334
HISTORY OF ENGINEERING.
Book I.
present slake or morass, consisted of several acres, where a hundred sail might be moored.From this gateway commences the wall, which secured the haven, and runs in a direct line,the water at high tide coming up to the gate. It is somewhat more than 8 feet thick, facedon each side with dressed stone; the parapet is guarded by a breast-wall and embrasure,now greatly decayed, 'There is a water gate in the wall, formed by a low pointed arch,above 24 feet in span, and 10 feet high, for the small craft to pass in and out of the haven,without removing the boom chains afterwards noted ; the gateway projects from the wallabout 18 inches; it has had flood gates, and also a watch tower, as we apprehend from theremains of the superstructure. From thence, at about the distance of seventeen paces, is asquare bastion about 8 feet in front; and nearly a hundred paces distant is another squarebastion, and from thence about seventy paces is a lofty round tower, remaining very perfect,save the parapet and embrasures; opposite to it, at the distance of 36 feet, stood anothertower, exactly similar in dimensions, as the fascia and foundations plainly show. Thiswas the grand entrance into the haven, and by the space between the towers one mayjudge of the size of those vessels which were moored therein, a thirty-gun ship being 32 feetwide.
This entrance was guarded by large boom chains, stretched from tower to tower, the re-mains of the hoops belonging to such chains being still visible in the walls of the tower.At ten paces distant are the foundations of a round bastion, near which is a modern gate,where, it is presumed, was formerly a small doorway, for the convenience of persons landingfrom boats ; at 24 paces distant the wall forms an angle ; this angle is defended by a halfmoon.
The entrance into the haven had the peculiar security that vessels coming from the seamust necessarily double the cape or point of the isthmus, and then proceed along the wholerange and stretch of the south wall, within reach of the engines and instruments of war,and pass the half moon which guarded the angle of the wall. At the distance of 60 pacesfrom the angle is a square bastion, and near it is a large breach in the wall; from thesquare bastion, about 120 paces, is a round bastion, and next stands the gateway, nowcalled the water-gate, which only communicates with the land at low water, and leads tothe High Street; the arch of this gateway is pointed, about 8 feet in width, and defended oneach hand by angular terraces, with fronts projecting, a figure not commonly met with inold fortifications. From this gate the wall advances to, and abuts upon, the rock near itspoint, where the pier and mole begins; the whole of this south part being much moremodern than the north and west sides.”
Bishop Pudsey, in the year 1189, probably raised the walls and increased the forti-fications of Hartlepool, and by the Normans it was always held as an important place ofsecurity.
The docks were greatly improved by the late Mr. Rennie ; a considerable sum of moneylias since been expended upon them, and they aft'ord us now one of the best examples of asluicing harbour that exists. The eastern dock next the entrance is 460 feet wide, the westdock 230 feet wide next the entrance, and 1075 feet in length, and the tidal harbourupwards of 700 feet in width, between the slake bank and quay wall.
The scouring sluice and tunnels between the slake and the tidal harbour were built in amost admirable manner ; the channel for the water was 15 feet in width, having a flat archat bottom as an invert, 22 inches in thickness, and another above, to cover the watercourse,
2 feet 3 inches deep, rising about 18 inches. The height of the side walls, between thespringing of the top and bottom arch was 4 feet, and their thickness 5 feet 6 inches. Theside walls, throughout their entire length, were further strengthened by external buttresses,
3 feet 6 inches thick, and 4 feet projection.
Sheeting piles were driven in at each end of the sluice, and also under the sluice gates orpaddles. The entire foundation of the tunnel was floored with 3-inch plank, laid on stouttimbers. The gates of the sluice arc of cast-iron, lifted by well-arranged machinery, andthe whole is made to operate most effectively.
The retaining walls have a curved face, the radius from which they arc struck being 80feet. The toe of the wall in the interior of the dock is 5 feet below low water, and thoseof the quay next the tide harbour 7 feet. The exterior quay walls are founded on piles,well protected, and carried up with excellent stone in regular courses, and coped through-out with stone 3 feet 6 inches in width. Oak fenders, 12 inches by 10, are fixed oppositeeach counterfort, at a level of 6 feet above low water, strong iron shoes being cast to retainthem.
The retaining walls of the docks are at the base 12 feet in width, and diminish graduallyto the top, where they are only 6 feet in width. The tops of the fenders are capped withcast-iron bollards; holding down stones, with Lewis eye-bolts, are everywhere provided forthe fastening of the hawsers in a perfectly secure manner.
The bank wall between the tide harbour and the slake has a slope 4 to 1 next the tide-harbour, and 2 to 1 next the slake or reservoir, with a puddle wall carried lip in the interiorto prevent the water percolating.