1999:153 - NENDRUM, Mahee Island, Down

Since 1995 staff of the Centre for Maritime Archaeology, sponsored by the Environment and Heritage Service, have been carrying out an archaeological survey of the intertidal zone of Strangford Lough. The survey revealed sites of many periods from the Mesolithic up to the present relating to the submerged landscape, defence, communications and economic exploitation of the shore. Many of these sites, however, have little or no parallel, and excavation is required to decide the nature of the site and to which period it belongs. One such site was an area beside the ancient monastic settlement site of Nendrum on Mahee Island, marked 'pond' on the OS 1:2500 map. The excavation was undertaken in an attempt to determine the function and date of this 'pond' as part of an ongoing series of investigations within the Strangford Lough intertidal zone.

The excavation revealed that this was not a fishpond but a millpond for a horizontal mill of the Early Christian period. This site differs from most of other horizontal mills in that it is a tide mill, which uses the flow of the tide to fill the millpond and the water released from the millpond to drive the wheel when the tide has receded. Only one other tide mill of this period has so far been found in Ireland (at Little Island, Co. Cork). Three mills had been constructed on the site, with the linear stone wall representing the final phase.

The only visible evidence of the Phase 1 mill is the substantial drystone feature with two gaps aligned roughly north-west/south-east across the bay. Excavation revealed a revetment of vertical timbers with horizontal planking held in place by a series of wattle walls (three to date) and the badly disturbed remains of a wheelhouse, including a badly eroded wooden flume (left in situ), associated with this millpond bank. This mill has been dated by dendrochronology to AD 619.

No structural remains of the Phase 2 mill-house or wheelhouse survived, but excavation revealed evidence of its millpond walls. No date has so far been obtained for this phase of the complex. A large beam uncovered during the excavation was sampled for dating by dendrochronology, but a good match has not yet been found. It is proposed to take further samples from other timbers in an attempt to obtain a firm date for the second mill.

Phase 3 saw the mill replaced by a third mill comprising a millpond on an east-west alignment, a large stone flume and a drystone-built wheelhouse. Drystone-built wheelhouses are not uncommon in Ireland, but the stone flume at the time of writing is unique. The flume had been constructed from two large sandstone blocks chiselled out and butt-jointed within the back wall of the wheelhouse. Immediately above the floor of the wheelhouse was a layer of silt containing souterrain ware, two bone pins, discarded timbers and the remains of wattle screens. Two millstones and three horizontal wheel paddles were also recovered from this layer. The lower millstone was complete and still retained the bush to allow the shaft to pass through to the upper stone. The upper millstone had been broken before deposition and was recovered in three fragments with a small portion missing. This mill has been dated by dendrochronology to late AD 788/early 789.

Most of the artefacts recovered from the excavation were wooden, ranging from small chips, pegs and wedges to substantial squared timbers up to 2.5m long. Among the larger pieces are a horizontal mill hub and shaft, a possible second hub, an oar/paddle, a possible second oar and several mill fittings. The remains of a lathe-turned wooden bowl were found in the silted-up flume of the third-phase mill. Flint artefacts and struck flakes, clearly residual, were scattered throughout the excavated area. Other small finds recovered were a bronze buckle, two possible whetstone fragments, iron-working slag, tuyere fragments and an amber bead. Animal bones and teeth were recovered from many of the deposition layers.

A second season is planned for early spring 2000.

5–33 Hill Street, Belfast BT1 2LA