2001:708 - KILKENNY: NOR-2, Mill Island and Green’s Bridge Weir, Kilkenny

Introduction
An excavation of part of a mill known locally as Mill Island and the associated Green’s Bridge Weir was carried out between June and October 2001, following land-based assessments in 2000 (Excavations 2000, No. 544, 00E0390). The site lies immediately downstream of Green’s Bridge in Kilkenny City, and forms part of a larger milling complex made up of Chancellors Mills, Bishops Mill and Green’s Bridge Weir. Proposed development involves the complete removal of Mill Island and Green’s Bridge Weir.

Background
Mill Island forms part of the milling complex known as Bishops Mills, lying on the left bank of the Nore on the site of the present Peace Park. Bishops Mills lay on a 2.2km-long mill-race, running from Newpark to Maudlin Mills. A mill was recorded on this site in 1398, and as ‘Bishop’s Mill’ in 1430 (Bradley 2000, 17). However, John Bradley (pers. comm.) suggests that the ecclesiastical association of this site may point to a pre-Norman origin. Two cornmills are recorded in the 1654 Civil Survey, although not marked on the 1655 Down Survey map. A small building is marked on Pratt’s ‘View of Kilkenny’ of 1708, and a rectangular mill building and tail-race are recorded on Rocque’s map of 1758. The weir is not shown on the Robertson Plan of 1800. But both the island and the weir are recorded on the 1840–1 (first edition) Ordnance Survey six-inch map as corn and tuck mills. This map also shows mill buildings at the northern extent of the island, a long ‘tenters’ area to the south and a ‘Summer House’ building at the southern tip. The mill continued to be referred to as ‘corn mills’ until its demolition in 1982.

Archaeological results
Mill Island (site code NOR-4) lies on the left (east) bank of the Nore and is a long narrow island, cut off from the left bank by a small mill-race. The island is 90m long, 5m wide and c. 5m deep and is revetted by stone walls on either side, with evidence for a sluice-gate and surviving wheel pit. The eastern half of this mill complex was not investigated as it lay under the Peace Park and therefore outside the limits of this development.

Green’s Bridge Weir links both sides of the river and is a large V-shaped stone weir, spanning the river channel. The weir (but not the mill) is recorded on the Urban Archaeological Survey (Ref. Map 4a: 41), which described it as possibly dating from the 17th century, but may have replaced an earlier timber weir. Both sites are recorded in the Industrial Survey of Kilkenny. The weir is V-shaped, with a 35° angle crossing a 24m-wide stretch of river. Each arm measures 72–75m in length. The eastern arm is breached.

Full excavation involved an open-area excavation of the island and cuttings opened in areas normally underwater that were dammed from the river and de-watered. For the purposes of excavation the site was broken down into six areas.
• Areas 1 and 2 related to Green’s Bridge Weir on the left and right bank respectively.
• Area 3 is the milling machine-rooms.
• Area 4 is the long tongue of land to the south of Area 3 described as a ‘tenters’ area.
• Area 5 is the southern tip of Mill Island, described as ‘Summer House’.
• Area 6 is the associated water-wheel pit area immediately east of Area 3.

No work was undertaken on Area 2 this year, but Areas 4 and 5 were resolved. Further work will be required for full mitigation in Areas 1, 3 and 6. The results of excavation are summarised below.

Area 1: Green’s Bridge Weir (left bank)
Excavation of the left (eastern) arm of Green’s Bridge Weir was undertaken in low water by means of a single open-area cutting and using small water-pumps. Opened within the weir structure, the trench was 13.5m long and 5.4m wide. This cutting exposed the upstream side and main body of the weir, but retained a 2m-wide section of the downstream toe as a baulk and retaining wall to the river. The downstream toe was investigated underwater by divers from ADCO Ltd. Excavation revealed two phases of activity at this site.

Phase 1 was a row of 32 vertical timber roundwood stakes, with two associated large horizontal trimmed tree trunks, orientated north-east/south-west and measuring 12.5m in length by c. 0.85 in width (41–39.7+m OD). The timber feature appeared to terminate to the north and represents a deflection dam arrangement for the left-bank mill, pre-dating the 18th-century construction of the weir, and possibly dates from the late medieval or early post-medieval period. A sample of this will give a more accurate date but cannot be retrieved until summer water-levels.

Phase 2 was dated artefactually to the late 18th/early 19th century and was an earthen rubble core faced with limestone water-worn pitching stones, revetted on both sides by a line of small oak roundwood stakes. The weir was on a slightly different alignment to Phase 1 and spanned the full width of the river (into Area 2). The eastern arm was heavily truncated by modern deliberate destruction in the 1960s and was 29.5m long, 7.2m wide and 1.65m high (42.6–40.6m OD). The core of the weir overlay Phase 1 and was a basal bank of fine river gravels and large unshaped angular boulders of black Kilkenny ‘marble’, containing a large carved oak plank. This was sealed by a layer of mixed sand and clay, and lined by water-worn trapezoidal-shaped limestone blocks, 0.4m in diameter.

Area 3: Mill Island
Mill Island contained four mill buildings, Rooms A–D (collectively Area 3). Excavation revealed at least three phases of milling activity in Area 3, and further investigation of the lower levels will be required to mitigate the proposed development of this site.

Room A (Phase 1) represented the northernmost building in Area 3, and also the earliest phase of milling. This was a heavily truncated rectangular building of drystone or poorly mortared limestone rubble revetment walls, 6m+ long (north–south) by 3m wide, and built directly on river gravels (42.27–41.85m+ OD), retaining the riverbank. This phase may relate to the Tudor or medieval phase of this mill, but could not be fully investigated and no dating evidence was recovered.

