Evidence for town defences has been found at Dublin, Waterford and Limerick. The Dublin evidence for town defences is the earliest and most complete found to date. It is clear that Dublin was enclosed by an earthen bank in the 10th century and that a larger second bank was built outside this around the 11th-century town. It also appears that according as the latter bank was being enlarged, especially by the addition of layers of estuarine mud in the 11th century, a stone revetment was placed in front of it. It seems that in places this wall was more than a facade and was a free standing town wall. Both Dublin and Waterford were encircled by such walls in the Hiberno-Norse period. Limerick’s bank may have been stone-faced; Wexford appears to have been defended by a stone wall at the time of the Norman Invasion.
The most extensive series of defences were excavated at Fishamble Street, Dublin among a succession of nine waterfronts along the south bank of the River Liffey. These waterfronts included two possible flood banks and two definitely defensive embankments which date from the Viking period and a stone wall of about 1100. The earliest embankments were low and non-defensive and were located above high-water line. They were not more than 1m high and do not appear to have been palisade. It is not clear how much of the settlement they encircled. Their primary function was to keep dry the properties on the sloping ground above the foreshore where there is some evidence for the accumulation of possible yard detritus before the construction of the embankments. Some time later in the 10th century an extensive embankment was erected along the high-water line. This appears to have been built in a number of sections although probably conceived as a unit and probably erected by royal authority. It was built on top of dumped organic refuse and was established by a pre-existing fence. The bank was bonded in mud and its location on a naturally rising slope made its external aspect higher than its internal. It was protected from the erosive action of the tidal river by a breakwater which was secured in a channel cut into the rocky foreshore. A cobbled stone pathway existed inside and parallel to the bank along the western stretch and towards Fishamble Street. A ditch, 1.6m deep and 2m wide, was cut into the natural limestone immediately outside part of the bank. A series of planks were set edge-to-edge on the outer slope of this part of the bank, each with a large mortise through which they were probably originally pegged to the bank. These planks appear to have been intended to provide a smooth beaching/docking slipway for ships or, less likely, they may have been the surviving lowest part of a palisade erected on the forward slope of the bank. This first defensive Viking embankment seems to have encircled the whole town because it appears also to be represented in Ross Road on the south side.
Little time elapsed between the abandonment of the first bank and its replacement by its successor, which in places incorporated the earlier structure. A second larger embankment was built in at least four different stages and erected at the river - ward side of its predecessor, probably around the year 1000. Gravel, stones and earth were used in its construction, the dumped layers being rein forced by discarded post-and-wattle screens and by layers of brushwood. At one stage in its history this bank was crowned by a post-and-wattle palisade; later, when the bank was heightened, a more robust stave wall, anchored from behind, was placed on top. In its final phase, this bank was covered over with estuarine mud brought from the bed of the river; this dried out and formed a firm surface. This second defensive embankment also encircled the whole town. It too appears at Ross Road as well as on two sides of Dublin Castle, in the Powder Tower, where the eastern ramparts of the Viking town were unearthed with a short southern stretch west of the Birmingham Tower. Part of its eastern stretch may also have turned up in Parliament Street, where the defences overlooked the west bank of the Poddle. It seems that an even higher bank was erected before the construction of the stone wall.
It is likely that for a considerable part of the Hiberno- Norse period Dublin was encircled by the earthen embankments just described. Towards the end of the 11th century a stone wall about 1.5 m wide and possibly as much as 3.5 m in original height was built outside these embankments. The average surviving height of the wall was about 2 m along Wood Quay, across which over 100 m of wall was uncovered. The wall was composed of a rubble fill within mortared stone facings. A number of splits in the coursing of the inner face of the wall indicated that the outer face might have been built first and the wall completed on the inside. It seems that the wall was not meant to be completely free-standing and that its lowest part may have been a revetment or quay wall which fronted a bank of organic and mud layers dumped behind it. The recent discovery of a long stretch of this wall at Ross Road in the southern part of the Hiberno-Norse town strongly suggests that this wall also encircled the whole town. It is possible that the reason the Dún of Dublin was marvelled at as one of the wonders of Ireland in a poem about 1120 in the Book of Leinster was because this stone wall was a relatively new feature at that time.
The development of Waterford’s defences seems to parallel the Dublin experience. However, it was only after the expansion of the town that embankments were added and this was well into the 11th century. About 35 m of the 11th-century earthen bank have been exposed in four separate excavations. This bank was accompanied by a ditch, which varied in depth between 2 and 2.5 m and was 2.5 m wide at the base. The bank is described as ‘substantial’ and was made of turfs interleaved with clay and was up to 4 m in width, the original height probably being in excess of 3 m (surviving to a height of 1.65 m). The bank was built in sections by gangs of workmen under the control of some municipal authority. Interestingly, oak beams ‘may have formed some sort of superstructure on the bank’ and these have been dated to 1070-90. Planks on the front face of the first defensive bank at Fishamble Street, Dublin present a possible parallel.
In the second quarter of the 12th century the bank was demolished and the ditch backfilled to accommodate a substantial stone wall of which 22 m survived to a maximum height of 1.65 m or 8 courses of construction. The wall was built as a revetment against the eastern half of the bank and, according to the excavator, was never entirely free - standing. Like the Hiberno-Norse wall around Dublin, it had a projecting footing and was slightly battered. It had a rubble core and was built in different sections with vertical joints appearing between these sections; all of this finds parallels in the Dublin wall. There was a cobble pathway outside the wall.
Uniquely to date, the Waterford excavations also produced evidence for a pre-Norman gateway. This was at Peter Street, where the outer face of a 1.72 m wide gateway in the town wall exposed. It consisted of ‘two ashlars built jambs… above projecting plinths’ which survived to a height of 3 and 4 courses.
What was described as a 10.1 m stretch of a ‘clay bank riveted by a limestone wall’ turned up at the King John’s Castle site, Limerick. It had a maxi - mum surviving height of 1.7 m and had a 1m wide pathway on a berm at its base, beyond which was 2.8 m deep ditch. It is thought that these features may represent the south side of a ‘massive stone-riveted earthen rampart which, from the associated finds, may date to the 12th century.’ That this ‘earlier structure was utilised in the Norman defences for a limited duration’ was confirmed by the discovery of its being bonded to the later, mortared east curtain wall of the castle.
There is no archaeological confirmation to date for the Viking Age defensive embankment pro - posed for Wexford. The Bride Street excavations revealed no trace of a bank. The absence of banks from the relatively closely located Bride Street and Oyster Lane excavations could mean that Wexford was not defended by a bank along its 11th-century waterfront. The surviving walls of Wexford seem to date much later. Giraldus Cambrensis uses the term murum for Wexford’s defences, a term he also uses for the town walls of Dublin, Waterford and Limerick which implies that the towns in quest - ion were each defended by stone walls before the coming of the Anglo-Normans in the 12th century.
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