410
HISTORY OF ENGINEERING.
Cook I.
a barbican or watch tower, communicating by means of hidden passages witli the strongtower on the mound.
The Normans constructed a castle in every lordship, and w'hen material was noteasily obtained, they frequently imported stone from Caen for casing the walls, and for theornamental portions of the interior, the internal and external facing being filled in with aconcrete composed of pebbles, flint, or chalk, run with fluid mortar. The great thicknessgiven to the walls enabled their engineers to practise within them staircases, guard-rooms,chapels, and every kind of accessory apartment that the inhabitants could require during asiege. The keeps of London and Dover, Hedingham, Norwich, Porchcster, Scarborough,Colchester, and others, though dismantled, convey to us an idea of the great discernmentand skill of those under whose direction they were raised.
At the entrance story of Coningsburgh, the internal diameter is 22 feet 1 inch, thethickness of the walls where the buttresses are attached the same. Between the buttressesit is only 13 feet 7 inches. The entire diameter, measured through to the flat outer faceof the buttresses, is three times that of the interior. The six buttresses are half hexagons,and on this floor solid throughout; each of their sides internally measure 8 feet 10 inches,the distance apart is 12 feet 4 inches, and from angle to angle in a straight line 26 feet.
The entrance, 24 feet from the ground, is approached by a lofty flight of steps, and isonly 4 feet 4 inches in width; after passing through half the length of this passage, on theright, in the middle of the wall, is a stone staircase conducting to the apartment above, towhich the only light admitted is from the aperture shown between the buttresses.
In the centre of the floor of this apartment is a circular hole communicating with a lowerapartment, at the bottom of which was probably the well that supplied the tenants of thekeep with water during a siege.
Some writers suppose that this keep was constructed by the Saxons, and that Williamthe Conqueror bestowed it upon the husband of his sister Gundred, but of this we have nodirect evidence: the castles of the Saxons were often entered as this was, by an aperture ata considerable height from the ground, either by ropes or a wooden ladder. The readeris referred to the “ Arclueologia ” for a description of a castle at Eynsford in Kent , by theauthor. The only entrance is at the top of the wall, and no one could have gained ad-mittance without being hauled up, or supplied with a wooden ladder.
The first story has a fireplace of a curious construction, perhaps the earliest example wecan produce of such a contrivance in England. Light is admitted over the entrance door-way by a double opening; and in one of the buttresses is a closet, entered through apassage 2 feet 6 inches in width.
A staircase in the thickness of the wall conducts to the floor above. The mantelof the fireplace is formed of nine stones, so cut as to hang on each other, and preserve alevel line below, show-ing all the properties ofa flat arch. Above thisarch runs a level mould-ing, on which the ma-sonry rests, bevelledover so as to gather theflue into the thicknessof the wall; the chimneyat Coningsburgh seemsto have been built upat the same time as thisportion of the keep; theopening is 7 feet 3 inches,and depth 18 inches;on each side is a triplecolumn, with capitalsand bases.
The thickness of thewalls at this story is13 feet 6 inches, andaround the interior facethe stone corbels thatcarried the timber floorstill remain.
The second story,
27 feet in diameter, ap-pears to have been en-tirely devoted to thebaron and his familv;
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L-ii
Fig. 110.