Phase 2 related to the construction of the surviving upstanding walls of Area 3. This required the extension of the island west into the Nore by up to 2m. At this stage the original river revetment wall had silted up by this width and construction of the outer riverside walls cut into the river silt. The foundations of the walls of this site were not investigated but the wall trench was backfilled with stone rubble and mortar. It is likely that the revetment of Area 4 was also undertaken.

Room A was a rectangular structure, 11.5m long (north–south) by 5.2m and 3.3m+ high. Room B was immediately south of and contemporary with Room A, and was 5.7m long (north–south) by 4.95m wide. Room C was bonded to the southern wall of Room B and was 9.7m long (north–south) with a tapering width of 4.75m. All three buildings spanned the expanded width of Area 3 and were constructed of mortared random rubble limestone, with brick-lined opes. Room D adjoined the southern end of Room C, with the western wall constructed of limestone random rubble with two buttresses. The eastern side of this room was open and two limestone mortared pillars, resting on reused millstones (one a local grit bed-stone, the other an 1870+ French burrstone), presumably supported a hanging first floor. This room contained brick-lined kilns, for drying corn (evidenced by large quantities of air-brick recovered from this phase, and probably from a first-floor level).

During this phase of construction a heavily truncated cobbled floor, 1m square, within Room A (at 42.32m OD) was revealed in excavation. This floor was built on a mortar rubble foundation and appears to have been deliberately dismantled. This may correspond with the flooding of the mill, as a direct result of the construction of the Ormond and Lacken weirs, downstream.

At some point during the late 18th/early 19th century, Ormond Weir’s construction raised the water-level downstream of Green’s Weir and flooded Mill Island. This required the floor levels of the building to be raised by 0.75m (Phase 3). Rooms C and D had hard-packed clay floors at this level, whereas a fine cobbled floor was built across Rooms A and B (43.32m OD), with an associated machine-pit at the north-east corner of Room A, 1.9m long (east–west), 1.6m wide and 1.1m deep. This was built from cut limestone blocks, and some reused Tudor masonry fragments, and housed the gearing mechanism for the millstones. Room B also contained fuel and iron slag dumps. The presence of industrial waste in a shallow pit within Room C may also be associated with the kilns.

Area 4
This area of Mill Island was immediately south of Room D, Area 3, and was 59m long, 4.5m wide and 1.5–2.2m high. This area was in situ riverbank, revetted on both sides by a 0.45m-wide drystone rubble wall. The partially levelled walls and original ground surface were sealed by 0.3m of imported sterile sand and gravel, containing iron slag dumps and numerous large iron mill machinery parts, including gearwheels, cogs and axles. No evidence remained of the tenters.

Area 5
Area 5 was the southern tip of Mill Island, immediately south of Area 4. The island terminates in a semi-pointed arc of rubble revetment wall; however, the area was noted on the first edition of the 25in. Ordnance Survey map (1872) as a ‘Summer House’. Although excavation revealed no evidence of a dwelling structure at this location, two phases of construction were exposed.

Phase 1 was a flat-ended terminus wall, built on a flagstone foundation of mortared random rubble limestone (0.45m thick) and revetted by large oak roundwoods, 0.2m in diameter. This may have proved to be structurally unsound in such a fast-flowing river, so the terminus was extended in Phase 2 with a roughly tapered drystone wall addition, adding a further 5m on to the length of the island. This too was revetted by large timber roundwoods.

Area 6
Immediately east of Room A, Area 3, were two narrow deep channels for the two independent water-wheels, an upstream sluice-gate and associated downstream tail-race channel. The River Nore was directed by Green’s Bridge Weir to the left-bank sluice-gate, and immediately upstream of the sluice-gate was a cut-water, which directed a smooth flow of water to the two water-wheels. This cut-water was 1.1m long by 1.1m wide and was constructed of limestone blocks.

The sluice-gate was no longer present but its stone settings survived. The gate ran the width of the channel (3m east–west) and was 90mm wide. Fine cut-limestone mouldings were noted on both channel walls, with a later replacement concrete and timber base-plate.

Each water-wheel was housed in a stone-lined pit, 5.5m long, 0.75m wide and 2.2m deep (41.22m OD). This was lined at the base with large water-worn flagstones. The inside axle of both wheels ran directly into the machine-pits of each mill (east to Room A and west into the baulk), while the outside axle rested on a truncated limestone masonry pier which abutted the upstream sluice-gate and cut-water. This masonry pier was constructed of large mortared cut limestone facing a core of stone rubble and timber piles. It was 10.2m long (downstream of the sluice-gate), 1.32m wide, tapering to a point south of the water-wheels, and 0.45m in truncated depth. The wear pattern on the outer walls could be used to extrapolate that the water-wheels were 4.4m in diameter and 0.75m in width.

Conclusions
Excavation of this site revealed a multi-phase industrial corn-milling complex and weir dating from the early 19th century, with limited evidence of earlier undated structures under both. Evidence for corn-grinding and metalworking has already been identified. A sizeable assemblage of industrial and early modern artefacts, machinery parts, timber and Tudor cut stone has been recovered to date, together with a full record of the fabric and archaeological deposits of the upper levels of this site. However, further work will be required in low-water summer conditions for complete resolution, in order to mitigate its scheduled removal as part of this development. It is hoped that dendrochronology samples can be retrieved from Green’s Bridge Weir, and further artefactual and morphological study of this site will reveal the earliest phase(s) of the mill, possibly uncovering the source of the Tudor stone artefacts. The full study of this site will take some time and analysis is only at a preliminary stage; however, it is clear that this excavation represents an important addition to local and regional industrial architectural and archaeological research.

Reference
Bradley, J. 2000 Irish Historic Towns Atlas, Kilkenny. Dublin.

2 Killiney View, Albert Road Lower, Glenageary, Co. Dublin