is the outer ward, following the same general plan, and contained within a wall rising from and forming the scarp of the ditch. Upon it are bold drum bastions, at the angles of the north front; and the south, or Thames front, is protected by five mural towers, of which one covers the land and one the water-gate, and two others are connected with. posterns.

The ditch, which completely girdles the fortress, is divided from the river by a narrow strip of land used as a wharf, but also ingeniously contrived to cut off the water of the ditch from the tidal stream.